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Astronomy Picture of the Day
Search Results for "Milky Way"




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Thumbnail image of picture found for this day. APOD: 2021 December 21 - Solstice Sun and Milky Way
Explanation: Welcome to December's solstice, first day of winter in the north and summer for the southern hemisphere. Astronomical markers of the seasons, solstice and equinox dates are based on the Sun's place in its annual journey along the ecliptic, through planet Earth's sky. At this solstice, the Sun reaches its maximum southern declination of -23.5 degrees today at 15:59 UTC, while its right ascension coordinate on the celestial sphere is 18 hours. That puts the Sun in the constellation Sagittarius in a direction near the center of our Milky Way galaxy. In fact, if you could see today's Solstice Sun against faint background stars and nebulae (that's really hard to do, especially in the daytime ...) your view might look something like this composited panorama. To make it, images of our fair galaxy were taken under dark Namibian night skies, then stitched together in a panoramic view. From a snapshot made on 2015 December 21, the Sun was digitally overlayed as a brilliant star at today's northern winter solstice position, close to the center of the Milky Way.

Thumbnail image of picture found for this day. APOD: 2021 November 1 - A Waterfall and the Milky Way
Explanation: The dream was to capture both the waterfall and the Milky Way together. Difficulties included finding a good camera location, artificially illuminating the waterfall and the surrounding valley effectively, capturing the entire scene with numerous foreground and background shots, worrying that fireflies would be too distracting, keeping the camera dry, and avoiding stepping on a poisonous snake. Behold the result -- captured after midnight in mid-July and digitally stitched into a wide-angle panorama. The waterfall is the picturesque Zhulian waterfall in the Luoxiao Mountains in eastern Hunan Province, China. The central band of our Milky Way Galaxy crosses the sky and shows numerous dark dust filaments and colorful nebulas. Bright stars dot the sky -- all residing in the nearby Milky Way -- including the Summer Triangle with bright Vega visible above the Milky Way's arch. After capturing all 78 component exposures for you to enjoy, the photographer and friends enjoyed the view themselves for the rest of the night.

Thumbnail image of picture found for this day. APOD: 2021 October 1 - The Central Milky Way from Lagoon to Pipe
Explanation: Dark markings and colorful clouds inhabit this stellar landscape. The deep and expansive view spans more than 30 full moons across crowded star fields toward the center of our Milky Way Galaxy. Cataloged in the early 20th century by astronomer E. E. Barnard, the obscuring interstellar dust clouds seen toward the right include B59, B72, B77 and B78, part of the Ophiuchus molecular cloud complex a mere 450 light-years away. To the eye their combined shape suggests a pipe stem and bowl, and so the dark nebula's popular name is the Pipe Nebula. Three bright nebulae gathered on the left are stellar nurseries some 5,000 light-years distant toward the constellation Sagittarius. In the 18th century astronomer Charles Messier included two of them in his catalog of bright clusters and nebulae; M8, the largest of the triplet, and colorful M20 just above. The third prominent emission region includes NGC 6559 at the far left. Itself divided by obscuring dust lanes, M20 is also known as the Trifid. M8's popular moniker is the Lagoon Nebula.

Thumbnail image of picture found for this day. APOD: 2021 September 6 - Firefly Milky Way over Russia
Explanation: It started with a pine tree. The idea was to photograph a statuesque pine in front of the central band of our Milky Way Galaxy. And the plan, carried out two months ago, was successful -- they both appear prominently. But the resulting 3-frame panorama captured much more. Colorful stars, for example, dot the distant background, with bright Altair visible on the upper left. The planet Saturn, a bit closer, was captured just over the horizon on the far left. Just beyond the Earth's atmosphere, seen in the upper right, an Earth-orbiting satellite was caught leaving a streak during the 25-second exposure. The Earth's atmosphere itself was surprisingly visible -- as green airglow across the image top. Finally, just by chance, there was a firefly. Do you see it? Near the image bottom, the firefly blinked in yellow several times as it fluttered before the rolling hills above Milogradovka River in Primorsky Krai, Russia.

Thumbnail image of picture found for this day. APOD: 2021 August 3 - A Perseid Meteor and the Milky Way
Explanation: It was bright and green and flashed as it moved quickly along the Milky Way. It left a trail that took 30 minutes to dissipate. Given the day, August 12, and the direction, away from Perseus, it was likely a small bit from the nucleus of Comet Swift-Tuttle plowing through the Earth's atmosphere -- and therefore part of the annual Perseids meteor shower. The astrophotographer captured the fireball as it shot across the sky in 2018 above a valley in Yichang, Hubei, China. The meteor's streak, also caught on video, ended near the direction of Mars on the lower left. Next week, the 2021 Perseids meteor shower will peak again. This year the Moon will set shortly after the Sun, leaving a night sky ideal for seeing lots of Perseids from dark and clear locations across planet Earth.

Thumbnail image of picture found for this day. APOD: 2021 July 3 - Along the Milky Way
Explanation: You can't walk along the Milky Way. Still, under a dark sky you can explore it. To the eye the pale luminous trail of light arcing through the sky on a dark, moonless night does appear to be a path through the heavens. The glowing celestial band is the faint, collective light of distant stars cut by swaths of obscuring interstellar dust clouds. It lies along the plane of our home galaxy, so named because it looks like a milky way. Since Galileo's time, the Milky Way has been revealed to telescopic skygazers to be filled with congeries of innumerable stars and cosmic wonders.

Thumbnail image of picture found for this day. APOD: 2021 May 27 - Mid-Eclipse and Milky Way
Explanation: May's perigee Full Moon slid through Earth's shadow yesterday entertaining night skygazers in regions around the Pacific. Seen from western North America, it sinks toward the rugged Sierra Nevada mountain range in this time-lapse series of the total lunar eclipse. Low on the western horizon the Moon was captured at mid-eclipse with two separate exposures. Combined they reveal the eclipsed Moon's reddened color against the dark night sky and the diffuse starlight band of the Milky Way. Frames taken every five minutes from the fixed camera follow the surrounding progression of the eclipse partial phases. In the foreground a radio telescope dish at California's Owens Valley Radio Observatory points skyward.

Thumbnail image of picture found for this day. APOD: 2021 January 22 - The Milky Ring
Explanation: An expanse of cosmic dust, stars and nebulae along the plane of our Milky Way galaxy form a beautiful ring in this projected all-sky view. The creative panorama covers the entire galaxy visible from planet Earth, an ambitious 360 degree mosaic that took two years to complete. Northern hemisphere sites in western China and southern hemisphere sites in New Zealand were used to collect the image data. Like a glowing jewel set in the milky ring, the bulge of the galactic center, is at the very top. Bright planet Jupiter is the beacon just above the central bulge and left of red giant star Antares. Along the plane and almost 180 degrees from the galactic center, at the bottom of the ring is the area around Orion, denizen of the northern hemisphere's evening winter skies. In this projection the ring of the Milky Way encompasses two notable galaxies in southern skies, the large and small Magellanic clouds.

Thumbnail image of picture found for this day. APOD: 2020 November 17 - A Glowing STEVE and the Milky Way
Explanation: What's creating these long glowing streaks in the sky? No one is sure. Known as Strong Thermal Emission Velocity Enhancements (STEVEs), these luminous light-purple sky ribbons may resemble regular auroras, but recent research reveals significant differences. A STEVE's great length and unusual colors, when measured precisely, indicate that it may be related to a subauroral ion drift (SAID), a supersonic river of hot atmospheric ions thought previously to be invisible. Some STEVEs are now also thought to be accompanied by green picket fence structures, a series of sky slats that can appear outside of the main auroral oval that does not involve much glowing nitrogen. The featured wide-angle composite image shows a STEVE in a dark sky above Childs Lake, Manitoba, Canada in 2017, crossing in front of the central band of our Milky Way Galaxy.

Thumbnail image of picture found for this day. APOD: 2020 October 11 - Milky Way over the Pinnacles in Australia
Explanation: What strange world is this? Earth. In the foreground of the featured image are the Pinnacles, unusual rock spires in Nambung National Park in Western Australia. Made of ancient sea shells (limestone), how these human-sized picturesque spires formed remains unknown. In the background, just past the end of the central Pinnacle, is a bright crescent Moon. The eerie glow around the Moon is mostly zodiacal light, sunlight reflected by dust grains orbiting between the planets in the Solar System. Arching across the top is the central band of our Milky Way Galaxy. Many famous stars and nebulas are also visible in the background night sky. The featured 29-panel panorama was taken and composed in 2015 September after detailed planning that involved the Moon, the rock spires, and their corresponding shadows. Even so, the strong zodiacal light was a pleasant surprise.

Thumbnail image of picture found for this day. APOD: 2020 September 7 - The Milky Way over St Michaels Mount
Explanation: Where do land and sky converge? On every horizon -- but in this case the path on the ground leads to St Michael's Mount (Cornish: Karrek Loos yn Koos), a small historic island in Cornwall, England. The Mount is usually surrounded by shallow water, but at low tide is spanned by a human-constructed causeway. The path on the sky, actually the central band of our Milky Way Galaxy, also appears to lead to St Michael's Mount, but really lies far in the distance. The red nebula in the Milky Way, just above the castle, is the Lagoon Nebula, while bright Jupiter shines to the left, and a luminous meteor flashes to the right. The foreground and background images of this featured composite were taken on the same July night and from the same location. Although meteors are fleeting and the Milky Way disk shifts in the night as the Earth turns, Jupiter will remain prominent in the sunset sky into December.

Thumbnail image of picture found for this day. APOD: 2020 August 17 - Perseids Around the Milky Way
Explanation: Why would meteor trails appear curved? The arcing effect arises only because the image artificially compresses (nearly) the whole sky into a rectangle. The meteors are from the Perseid Meteor Shower that peaked last week. The featured multi-frame image combines not only different directions from the 360 projection, but different times when bright Perseid meteors momentarily streaked across the sky. All Perseid meteors can be traced back to the constellation Perseus toward the lower left, even the seemingly curved (but really straight) meteor trails. Although Perseids always point back to their Perseus radiant, they can appear almost anywhere on the sky. The image was taken from Inner Mongolia, China, where grasslands meet sand dunes. Many treasures also visible in the busy night sky including the central arch of our Milky Way Galaxy, the planets Saturn and Jupiter toward the right, colorful airglow on the central left, and some relatively nearby Earthly clouds. The Perseid Meteor Shower peaks every August.

Thumbnail image of picture found for this day. APOD: 2020 June 17 - Magnetic Streamlines of the Milky Way
Explanation: What role do magnetic fields play in interstellar physics? Analyses of observations by ESA's Planck satellite of emission by small magnetically-aligned dust grains reveal previously unknown magnetic field structures in our Milky Way Galaxy -- as shown by the curvy lines in the featured full-sky image. The dark red shows the plane of the Milky Way, where the concentration of dust is the highest. The huge arches above the plane are likely remnants of past explosive events from our Galaxy's core, conceptually similar to magnetic loop-like structures seen in our Sun's atmosphere. The curvy streamlines align with interstellar filaments of neutral hydrogen gas and provide tantalizing evidence that magnetic fields may supplement gravity in not only in shaping the interstellar medium, but in forming stars. How magnetism affected our Galaxy's evolution will likely remain a topic of research for years to come.

Thumbnail image of picture found for this day. APOD: 2020 May 26 - The Milky Way over Snow Capped Himalayas
Explanation: What’s higher than the Himalayas? Although the Himalayan Mountains are the tallest on planet Earth, they don't measure up to the Milky Way. Visible above the snow-capped mountains in the featured image is the arcing central band of our home galaxy. The bright spot just above the central plane is the planet Jupiter, while the brightest orange spot on the upper right is the star Antares. The astrophotographer braved below-zero temperatures at nearly 4,000-meters altitude to take the photographs that compose this image. The featured picture is a composite of eight exposures taken with same camera and from the same location over three hours, just after sunset, in 2019 April, from near Bimtang Lake in Nepal. Over much of planet Earth, the planets Mercury (faint) and Venus (bright) will be visible this week after sunset.

Thumbnail image of picture found for this day. APOD: 2020 May 20 - Moon, Mars, Saturn, Jupiter, Milky Way
Explanation: It is not a coincidence that planets line up. That's because all of the planets orbit the Sun in (nearly) a single sheet called the plane of the ecliptic. When viewed from inside that plane -- as Earth dwellers are likely to do -- the planets all appear confined to a single band. It is a coincidence, though, when three of the brightest planets all appear in nearly the same direction. Such a coincidence was captured about a month ago. Featured above, Earth's Moon, Mars, Saturn, and Jupiter were all imaged together, just before sunrise, from the Black Sea coast of Bulgaria. A second band is visible diagonally across this image -- the central band of our Milky Way Galaxy. If you wake up early, you will find that these same planets remain visible in the morning sky this month, too.

Thumbnail image of picture found for this day. APOD: 2020 April 21 - Eye on the Milky Way
Explanation: Have you ever had stars in your eyes? It appears that the eye on the left does, and moreover it appears to be gazing at even more stars. The featured 27-frame mosaic was taken last July from Ojas de Salar in the Atacama Desert of Chile. The eye is actually a small lagoon captured reflecting the dark night sky as the Milky Way Galaxy arched overhead. The seemingly smooth band of the Milky Way is really composed of billions of stars, but decorated with filaments of light-absorbing dust and red-glowing nebulas. Additionally, both Jupiter (slightly left the galactic arch) and Saturn (slightly to the right) are visible. The lights of small towns dot the unusual vertical horizon. The rocky terrain around the lagoon appears to some more like the surface of Mars than our Earth.

Thumbnail image of picture found for this day. APOD: 2020 March 9 - Milky Way and Zodiacal Light over Chile
Explanation: What is the band of light connecting the ground to the Milky Way? Zodiacal light -- a stream of dust that orbits the Sun in the inner Solar System. It is most easily seen just before sunrise, where it has been called a false dawn, or just after sunset. The origin of zodiacal dust remains a topic of research, but is hypothesized to result from asteroid collisions and comet tails. The featured wide-angle image shows the central band of our Milky Way Galaxy arching across the top, while the Large Magellanic Cloud (LMC), a satellite galaxy to our Milky Way, is visible on the far left. The image is a combination of over 30 exposures taken last July near La Serena among the mountains of Chile. During the next two months, zodiacal light can appear quite prominent in northern skies just after sunset.

Thumbnail image of picture found for this day. APOD: 2020 January 29 - Milky Way over Yellowstone
Explanation: The Milky Way was not created by an evaporating lake. The pool of vivid blue water, about 10 meters across, is known as Silex Spring and is located in Yellowstone National Park in Wyoming, USA. Steam rises off the spring, heated by a magma chamber deep underneath known as the Yellowstone hotspot. The steam blurs the image of Jupiter, making it seem unusually large. Unrelated and far in the distance, the central band of our Milky Way Galaxy rises high overhead, a band lit by billions of stars. The featured picture is a 3-image panorama taken last August. If the Yellowstone hotspot causes another supervolcanic eruption as it did 640,000 years ago, a large part of North America would be affected.

Thumbnail image of picture found for this day. APOD: 2019 November 19 - Milky Way over Uruguayan Lighthouse
Explanation: Can a lighthouse illuminate a galaxy? No, but in the featured image, gaps in light emanating from the Jose Ignacio Lighthouse in Uruguay appear to match up nicely, although only momentarily and coincidently, with dark dust lanes of our Milky Way Galaxy. The bright dot on the right is the planet Jupiter. The central band of the Milky Way Galaxy is actually the central spiral disk seen from within the disk. The Milky Way band is not easily visible through city lights but can be quite spectacular to see in dark skies. The featured picture is actually the addition of ten consecutive images taken by the same camera from the same location. The images were well planned to exclude direct light from the famous lighthouse.

Thumbnail image of picture found for this day. APOD: 2019 October 10 - Mid-Air Meteor and Milky Way
Explanation: On September 24, a late evening commercial flight from Singapore to Australia offered stratospheric views of the southern hemisphere's night sky, if you chose a window seat. In fact, a well-planned seating choice with a window facing toward the Milky Way allowed the set up of a sensitive digital camera on a tripod mount to record the galaxy's central bulge in a series of 10 second long exposures. By chance, one of the exposures caught this bright fireball meteor in the starry frame. Reflected along the wing of the A380 aircraft, the brilliant greenish streak is also internally reflected in the double layer window, producing a fainter parallel to the original meteor track. In the southern sky Jupiter is the bright source beneath the galactic bulge and seen next to a green beacon, just off the wing tip.

Thumbnail image of picture found for this day. APOD: 2019 August 7 - Jupiter Engulfed and the Milky Way
Explanation: This is a good month to see Jupiter. To find our Solar System's largest planet in your sky, look toward the southeast just after sunset -- Jupiter should be the brightest object in that part of the sky. If you have a binoculars or a small telescope, you should be able to see Jupiter's four brightest moons right nearby, and possibly some cloud bands. The featured image was taken about a month ago from the Persian Gulf. The image shows Jupiter just to the right of the nearly vertical band of the central disk of our Milky Way Galaxy. The unnamed rock formations appear in projection like the jaws of a giant monster ready to engulf the Jovian giant. When you see Jupiter, it may be interesting to know that NASA's robotic Juno spacecraft is simultaneously visiting and studying the giant planet. Saturn is also visible this month, and although it is nearby to Jupiter, it is not as bright.

Thumbnail image of picture found for this day. APOD: 2019 June 19 - Our Galaxy's Magnetic Center
Explanation: What's the magnetic field like in the center of our Milky Way Galaxy? To help find out, NASA's SOFIA -- an observatory flying in a modified 747 -- imaged the central region with an instrument known as HAWC+. HAWC+ maps magnetism by observing polarized infrared light emitted by elongated dust grains rotating in alignment with the local magnetic field. Now at our Milky Way's center is a supermassive black hole with a hobby of absorbing gas from stars it has recently destroyed. Our galaxy's black hole, though, is relatively quiet compared to the absorption rate of the central black holes in active galaxies. The featured image gives a clue as to why -- a surrounding magnetic field may either channel gas into the black hole -- which lights up its exterior, or forces gas into an accretion-disk holding pattern, causing it to be less active -- at least temporarily. Inspection of the featured image -- appearing perhaps like a surreal mashup of impasto art and gravitational astrophysics -- brings out this telling clue by detailing the magnetic field in and around a dusty ring surrounding Sagittarius A*, the black hole in our Milky Way's center.

Thumbnail image of picture found for this day. APOD: 2019 June 17 - Milky Way over Pyramid of the Feathered Serpent
Explanation: To see the feathered serpent descend the Mayan pyramid requires exquisite timing. You must visit El Castillo -- in Mexico's Yucatán Peninsula -- near an equinox. Then, during the late afternoon if the sky is clear, the pyramid's own shadows create triangles that merge into the famous illusion of the slithering viper. Also known as the Temple of Kukulkan, the impressive step-pyramid stands 30 meters tall and 55 meters wide at the base. Built up as a series of square terraces by the pre-Columbian civilization between the 9th and 12th century, the structure can be used as a calendar and is noted for astronomical alignments. To see the central band of our Milky Way Galaxy descend overhead the Mayan pyramid, however, requires less exquisite timing. Even the ancient Mayans might have been impressed, though, to know that the exact positions of the Milky Way, Saturn (left) and Jupiter (right) in the featured image give it a time stamp more specific than equinox -- in fact 2019 April 7 at 5 am.

Thumbnail image of picture found for this day. APOD: 2019 May 27 - A Volcano of Fire under a Milky Way of Stars
Explanation: Sometimes it's hard to decide which is more impressive -- the land or the sky. On the land of the featured image, for example, the Volcano of Fire (Volcán de Fuego) is seen erupting topped by red-hot, wind-blown ash and with streams of glowing lava running down its side. Lights from neighboring towns are seen through a thin haze below. In the sky, though, the central plane of our Milky Way Galaxy runs diagonally from the upper left, with a fleeting meteor just below, and the trail of a satellite to the upper right. The planet Jupiter also appears toward the upper left, with the bright star Antares just to its right. Much of the land and the sky were captured together in a single, well-timed, 25-second exposure taken in mid-April from the side of Fuego's sister volcano Acatenango in Guatemala. The image of the meteor, though, was captured in a similar frame taken about 30 minutes earlier -- when the volanic eruption was not as photogenic -- and added later digitally.

Thumbnail image of picture found for this day. APOD: 2019 May 11 - Milky Way, Launch, and Landing
Explanation: The Milky Way doesn't look quite this colorful and bright to the eye, but a rocket launch does. So a separate deep exposure with a sensitive digital camera was used in this composite skyscape to bring out our galaxy's central crowded starfields and cosmic dust clouds. In the scene from Merritt Island National Wildlife Refuge, a nine minute long exposure begun about 20 minutes after the Miky Way image recorded a rocket launch and landing. The Falcon 9 rocket, named for the Millennium Falcon of Star Wars fame, appropriately launched a Dragon resupply ship to the International Space Station in the early morning hours of May the 4th. The plume and flare at the peak of the launch arc mark the rocket's first stage boost back burn. Two shorter diagonal streaks are the rocket engines bringing the Falcon 9 stage back to an offshore landing on autonomous drone ship Of course I Still Love You.

Thumbnail image of picture found for this day. APOD: 2019 May 10 - Halley Dust and Milky Way
Explanation: Grains of cosmic dust streaked through the mostly moonless night skies of May 7. Swept up as planet Earth plowed through the debris streams left behind by periodic Comet Halley, the annual meteor shower is known as the Eta Aquarids. Though it was made about a day after the shower's predicted maximum, this composite image still captures 20 meteors in exposures taken over a 2 hour period, registered on a background exposure of the sky. The meteor trails point back to the shower radiant near eponymous faint star Eta Aquarii close to the horizon, seen from 100 kilometers south of Sydney Australia. Known for speed, Eta Aquarid meteors move fast, entering the atmosphere at about 66 kilometers per second. Brilliant Jupiter shines near the central bulge of the Milky Way high above the horizon. The Southern Cross is just tucked in to the upper right corner of the frame.

Thumbnail image of picture found for this day. APOD: 2019 April 19 - Milky Way in Northern Spring
Explanation: A postcard from planet Earth, this springtime night skyscape looks over Alandan lake in the Alborz mountains. Taken after local midnight on April 17, the central Milky Way is rising over the region's southeast horizon. Its luminous track of stars and nebulae along the plane of our galaxy are reflected in the mirror-like lake. The brightest celestial beacon mingled with the diffuse galactic starlight is Jupiter. Slightly dimmer, Saturn is below and left just above the mountains. As spring brought leaves to the trees and the galactic center to the northern night the photographer found it also gave frogs their voices, heard like a melody across the calm water.

Thumbnail image of picture found for this day. APOD: 2019 February 8 - Moon, Four Planets, and Emu
Explanation: A luminous Milky Way falls toward the horizon in this deep skyscape, starting at the top of the frame from the stars of the Southern Cross and the dark Coalsack Nebula. Captured in the dark predawn of February 2nd from Central Victoria, Australia, planet Earth, the 26 day old waning crescent Moon still shines brightly near the horizon. The second and third brightest celestial beacons are Venus and Jupiter along the lower part of the Milky Way's central bulge. Almost in line with the brighter planets and Moon, Saturn is the pinprick of light just visible below and right of the lunar glow. Australia's first astronomers saw the elongated, bulging shape of the familiar Milky Way as a great celestial Emu. The Moon and planets could almost be the Emu's eggs on this starry night.

Thumbnail image of picture found for this day. APOD: 2019 January 14 - Meteor and Milky Way over the Alps
Explanation: Now this was a view with a thrill. From Mount Tschirgant in the Alps, you can see not only nearby towns and distant Tyrolean peaks, but also, weather permitting, stars, nebulas, and the band of the Milky Way Galaxy. What made the arduous climb worthwhile this night, though, was another peak -- the peak of the 2018 Perseids Meteor Shower. As hoped, dispersing clouds allowed a picturesque sky-gazing session that included many faint meteors, all while a carefully positioned camera took a series of exposures. Suddenly, a thrilling meteor -- bright and colorful -- slashed down right next the nearly vertical band of the Milky Way. As luck would have it, the camera caught it too. Therefore, a new image in the series was quickly taken with one of the sky-gazers posing on the nearby peak. Later, all of the images were digitally combined.

Thumbnail image of picture found for this day. APOD: 2019 January 12 - Milky Way Falls
Explanation: It can be the driest place on planet Earth, but water still flows in Chile's Atacama desert, high in the mountains. After discovering this small creek with running water, the photographer returned to the site to watch the Milky Way rise in the dark southern skies, calculating the moment when Milky Way and precious flowing water would meet. In the panoramic night skyscape, stars and nebulae immersed in the glow along the Milky Way itself also shared that moment with the Milky Way's satellite galaxies the Large and Small Magellanic clouds above the horizon at the right. Bright star Beta Centauri is poised at the very top of the waterfall. Above it lies the dark expanse of the Coalsack nebula and the stars of the Southern Cross.

Thumbnail image of picture found for this day. APOD: 2018 October 19 - Summer to Winter Milky Way
Explanation: Taken near local midnight, this autumn night's panorama follows the arch of the Milky Way across the northern horizon from the High Fens, Eifel Nature Park at the border of Belgium and Germany. Shift your gaze across the wetlands from west to east (left to right) and you can watch stars once more prominent in northern summer give way to those that will soon dominate northern winter nights. Setting, wanderer Mars is brightest at the far left, still shining against almost overwhelming city lights along the southwestern horizon. Bright stars Altair, Deneb, and Vega form the northern sky's summer triangle, straddling the Milky Way left of center. Part of the winter hexagon Capella and Aldebaran, along with the beautiful Pleiades star cluster shine across the northeastern sky. The line-of-sight along the hikers boardwalk leads almost directly toward the Big Dipper, an all season asterism from these northern latitudes. Follow the Big Dipper's pointer stars to Polaris and the north celestial pole nearly centered above it. Andromeda, the other large galaxy in the skyscape, is near the top of the frame.

Thumbnail image of picture found for this day. APOD: 2018 September 15 - Mont Blanc, Meteor, and Milky Way
Explanation: Snowy Mont Blanc is near the center of this atmospheric night skyscape. But high, thin clouds fogged the skies at the photographer's location, looking south toward Europe's highest peak from the southern Swiss Alps. Still, the 13 second exposure finds the faint star fields and dark rifts of the Milky Way above the famous white mountain. Bloated by the mist, bright planet Saturn and Antares (right), alpha star of Scorpius, shine through the clouds to flank the galaxy's central bulge. The high-altitude scene is from the rewarding night of August 12/13, so it also includes the green trail of a Perseid meteor shooting along the galactic plane.

Thumbnail image of picture found for this day. APOD: 2018 September 11 - Milky Way over Trolls Tongue
Explanation: You have to take a long hike to see the Troll's Tongue -- ten hours over rocky terrain. And in this case, it took three trips to capture the landform below a clear night sky. Trolltunga itself is a picturesque rock protrusion extending about 700 meters over mountainous cliffs near Lake Ringedalsvatnet in Norway. The overhang is made of billion-year-old Precambrian bedrock that was carved out by glaciers during an ice-age about 10,000 years ago. The featured picture is a composite of two exposures, a 15-second image of the foreground Earth followed 40 minutes later by an 87-second exposure of the background sky. Thousands of discernable stars dot the backdrop starscape in addition to billions of unresolved stars in the nearly vertical band of our Milky Way Galaxy.

Thumbnail image of picture found for this day. APOD: 2018 August 11 - Moon, Mars, and Milky Way
Explanation: Just two weeks ago, dark skies over the desert in northern Iran held this alluring celestial vista. The dramatic digital mosaic finds the Moon and Mars alongside the Milky Way's dusty rifts, stars, and nebulae. Captured through a series of exposures to cover a range in brightness, that night's otherwise Full Moon is immersed in Earth's shadow. It actually appears fainter and redder than the Red Planet itself during the widely watched total lunar eclipse. For cosmic tourists, the skyscape also includes the Lagoon (M8) and Trifid (M20) nebulae and planet Saturn shining against the Milky Way's pale starlight. The Moon isn't quite done with its shadow play, though. Today, the New Moon partially eclipses the Sun for much of northern planet Earth.

Thumbnail image of picture found for this day. APOD: 2018 July 20 - The Teapot and the Milky Way
Explanation: The recognizable stars of the Teapot asterism in the constellation Sagittarius posed with the Milky Way over Death Valley, planet Earth on this quiet, dark night. The surreal scene was appropriately captured from Teakettle Junction, marked by the wooden sign adorned with terrestrial teapots and kettles on the rugged road to Racetrack Playa. Shining against the luminous starlight of the central Milky Way is bright planet Saturn, just above the star at the celestial teapot's peak. But the brightest celestial beacon, high above the southern horizon, is an orange tinted Mars at upper left in the frame.

Thumbnail image of picture found for this day. APOD: 2018 June 9 - Countryside Mars and Milky Way
Explanation: Mars shines brightly now in planet Earth's sky. Seen with a yellowish hue it rises over the hills and far away in this serene night skyscape, a countryside panorama recorded last month from Parque Nacional de Cabaneros in Spain. The Milky Way too extends above the distant hills into a starry sky. Its faint pinkish nebulae, cosmic rifts and rivers of dust are mingled with the pale, diffuse glow of starlight. Mimicking Mars' yellow tint, bright star Antares shines to the right of the central Milky Way starclouds. Of course, CubeSats from Earth are on their way to the Red Planet.

Thumbnail image of picture found for this day. APOD: 2018 May 17 - Milky Way vs Airglow Australis
Explanation: Captured last week after sunset on a Chilean autumn night, an exceptional airglow floods this allsky view from Las Campanas Observatory. The airglow was so intense it diminished parts of the Milky Way as it arced horizon to horizon above the high Atacama desert. Originating at an altitude similar to aurorae, the luminous airglow is due to chemiluminescence, the production of light through chemical excitation. Commonly recorded in color by sensitive digital cameras, the airglow emission here is fiery in appearance. It is predominately from atmospheric oxygen atoms at extremely low densities and has often been present during southern hemisphere nights over the last few years. Like the Milky Way, on that dark night the strong airglow was very visible to the eye, but seen without color. Jupiter is the brightest celestial beacon though, standing opposite the Sun and near the central bulge of the Milky Way rising above the eastern (top) horizon. The Large and Small Magellanic clouds both shine through the airglow to the lower left of the galactic plane, toward the southern horizon.

Thumbnail image of picture found for this day. APOD: 2018 April 27 - Gaia's Milky Way
Explanation: This grand allsky view of our Milky Way and nearby galaxies is not a photograph. It's a map based on individual measurements for nearly 1.7 billion stars. The astronomically rich data set used to create it, the sky-scanning Gaia satellite's second data release, includes remarkably precise determinations of position, brightness, colour, and parallax distance for 1.3 billion stars. Of course, that's about 1 percent of the total number of stars in the Milky Way. The flat plane of our galaxy still dominates the view. Home to most Milky Way stars it stretches across the center of Gaia's stellar data map. Voids and rifts along the galactic plane correspond to starlight-obscuring interstellar dust clouds. At lower right are stars of the Large and Small Magellanic Clouds, neighboring galaxies that lie just beyond the Milky Way.

Thumbnail image of picture found for this day. APOD: 2018 April 18 - Milky Way over Deadvlei in Namibia
Explanation: What planet is this? It is the only planet currently known to have trees. The trees in Deadvlei, though, have been dead for over 500 years. Located in Namib-Naukluft Park in Namibia (Earth), saplings grew after rainfall caused a local river to overflow, but died after sand dunes shifted to section off the river. High above and far in the distance, the band of our Milky Way Galaxy forms an arch over a large stalk in this well-timed composite image, taken last month. The soil of white clay appears to glow by reflected starlight. Rising on the left, under the Milky Way's arch, is a band of zodiacal light -- sunlight reflected by dust orbiting in the inner Solar System. On the right, just above one of Earth's larger sand dunes, an astute eye can find the Large Magellanic Cloud, a satellite galaxy of our galaxy. Finding the Small Magellanic Cloud in the featured image, though, is perhaps too hard.

Thumbnail image of picture found for this day. APOD: 2018 April 3 - The Milky Way over the Seven Strong Men Rock Formations
Explanation: You may have heard of the Seven Sisters in the sky, but have you heard about the Seven Strong Men on the ground? Located just west of the Ural Mountains, the unusual Manpupuner rock formations are one of the Seven Wonders of Russia. How these ancient 40-meter high pillars formed is yet unknown. The persistent photographer of this featured image battled rough terrain and uncooperative weather to capture these rugged stone towers in winter at night, being finally successful in February of 2014. Utilizing the camera's time delay feature, the photographer holds a flashlight in the foreground near one of the snow-covered pillars. High above, millions of stars shine down, while the band of our Milky Way Galaxy crosses diagonally down from the upper left.

Thumbnail image of picture found for this day. APOD: 2018 March 6 - Colorful Airglow Bands Surround Milky Way
Explanation: Why would the sky glow like a giant repeating rainbow? Airglow. Now air glows all of the time, but it is usually hard to see. A disturbance however -- like an approaching storm -- may cause noticeable rippling in the Earth's atmosphere. These gravity waves are oscillations in air analogous to those created when a rock is thrown in calm water. Red airglow likely originates from OH molecules about 87-kilometers high, excited by ultraviolet light from the Sun, while orange and green airglow is likely caused by sodium and oxygen atoms slightly higher up. While driving near Keluke Lake in Qinghai Provence in China, the photographer originally noticed mainly the impressive central band of the Milky Way Galaxy. Stopping to photograph it, surprisingly, the resulting sensitive camera image showed airglow bands to be quite prominent and span the entire sky. The featured image has been digitally enhanced to make the colors more vibrant.

Thumbnail image of picture found for this day. APOD: 2018 January 5 - Carina over Lake Ballard
Explanation: A jewel of the southern sky, the Great Carina Nebula, also known as NGC 3372, is one of our galaxy's largest star forming regions. Easily visible to the unaided eye it stands high above the signature hill of Lake Ballard, ephemeral salt lake of Western Australia, in this serene night skyscape from December 25, 2017. The Milky Way itself stretches beyond the southern horizon. Along the Milky Way, bright stars Alpha and Beta Centauri lie just above the hill's right flank, with the Southern Cross and dark Coalsack Nebula above the hill top. Based on a 22 panel mosaic, the scene was cropped to reveal more closely the beauty of this region of the southern Milky Way. On that short summer night, a star tracking camera mount was used to record the mosaic images of the sky, but turned off to image the foreground in moonlight.

Thumbnail image of picture found for this day. APOD: 2017 December 21 - Solstice Sun and Milky Way
Explanation: Welcome to December's solstice, first day of winter in the north and summer for the southern hemisphere. Astronomical markers of the seasons, solstice and equinox dates are based on the Sun's place in its annual journey along the ecliptic, through planet Earth's sky. At this solstice, the Sun reaches its maximum southern declination of -23.5 degrees today at 16:28 UTC, while its right ascension coordinate on the celestial sphere is 18 hours. That puts the Sun in the constellation Sagittarius in a direction near the center of our Milky Way galaxy. In fact, if you could see today's Solstice Sun against faint background stars and nebulae (that's really hard to do, especially in the daytime ...) your view might look something like this composited panorama. To make it, images of our fair galaxy were taken under dark Namibian night skies, then stitched together in a panoramic view. From a snapshot made on December 21, 2015, the Sun was digitally overlayed as a brilliant star at today's northern winter solstice position, close to the center of the Milky Way.

Thumbnail image of picture found for this day. APOD: 2017 October 10 - Milky Way and Zodiacal Light over Australian Pinnacles
Explanation: What strange world is this? Earth. In the foreground of the featured image are the Pinnacles, unusual rock spires in Nambung National Park in Western Australia. Made of ancient sea shells (limestone), how these human-sized picturesque spires formed remains a topic of research. The panorama was taken last month. A ray of zodiacal light, sunlight reflected by dust grains orbiting between the planets in the Solar System, rises from the horizon near the image center. Arching across the top is the central band of our Milky Way Galaxy. The planets Jupiter and Saturn, as well as several famous stars are also visible in the background night sky.

Thumbnail image of picture found for this day. APOD: 2017 September 2 - Milky Way Voyager
Explanation: Launched in 1977 on a tour of the outer planets of the Solar System, Voyager 1 and 2 have become the longest operating and most distant spacecraft from Earth. Nearly 16 light-hours from the Sun, Voyager 2 has reached the edge of the heliosphere, the realm defined by the influence of the solar wind and the Sun's magnetic field. Now humanity's first ambassador to the Milky Way, Voyager 1 is over 19 light-hours away, beyond the heliosphere in interstellar space. Celebrate the Voyagers' 40 year journey toward the stars with NASA on September 5.

Thumbnail image of picture found for this day. APOD: 2017 August 21 - Milky Way over Chilean Volcanoes
Explanation: Sometimes, the sky mimics the ground. Taken in 2017 May from the Atacama Desert in Chile, the foreground of the featured image encompasses the dipping edge of the caldera of an extinct volcano. Poetically echoing the dip below is the arch of our Milky Way Galaxy above. Many famous icons dot this southern nighttime vista, including the center of our Milky Way Galaxy on the far left, the bright orange star Antares also on the left, the constellation of the Southern Cross near the top of the arch, and the red-glowing Gum Nebula on the far right. Just above the horizon and splitting two distant volcanic peaks near the image center is the Large Magellanic Cloud -- the largest satellite galaxy of the Milky Way.

Thumbnail image of picture found for this day. APOD: 2017 August 6 - Milky Way and Exploding Meteor
Explanation: Next weekend the Perseid Meteor Shower reaches its maximum. Grains of icy rock will streak across the sky as they evaporate during entry into Earth's atmosphere. These grains were shed from Comet Swift-Tuttle. The Perseids result from the annual crossing of the Earth through Comet Swift-Tuttle's orbit, and are typically the most active meteor shower of the year. Although it is hard to predict the level of activity in any meteor shower, in a clear dark sky an observer might see a meteor a minute. This year's Perseids peak nearly a week after full Moon, and so some faint meteors will be lost to the lunar skyglow. Meteor showers in general are best be seen from a relaxing position, away from lights. Featured here is a meteor caught exploding during the 2015 Perseids above Austria next to the central band of our Milky Way Galaxy.

Thumbnail image of picture found for this day. APOD: 2017 July 26 - The Milky Way over Monument Valley
Explanation: You don't have to be at Monument Valley to see the Milky Way arc across the sky like this -- but it helps. Only at Monument Valley USA would you see a picturesque foreground that includes these iconic rock peaks called buttes. Buttes are composed of hard rock left behind after water has eroded away the surrounding soft rock. In the featured image taken a month ago, the closest butte on the left and the butte to its right are known as the Mittens, while Merrick Butte can be seen farther to the right. Green airglow fans up from the horizon. High overhead stretches a band of diffuse light that is the central disk of our spiral Milky Way Galaxy. The band of the Milky Way can be spotted by almost anyone on almost any clear night when far enough from a city and surrounding bright lights, but a sensitive digital camera is needed to capture these colors in a dark night sky.

Thumbnail image of picture found for this day. APOD: 2017 June 10 - Saturn in the Milky Way
Explanation: Saturn is near opposition in planet Earth's sky. Rising at sunset and shining brightly throughout the night, it also lies near a line-of-sight to crowded starfields, nebulae, and obscuring dust clouds along the Milky Way. Whitish Saturn is up and left of center in this gorgeous central Milky Way skyscape, a two panel mosaic recorded earlier this month. You can find the bright planet above the bowl of the dusty Pipe nebula, and just beyond the end of a dark river to Antares, alpha star of the constellation Scorpius. For now the best views of the ringed giant planet are from the Saturn-orbiting Cassini spacecraft, though. Diving close, Cassini's Grand Finale orbit number 8 is in progress.

Thumbnail image of picture found for this day. APOD: 2017 March 28 - King of Wings Hoodoo under the Milky Way
Explanation: This rock structure is not only surreal -- it's real. The reason it's not more famous is that it is, perhaps, smaller than one might guess: the capstone rock overhangs only a few meters. Even so, the King of Wings outcrop, located in New Mexico, USA, is a fascinating example of an unusual type of rock structure called a hoodoo. Hoodoos may form when a layer of hard rock overlays a layer of eroding softer rock. Figuring out the details of incorporating this hoodoo into a night-sky photoshoot took over a year. Besides waiting for a suitably picturesque night behind a sky with few clouds, the foreground had to be artificially lit just right relative to the natural glow of the background. After much planning and waiting, the final shot, featured here, was taken in May 2016. Mimicking the horizontal bar, the background sky features the band of our Milky Way Galaxy stretching overhead.

Thumbnail image of picture found for this day. APOD: 2017 February 3 - Milky Way with Airglow Australis
Explanation: Captured last April after sunset on a Chilean autumn night an exceptionally intense airglow flooded this scene. The panoramic skyscape is also filled with stars, clusters, and nebulae along the southern Milky Way including the Large and Small Magellanic clouds. Originating at an altitude similar to aurorae, the luminous airglow is due to chemiluminescence, the production of light through chemical excitation. Commonly recorded with a greenish tinge by sensitive digital cameras, both red and green airglow emission here is predominately from atmospheric oxygen atoms at extremely low densities and has often been present in southern hemisphere nights during the last few years. Like the Milky Way on that dark night the strong airglow was visible to the eye, but seen without color. Mars, Saturn, and bright star Antares in Scorpius form the celestial triangle anchoring the scene on the left. The road leads toward the 2,600 meter high mountain Cerro Paranal and the European Southern Observatory's Very Large Telescopes.

Thumbnail image of picture found for this day. APOD: 2016 November 30 - Milky Way over Shipwreck
Explanation: What happened to this ship? It was carried aground by a giant storm that struck the coast of Argentina in 2002. The pictured abandoned boat, dubbed Naufragio del Chubasco, wrecked near the nearly abandoned town of Cabo Raso (population: 1). The rusting ship provides a picturesque but perhaps creepy foreground for the beautiful sky above. This sky is crowned by the grand arch of our Milky Way and features galaxies including the Large and Small Magellanic Clouds, stars including Canopus and Altair, planets including Mars and Neptune, and nebulas including the Lagoon, Carina, and the Coal Sack. The mosaic was composed from over 80 images taken in early September. A 360-degree interactive panoramic version of this image is also available. The adventurous astrophotographer reports that the creepiest part of taking this picture was not the abandoned ship, but the unusual prevalence of black and hairy caterpillars.

Thumbnail image of picture found for this day. APOD: 2016 November 10 - Great Rift Near the Center of the Milky Way
Explanation: Over 100 telescopic image panels in this stunning vertical mosaic span about 50 degrees across the night sky. They follow part of the Great Rift, the dark river of dust and molecular gas that stretches along the plane of our Milky Way Galaxy. Start at top center and you can follow the galactic equator down through brighter stars in constellations Aquila, Serpens Cauda, and Scutum. At the bottom is Sagittarius near the center of the Milky Way. Along the way you'll encounter many obscuring dark nebulae hundreds of light-years distant flanked by bands of Milky Way starlight, and the telltale reddish glow of starforming regions. Notable Messier objects include The Eagle (M16) and Omega (M17) nebulae, the Sagittarius Star Cloud (M24), the beautiful Trifid (M20) and the deep Lagoon (M8).

Thumbnail image of picture found for this day. APOD: 2016 August 26 - The Milky Way Sets
Explanation: Under dark skies the setting of the Milky Way can be a dramatic sight. Stretching nearly parallel to the horizon, this rich, edge-on vista of our galaxy above the dusty Namibian desert stretches from bright, southern Centaurus (left) to Cepheus in the north (right). From early August, the digitally stitched, panoramic night skyscape captures the Milky Way's congeries of stars and rivers of cosmic dust, along with colors of nebulae not readily seen with the eye. Mars, Saturn, and Antares, visible even in more luminous night skies, form the the bright celestial triangle just touching the trees below the galaxy's central bulge. Of course, our own galaxy is not the only galaxy in the scene. Two other major members of our local group, the Andromeda Galaxy and the Triangulum Galaxy, lie near the right edge of the frame, beyond the arc of the setting Milky Way.

Thumbnail image of picture found for this day. APOD: 2016 July 23 - Summer Planets and Milky Way
Explanation: Lights sprawl toward the horizon in this night skyscape from Uludag National Park, Bursa Province, Turkey, planet Earth. The stars and nebulae of the Milky Way are still visible though, stretching above the lights on the northern summer night while three other planets shine brightly. Jupiter is at the far right, Mars near the center of the frame, and Saturn is just right of the bulging center of our galaxy. Because the panoramic scene was captured on July 6, all three planets pictured were hosting orbiting, operational, robotic spacecraft from Earth. Popular Mars has five (from three different space agencies): MAVEN (NASA), Mars Orbiter Mission (India), Mars Express (ESA), Mars Odyssey (NASA), Mars Reconnaissance Orbiter (NASA). Ringed Saturn hosts the daring Cassini spacecraft. Just arrived, Juno now orbits ruling gas giant Jupiter.

Thumbnail image of picture found for this day. APOD: 2016 July 7 - The Altiplano Night
Explanation: The Milky Way is massively bright on this cold, clear, altiplano night. At 4,500 meters its reflection in a river, a volcanic peak on the distant horizon, is captured in this stitched panorama under naturally dark skies of the northern Chilean highlands near San Pedro de Atacama. Along the Solar System's ecliptic plane, the band of Zodiacal light also stands out, extending above the Milky Way toward the upper left. In the scene from late April, brilliant Mars, Saturn, and Antares form a bright celestial triangle where ecliptic meets the center of the Milky Way. Left of the triangle, the large purple-red emission nebula Sharpless 2-27, more than twenty Moon diameters wide is centered around star Zeta Ophiuchi.

Thumbnail image of picture found for this day. APOD: 2016 July 2 - Firefly Trails and the Summer Milky Way
Explanation: A camera fixed low to a tripod on a northern summer's eve captured the series of images used in this serene, southern Ontario skyscape. The lakeside view frames our fair galaxy above calm water and the night's quintessential luminous apparitions. But the trails of light are neither satellite glint, nor meteor flash, nor auroral glow. In the wide-field composite constructed with four consecutive 15 second exposures, a pulsing firefly enters at the right, first wandering toward the camera, then left and back toward the lake, the central Milky Way rising in the background.

Thumbnail image of picture found for this day. APOD: 2016 May 24 - Milky Way Over the Spanish Peaks
Explanation: That's not lightning, and it did not strike between those mountains. The diagonal band is actually the central band of our Milky Way Galaxy, while the twin peaks are actually called the Spanish Peaks -- but located in Colorado, USA. Although each Spanish peak is composed of a slightly different type of rock, both are approximately 25 million years old. This serene yet spirited image composite was meticulously created by merging a series of images all taken from the same location on one night and early last month. In the first series of exposures, the background sky was built up, with great detail being revealed in the Milky Way dust lanes as well as the large colorful region surrounding the star Rho Ophiuchus just right of center. One sky image, though, was taken using a fogging filter so that brighter stars would appear more spread out and so more prominent. As a bonus, the planets Mars and Saturn are placed right above peaks and make an orange triangle with the bright star Antares. Later that night, after the moonrise, the Moon itself naturally illuminated the snow covered mountain tops.

Thumbnail image of picture found for this day. APOD: 2016 May 21 - Milky Way and Planets Near Opposition
Explanation: In this early May night skyscape, a mountain road near Bursa, Turkey seems to lead toward bright planets Mars and Saturn and the center of our Milky Way Galaxy, a direction nearly opposite the Sun in planet Earth's sky. The brightest celestial beacon on the scene, Mars, reaches its opposition tonight and Saturn in early June. Both will remain nearly opposite the Sun, up all night and close to Earth for the coming weeks, so the time is right for good telescopic viewing. Mars and Saturn form the tight celestial triangle with red giant star Antares just right of the Milky Way's central bulge. But tonight the Moon is also at opposition. Easy to see near bright Mars and Saturn, the Full Moon's light will wash out the central Milky Way's fainter starlight though, even in dark mountain skies.

Thumbnail image of picture found for this day. APOD: 2016 May 15 - Milky Way Over Quiver Tree Forest
Explanation: In front of a famous background of stars and galaxies lies some of Earth's more unusual trees. Known as quiver trees, they are actually succulent aloe plants that can grow to tree-like proportions. The quiver tree name is derived from the historical usefulness of their hollowed branches as dart holders. Occurring primarily in southern Africa, the trees pictured in the above 16-exposure composite are in Quiver Tree Forest located in southern Namibia. Some of the tallest quiver trees in the park are estimated to be about 300 years old. Behind the trees is light from the small town of Keetmanshoop, Namibia. Far in the distance, arching across the background, is the majestic central band of our Milky Way Galaxy. Even further in the distance, visible on the image left, are the Large and Small Magellanic Clouds, smaller satellite galaxies of the Milky Way that are prominent in the skies of Earth's southern hemisphere.

Thumbnail image of picture found for this day. APOD: 2016 May 14 - Falcon 9 and Milky Way
Explanation: On May 6, the after midnight launch of a SpaceX Falcon 9 rocket lit up dark skies over Merritt Island, planet Earth. Its second stage bound for Earth orbit, the rocket's arc seems to be on course for the center of the Milky Way in this pleasing composite image looking toward the southeast. Two consecutive exposures made with camera fixed to a tripod were combined to follow rocket and home galaxy. A 3 minute long exposure at low sensitivity allowed the rocket's first stage burn to trace the bright orange arc and a 30 second exposure at high sensitivity captured the stars and the faint Milky Way. Bright orange Mars dominates the starry sky at the upper right. A few minutes later, booster engines were restarted and the Falcon 9's first stage headed for a landing on the autonomous spaceport drone ship Of Course I Still Love You, patiently waiting in the Atlantic 400 miles east of the Cape Canaveral launch site.

Thumbnail image of picture found for this day. APOD: 2016 May 10 - Saturn and Mars visit Milky Way Star Clouds
Explanation: Planets, stars, nebulas and a galaxy -- this impressive image has them all. Closest to home are the two planets Mars (right) and Saturn (center), visible as the two bright orange spots in the upper half of the featured image. On the central right are the colorful Rho Ophiuchus star clouds featuring the bright orange star Antares lined up below Mars. These interstellar clouds contain both red emission nebulas and blue reflection nebulas. At the top right of the image is the Blue Horsehead reflection nebula. On the lower left are many dark absorption nebulas that extend from the central band of our Milky Way Galaxy. The featured deep composite was composed of multiple deep exposures taken last month from Brazil. Although you need a telescope to see the nebulosities, Saturn and Mars will remain visible to the unaided eye this month toward the east, just after sunset.

Thumbnail image of picture found for this day. APOD: 2016 April 23 - Milky Way in Moonlight
Explanation: A waning crescent moon, early morning twilight, and Al Hamra's city lights on the horizon can't hide the central Milky Way in this skyscape from planet Earth. Captured in a single exposure, the dreamlike scene looks southward across the region's grand canyon from Jabal Shams (Sun Mountain), near the highest peak in Oman, on the Arabian Peninsula. Mist, moonlight, and shadows still play along the steep canyon walls. Dark rifts along the luminous band of the Milky Way are the galaxy's cosmic dust clouds. Typically hundreds of light-years distant, they obscure starlight along the galactic plane, viewed edge-on from the Solar System's perspective.

Thumbnail image of picture found for this day. APOD: 2016 March 25 - Close Comet and the Milky Way
Explanation: Comet 252P/Linear's lovely greenish coma is easy to spot in this expansive southern skyscape. Visible to the naked eye from the dark site near Flinders, Victoria, Australia, the comet appears tailless. Still, its surprisingly bright coma spans about 1 degree, posed here below the nebulae, stars, and dark rifts of the Milky Way. The five panels used in the wide-field mosaic were captured after moonset and before morning twilight on March 21. That was less than 24 hours from the comet's closest approach, a mere 5.3 million kilometers from our fair planet. Sweeping quickly across the sky because it is so close to Earth, the comet should be spotted in the coming days by northern hemisphere comet watchers. In predawn but moonlit skies it will move through Sagittarius and Scorpius seen toward the southern horizon. That's near the triangle formed by bright, yellowish, Mars, Saturn, and Antares at the upper left of this frame.

Thumbnail image of picture found for this day. APOD: 2016 February 17 - Milky Way over the Pinnacles in Australia
Explanation: What strange world is this? Earth. In the foreground of the featured image are the Pinnacles, unusual rock spires in Nambung National Park in Western Australia. Made of ancient sea shells (limestone), how these human-sized picturesque spires formed remains unknown. In the background, just past the end of the central Pinnacle, is a bright crescent Moon. The eerie glow around the Moon is mostly zodiacal light, sunlight reflected by dust grains orbiting between the planets in the Solar System. Arching across the top is the central band of our Milky Way Galaxy. Many famous stars and nebula are also visible in the background night sky. The featured 29-panel panorama was taken and composed last September after detailed planning that involved the Moon, the rock spires, and their corresponding shadows. Even so, the strong zodiacal light was a pleasant surprise.

Thumbnail image of picture found for this day. APOD: 2015 November 7 - Earth and Milky Way from Space
Explanation: Since November 2000, people have been living continuously on the International Space Station. To celebrate humanity's 15th anniversary off planet Earth, consider this snapshot from space of our galaxy and our home world posing together beyond the orbital outpost. The Milky Way stretches below the curve of Earth's limb in the scene that also records a faint red, extended airglow. The galaxy's central bulge appears with starfields cut by dark rifts of obscuring interstellar dust. The picture was taken by Astronaut Scott Kelly on August 9, 2015, the 135th day of his one-year mission in space.

Thumbnail image of picture found for this day. APOD: 2015 November 1 - The Milky Way Over Monument Valley
Explanation: You don't have to be at Monument Valley to see the Milky Way arch across the sky like this -- but it helps. Only at Monument Valley USA would you see a picturesque foreground that includes these iconic rock peaks called buttes. Buttes are composed of hard rock left behind after water has eroded away the surrounding soft rock. In the featured image taken in 2012, the closest butte on the left and the butte to its right are known as the Mittens, while Merrick Butte can be seen just further to the right. High overhead stretches a band of diffuse light that is the central disk of our spiral Milky Way Galaxy. The band of the Milky Way can be spotted by almost anyone on almost any clear night when far enough from a city and surrounding bright lights.

Thumbnail image of picture found for this day. APOD: 2015 September 22 - Milky Way over Bosque Alegre Station in Argentina
Explanation: What are those streaks of light in the sky? First and foremost, the arching structure is the central band of our Milky Way galaxy. Visible in this galactic band are millions of distant stars mixed with numerous lanes of dark dust. Harder to discern is a nearly vertical beam of light rising from the horizon, just to the right of the image center. This beam is zodiacal light, sunlight scattered by dust in our Solar System that may be surprisingly prominent just after sunset or just before sunrise. In the foreground are several telescopes of the Bosque Alegre Astrophysical Station of the National University of Cordoba in Argentina. The station schedules weekend tours and conducts research into the nature of many astronomical objects including comets, active galaxies, and clusters of galaxies. The featured image was taken early this month.

Thumbnail image of picture found for this day. APOD: 2015 September 4 - Milky Way with Airglow Australis
Explanation: After sunset on September 1, an exceptionally intense, reddish airglow flooded this Chilean winter night skyscape. Above a sea of clouds and flanking the celestial Milky Way, the airglow seems to ripple and flow across the northern horizon in atmospheric waves. Originating at an altitude similar to aurorae, the luminous airglow is instead due to chemiluminescence, the production of light through chemical excitation. Commonly captured with a greenish tinge by sensitive digital cameras, this reddish airglow emission is from OH molecules and oxygen atoms at extremely low densities and has often been present in southern hemisphere nights during the last few years. On this night it was visible to the eye, but seen without color. Antares and the central Milky Way lie near the top, with bright star Arcturus at left. Straddling the Milky Way close to the horizon are Vega, Deneb, and Altair, known in northern nights as the stars of the Summer Triangle.

Thumbnail image of picture found for this day. APOD: 2015 August 25 - Meteors and Milky Way over Mount Rainier
Explanation: Despite appearances, the sky is not falling. Two weeks ago, however, tiny bits of comet dust were. Featured here is the Perseids meteor shower as captured over Mt. Rainier, Washington, USA. The image was created from a two-hour time lapse video, snaring over 20 meteors, including one that brightened dramatically on the image left. Although each meteor train typically lasts less than a second, the camera was able to capture their color progressions as they disintegrated in the Earth's atmosphere. Here an initial green tint may be indicative of small amounts of glowing magnesium atoms that were knocked off the meteor by atoms in the Earth's atmosphere. To cap things off, the central band of our Milky Way Galaxy was simultaneously photographed rising straight up behind the snow-covered peak of Mt. Rainier. Another good meteor shower is expected in mid-November when debris from a different comet intersects Earth as the Leonids.

Thumbnail image of picture found for this day. APOD: 2015 August 13 - Moonless Meteors and the Milky Way
Explanation: Have you watched the Perseid meteor shower? Though the annual shower's predicted peak was last night, meteor activity should continue tonight (August 13/14), best enjoyed by just looking up in clear, dark skies after midnight. Of course, this year's Perseid shower has the advantage of being active near the August 14 New Moon. Since the nearly New Moon doesn't rise before the morning twilight many fainter meteors are easier to spot until then, with no interference from bright moonlight. The Perseid meteor shower last occurred near a New Moon in 2013. That's when the exposures used to construct this image were made, under dark, moonless skies from Hvar Island off the coast of Croatia. The widefield composite includes 67 meteors streaming from the heroic constellation Perseus, the shower's radiant, captured during 2013 August 8-14 against a background of faint zodiacal light and the Milky Way. The next moonless Perseid meteor shower will be in August 2018.

Thumbnail image of picture found for this day. APOD: 2015 August 12 - Milky Way and Exploding Meteor
Explanation: Tonight the Perseid Meteor Shower reaches its maximum. Grains of icy rock will streak across the sky as they evaporate during entry into Earth's atmosphere. These grains were shed from Comet Swift-Tuttle. The Perseids result from the annual crossing of the Earth through Comet Swift-Tuttle's orbit, and are typically the most active meteor shower of the year. Although it is hard to predict the level of activity in any meteor shower, in a clear dark sky an observer might see a meteor a minute. This year's Perseids occur just before a new Moon and so the relatively dark sky should make even faint meteors visible. Meteor showers in general are best be seen from a relaxing position, away from lights. Featured here is a meteor caught exploding two weeks ago above Austria next to the central band of our Milky Way Galaxy.

Thumbnail image of picture found for this day. APOD: 2015 July 30 - Milky Way over Uluru
Explanation: The central regions of our Milky Way Galaxy rise above Uluru/Ayers Rock in this striking night skyscape. Recorded on July 13, a faint airglow along the horizon shows off central Australia's most recognizable landform in silhouette. Of course the Milky Way's own cosmic dust clouds appear in silhouette too, dark rifts along the galaxy's faint congeries of stars. Above the central bulge, rivers of cosmic dust converge on a bright yellowish supergiant star Antares. Left of Antares, wandering Saturn shines in the night.

Thumbnail image of picture found for this day. APOD: 2015 July 27 - Milky Way and Aurora over Antarctica
Explanation: It has been one of the better skies of this long night. In parts of Antarctica, not only is it winter, but the Sun can spend weeks below the horizon. At China's Zhongshan Station, people sometimes venture out into the cold to photograph a spectacular night sky. The featured image from one such outing was taken in mid-July, just before the end of this polar night. Pointing up, the wide angle lens captured not only the ground at the bottom, but at the top as well. In the foreground is a colleague also taking pictures. In the distance, a spherical satellite receiver and several windmills are visible. Numerous stars dot the night sky, including Sirius and Canopus. Far in the background, stretching overhead from horizon to horizon, is the central band of our Milky Way Galaxy. Even further in the distance, visible as extended smudges near the top, are the Large and Small Magellanic Clouds, satellite galaxies near our huge Milky Way Galaxy.

Thumbnail image of picture found for this day. APOD: 2015 July 7 - The Milky Way from a Malibu Sea Cave
Explanation: What’s happening outside this cave? Nothing unexpected – it’s just the central band of our Milky Way Galaxy passing by. As the Earth turns, the band of our Galaxy appears to rotate and shift along the horizon. The featured image was taken by a photographer who professes a passion for locating sea caves, and who found this spectacular grotto in Leo Carrillo State Park near Malibu, California, USA. After some planning, he timed this single shot image through the 10-meter high cave entrance to show the Milky Way far in the distance. In the foreground, several rocks about one meter across are visible. Visible in the background starscape are millions of stars including the relatively bright and orange Antares, situated just to the right of the image center.

Thumbnail image of picture found for this day. APOD: 2015 June 8 - The Milky Way over the Temple of Poseidon
Explanation: What's that glowing in the distance? Although it may look like a lighthouse, the rays of light near the horizon actually emanate from the Temple of Poseidon at Cape Sounion, Greece. Some temple lights are even reflected in the Aegean Sea in the foreground. Although meant to be a monument to the sea, in this image, the temple's lights seem to be pointing out locations on the sky. For example, the wide ray toward the right fortuitously points toward the Lagoon Nebula in the central band of our Milky Way, which runs diagonally down the image from the upper left. Also, the nearly vertical beam seems to point toward the star clouds near the direction of the Wild Duck open cluster of stars. The featured image was taken less than three weeks ago.

Thumbnail image of picture found for this day. APOD: 2015 April 24 - Blue Tears and the Milky Way
Explanation: Lapping at rocks along the shore of the Island of Nangan, Taiwan, planet Earth, waves are infused with a subtle blue light in this sea and night skyscape. Composed of a series of long exposures made on April 16 the image captures the faint glow from Noctiluca scintillans. Also known as sea sparkles or blue tears, the marine plankton's bioluminescence is stimulated by wave motion. City lights along the coast of mainland China shine beneath low clouds in the west but stars and the faint Milky Way still fill the night above. Over the horizon the galaxy's central bulge and dark rifts seem to echo the rocks and luminous waves.

Thumbnail image of picture found for this day. APOD: 2015 April 23 - Meteor in the Milky Way
Explanation: Earth's April showers include the Lyrid Meteor Shower, observed for more than 2,000 years when the planet makes its annual passage through the dust stream of long-period Comet Thatcher. A grain of that comet's dust, moving 48 kilometers per second at an altitude of 100 kilometers or so, is swept up in this night sky view from the early hours of April 21. Flashing toward the southeastern horizon, the meteor's brilliant streak crosses the central region of the rising Milky Way. Its trail points back toward the shower's radiant in the constellation Lyra, high in the northern springtime sky and off the top of the frame. The yellowish hue of giant star Antares shines to the right of the Milky Way's bulge. Higher still is bright planet Saturn, near the right edge. Seen from Istra, Croatia, the Lyrid meteor's greenish glow reflects in the waters of the Adriatic Sea.

Thumbnail image of picture found for this day. APOD: 2015 April 13 - Milky Way over Erupting Volcano
Explanation: The view was worth the trip. Battling high winds, cold temperatures, and low oxygen, the trek to near the top of the volcano Santa Maria in Guatemala -- while carrying sensitive camera equipment -- was lonely and difficult. Once set up, though, the camera captured this breathtaking vista during the early morning hours of February 28. Visible on the ground are six volcanoes of the Central America Volcanic Arc, including Fuego, the Volcano of Fire, which is seen erupting in the distance. Visible in the sky, in separate exposures taken a few minutes later, are many stars much further in the distance, as well as the central band of our Milky Way Galaxy situated horizontally overhead.

Thumbnail image of picture found for this day. APOD: 2015 February 23 - The Milky Way Over the Arizona Toadstools
Explanation: Which is older -- the rocks you see on the ground or the light you see from the sky? Usually it’s the rocks that are older, with their origin sediments deposited well before light left any of the stars or nebulas you see in the sky. However, if you can see, through a telescope, a distant galaxy far across the universe -- further than Andromeda or spiral galaxy NGC 7331 (inset) -- then you are seeing light even more ancient. Featured here, the central disk of our Milky Way Galaxy arches over Toadstool hoodoos rock formations in northern Arizona, USA. The unusual Toadstool rock caps are relatively hard sandstone that wind has eroded more slowly than the softer sandstone underneath. The green bands are airglow, light emitted by the stimulated air in Earth's atmosphere. On the lower right is a time-lapse camera set up to capture the sky rotating behind the picturesque foreground scene.

Thumbnail image of picture found for this day. APOD: 2015 January 26 - The Milky Way over the Seven Strong Men Rock Formations
Explanation: You may have heard of the Seven Sisters in the sky, but have you heard about the Seven Strong Men on the ground? Located just west of the Ural Mountains, the unusual Manpupuner rock formations are one of the Seven Wonders of Russia. How these ancient 40-meter high pillars formed is yet unknown. The persistent photographer of this featured image battled rough terrain and uncooperative weather to capture these rugged stone towers in winter at night, being finally successful in February of last year. Utilizing the camera's time delay feature, the photographer holds a flashlight in the foreground near one of the snow-covered pillars. High above, millions of stars shine down, while the band of our Milky Way Galaxy crosses diagonally down from the upper left.

Thumbnail image of picture found for this day. APOD: 2014 December 5 - Milky Way over Moon Valley
Explanation: Our Milky Way Galaxy arcs over a desolate landscape in this fantastic panoramic night skyview. The otherworldly scene looks across the arid, eroded terrain of the Valle de la Luna in the Chilean Atacama desert. Just along the horizon are lights from San Pedro, Chile, as well as the small villages of Socaire and Toconao, and a tortuous road from the city of Calama to San Pedro. Taken on October 18th, the five panel mosaic also features the four galaxies easily visible from our fair planet's dark sky regions. At the far left, satellite galaxies known as the Large and Small Magellanic Clouds are framed by their terrestrial namesakes. Much fainter and at the right, beyond the Milky Way's central bulge, is the Andromeda Galaxy. The most distant in view, Andromeda lies some 2.5 million light-years away.

Thumbnail image of picture found for this day. APOD: 2014 October 31 - Milky Way over Devils Tower
Explanation: A mysterious formation known as Devils Tower rises into the dark above northeastern Wyoming's prairie landscape in this 16 frame panoramic view. Seen against the night sky's thin, pale clouds and eerie green airglow, star clusters and nebulae of the Milky Way arc toward the galaxy's central realm at right. Of course the scene contains the Milky Way's own haunting and grisly visages of halloween, including ghosts, a flaming skull, a glowing eye and a witch's broom. To find them, slide your cursor over the picture or just follow this link, if you dare. And have a safe and Happy Halloween!

Thumbnail image of picture found for this day. APOD: 2014 October 3 - Aurora and Milky Way in a Little Sky
Explanation: Stepping stones seem to lead to the Milky Way as it stretches across this little sky. Of course, the scene is really the northern hemisphere's autumnal equinox night. Water and sky are inverted by a top to bottom, around the horizon stereographic projection centered on the zenith above Lake Storsjön in Jämtland, Sweden. In the north the Milky Way arcs from east to west overhead as fall begins, but the season is also a good time for viewing aurora. Geomagnetic storms increase in frequency near the equinox and produce remarkable displays of northern lights at high latitudes, like the eerie greenish glow reflected in this watery cosmos.

Thumbnail image of picture found for this day. APOD: 2014 September 16 - Milky Way above Atacama Salt Lagoon
Explanation: Galaxies, stars, and a serene reflecting pool combine to create this memorable land and skyscape. The featured panorama is a 12-image mosaic taken last month from the Salar de Atacama salt flat in northern Chile. The calm water is Laguna Cejar, a salty lagoon featuring a large central sinkhole. On the image left, the astrophotographer's fiancee is seen capturing the same photogenic scene. The night sky is lit up with countless stars, the Large and Small Magellanic Cloud galaxies on the left, and the band of our Milky Way galaxy running diagonally up the right. The Milky Way may appear to be causing havoc at the horizon, but those are just the normal lights of a nearby town.

Thumbnail image of picture found for this day. APOD: 2014 September 9 - An Aurora Cupcake with a Milky Way Topping
Explanation: This sky looked delicious. Double auroral ovals were captured above the town lights of Östersund, Sweden, last week. Pictured above, the green ovals occurred lower to the ground than violet aurora rays above, making the whole display look a bit like a cupcake. To top it off, far in the distance, the central band or our Milky Way Galaxy slants down from the upper left. The auroras were caused by our Sun ejecting plasma clouds into the Solar System just a few days before, ionized particles that subsequently impacted the magnetosphere of the Earth. Aurora displays may continue this week as an active sunspot group rotated into view just a few days ago.

Thumbnail image of picture found for this day. APOD: 2014 August 27 - Milky Way over Yellowstone
Explanation: The Milky Way was not created by an evaporating lake. The colorful pool of water, about 10 meters across, is known as Silex Spring and is located in Yellowstone National Park in Wyoming, USA. Illuminated artificially, the colors are caused by layers of bacteria that grow in the hot spring. Steam rises off the spring, heated by a magma chamber deep underneath known as the Yellowstone hotspot. Unrelated and far in the distance, the central band of our Milky Way Galaxy arches high overhead, a band lit by billions of stars. The above picture is a 16-image panorama taken late last month. If the Yellowstone hotspot causes another supervolcanic eruption as it did 640,000 years ago, a large part of North America would be affected.

Thumbnail image of picture found for this day. APOD: 2014 July 24 - ALMA Milky Way
Explanation: This alluring all-skyscape was taken 5,100 meters above sea level, from the Chajnantor Plateau in the Chilean Andes. Viewed through the site's rarefied atmosphere at about 50% sea level pressure, the gorgeous Milky Way stretches through the scene. Its cosmic rifts of dust, stars, and nebulae are joined by Venus, a brilliant morning star immersed in a strong band of predawn Zodiacal light. Still not completely dark even at this high altitude, the night sky's greenish cast is due to airglow emission from oxygen atoms. Around the horizon the dish antenna units of the Atacama Large Millimeter/submillimeter Array, ALMA, explore the universe at wavelengths over 1,000 times longer than visible light.

Thumbnail image of picture found for this day. APOD: 2014 June 14 - New York to London Milky Way
Explanation: Bright stars of Sagittarius and the center of our Milky Way Galaxy lie just off the wing of a Boeing 747 in this astronomical travel photo. The stratospheric scene was captured earlier this month during a flight from New York to London, 11,000 meters above the Atlantic Ocean. Of course the sky was clear and dark at that altitude, ideal conditions for astronomical imaging. But there were challenges to overcome while looking out a passenger window of the aircraft moving at nearly 1,000 kilometers per hour (600 mph). Over 90 exposures of 30 seconds or less were attempted with a fast lens and sensitive camera setting, using a small, flexible tripod and a blanket to block reflections of interior lighting. In the end, one 10 second long exposure resulted in this steady and colorful example of airborne astronomy.

Thumbnail image of picture found for this day. APOD: 2014 May 9 - Halley Dust and Milky Way
Explanation: The early morning hours of May 6 were moonless when grains of cosmic dust streaked through dark skies. Swept up as planet Earth plows through dusty debris streams left behind periodic Comet Halley, the annual meteor shower is known as the Eta Aquarids. This inspired exposure captures a meteor streak moving left to right through the frame. Its trail points back across the arc of the Milky Way to the shower's radiant above the local horizon in the constellation Aquarius. Known for speed Eta Aquarid meteors move fast, entering the atmosphere at about 66 kilometers per second. Still waters of the small pond near Albion, Maine, USA reflect the starry scene and the orange glow of nearby artificial lights scattered by a low cloud bank. Of course, northern hemisphere skygazers are expecting a new meteor shower on May 24, the Camelopardalids, caused by dust from periodic comet 209P/LINEAR.

Thumbnail image of picture found for this day. APOD: 2014 April 12 - Clouds and Crosses over Haleakala
Explanation: Aloha and welcome to a breathtaking skyscape. The dreamlike panoramic view from March 27 looks out over the 10,000 foot summit of Haleakala on Maui, Hawai'i. A cloud layer seeps over the volcanic caldera's edge with the Milky Way and starry night sky above. Head of the Northern Cross asterism, supergiant star Deneb lurks within the Milky Way's dust clouds and nebulae at the left. From there you can follow the arc of the Milky Way all the way to the stars of the more compact Southern Cross, just above the horizon at the far right. Bright Saturn is near the top right of the frame, with red giant Antares below it and left, closer to the Milky Way's central bulge. Need some help identifying the stars? Just slide your cursor over the picture, or download this labeled panorama. (Editor's Note: After some more help identifying the stars, the identification of Mars in the original posting was replaced with Saturn - updated April 15.)

Thumbnail image of picture found for this day. APOD: 2014 March 29 - A Milky Way Dawn
Explanation: As dawn broke on March 27, the center of the Milky Way Galaxy stood almost directly above the European Southern Observatory's Paranal Observatory. In the dry, clear sky of Chile's Atacama desert, our galaxy's dusty central bulge is flanked by Paranal's four 8 meter Very Large Telescope units in this astronomical fisheye view. Along the top, Venus is close to the eastern horizon. The brilliant morning star shines very near a waning crescent Moon just at the edge of one of the telescope structures. Despite the bright pairing in the east, the Milky Way dominates the scene though. Cut by dust lanes and charged with clouds of stars and glowing nebulae, the center of our galaxy sprawls across the darker zenith even as the deep blue sky grows brighter and buildings still glint in moonlight.

Thumbnail image of picture found for this day. APOD: 2014 February 12 - Rocket, Meteor, and Milky Way over Thailand
Explanation: Can the night sky appear both serene and surreal? Perhaps classifiable as serene in the above panoramic image taken last Friday are the faint lights of small towns glowing across a dark foreground landscape of Doi Inthanon National Park in Thailand, as well as the numerous stars glowing across a dark background starscape. Also visible are the planet Venus and a band of zodiacal light on the image left. Unusual events are also captured, however. First, the central band of our Milky Way Galaxy, while usually a common sight, appears here to hover surreally above the ground. Next, a fortuitous streak of a meteor was captured on the image right. Perhaps the most unusual component is the bright spot just to the left of the meteor. That spot is the plume of a rising Ariane 5 rocket, launched a few minutes before from Kourou, French Guiana. How lucky was the astrophotographer to capture the rocket launch in his image? Pretty lucky -- the image was not timed to capture the rocket. Also lucky was how photogenic -- and perhaps surreal -- the rest of the sky turned out to be.

Thumbnail image of picture found for this day. APOD: 2013 September 6 - The Quiet Sagittarius A*
Explanation: Hot gas is hard to swallow. At least that seems to be true for the supermassive black hole at the center of our Milky Way Galaxy. Known as source Sagittarius A*, the Milky Way's black hole is centered in this infrared (red and yellow hues) and X-ray (blue) composite. Based on data from an extensive campaign of observations by the orbiting Chandra X-ray telescope, the diffuse emission surrounding the black hole is seen in the close-up inset, the inset field spanning about 1/2 light-year across the galactic center some 26,000 light-years away. Astronomers have found that the X-ray emission originates in hot gas drawn from the winds of massive young stars in the region. The Chandra data indicate that only about 1% or less of the gas within the black hole's gravitational influence ever reaches the event horizon, losing enough heat and angular momentum to fall into the black hole, while the rest of the gas escapes in an outflow. The result explains why the Milky Way's black hole is so quiet, much fainter than might be expected in energetic X-rays. It likely holds for most supermassive black holes in galaxies in the nearby Universe.

Thumbnail image of picture found for this day. APOD: 2013 September 2 - Milky Way Over Spain's Bardenas Reales
Explanation: What's that below the Milky Way? First, across the top of the above image, lies the faint band that is our planet's sideways view of the central disk of our home Milky Way Galaxy. The Milky Way band can be seen most clear nights from just about anywhere on Earth with a dark sky. What lies beneath is, by comparison, is a much less common sight. It is the striking peak of Castildetierra, a rock formation located in Bardenas Reales, a natural badlands in northeast Spain. Standing 50 meters tall, the rock spire includes clay and sandstone left over from thousands of years of erosion by wind and water. The astrophotographer waited months for the sky to appear just right -- and then took the 14 exposures that compose the above image in a single night.

Thumbnail image of picture found for this day. APOD: 2013 June 19 - Milky Way Over Crater Lake with Airglow
Explanation: How many different astronomical phenomena have come together to create the above vista? Several. First, in the foreground, is Crater Lake -- a caldera created by volcanism on planet Earth about 7,700 years ago. Next, inside the lake, is water. Although the origin of the water in the crater is melted snowfall, the origin of water on Earth more generally is unclear, but possibly related to ancient Earthly-impacts of icy bodies. Next, the green glow in the sky is airglow, light emitted by atoms high in the Earth's atmosphere as they recombine at night after being separated during the day by energetic sunlight. The many points of light in the sky are stars, glowing by nuclear fusion. They are far above the atmosphere but nearby to our Sun in the Milky Way Galaxy. Finally, the bright arch across the image is the central band of the Milky Way, much further away, on the average, than the nearby stars, and shaped mostly by gravity. Contrary to appearances, the Milky Way band glows by itself and is not illuminated by the airglow. The above image is a six-frame panorama taken during about two weeks ago in Oregon, USA.

Thumbnail image of picture found for this day. APOD: 2013 June 1 - The Milky Trail
Explanation: Have you ever hiked the Queen's Garden trail in Bryce Canyon, Utah, USA, planet Earth? Walking along that path in this dark night skyscape, you can almost imagine your journey continues along the pale, luminous Milky Way. Of course, the name for our galaxy, the Milky Way (in Latin, Via Lactea), does refer to its appearance as a milky band or path in the sky. In fact, the word galaxy itself derives from the Greek for milk. Visible on moonless nights from dark sky areas, though not so bright or quite so colorful as in this image, the glowing celestial band is due to the collective light of myriad stars along the plane of our galaxy, too faint to be distinguished individually. The diffuse starlight is cut by dark swaths of obscuring galactic dust clouds. Four hundred years ago, Galileo turned his telescope on the Milky Way and announced it to be "... a congeries of innumerable stars ..."

Thumbnail image of picture found for this day. APOD: 2013 April 29 - Milky Way and Stone Tree
Explanation: What's that next to the Milky Way? An unusual natural rock formation known as Roque Cinchado or Stone Tree found on the Spanish Canary Island of Tenerife. A famous icon, Roque Cinchado is likely a dense plug of cooled volcanic magma that remains after softer surrounding rock eroded away. Majestically, the central band of our Milky Way Galaxy is visible arcing across the right of the above seven image panoramic mosaic taken during the summer of 2010. On the far right is the Teide volcano complete with a lenticular cloud hovering near its peak.  

Thumbnail image of picture found for this day. APOD: 2013 April 20 - Airglow, Gegenschein, and Milky Way
Explanation: As far as the eye could see, it was a dark night at Las Campanas Observatory in the southern Atacama desert of Chile. But near local midnight on April 11, this mosaic of 3 minute long exposures revealed a green, unusually intense, atmospheric airglow stretching over thin clouds. Unlike aurorae powered by collisions with energetic charged particles and seen at high latitudes, the airglow is due to chemiluminescence, the production of light in a chemical reaction, and found around the globe. The chemical energy is provided by the Sun's extreme ultraviolet radiation. Like aurorae, the greenish hue of this airglow does originate at altitudes of 100 kilometers or so dominated by emission from excited oxygen atoms. The gegenschein, sunlight reflected by dust along the solar system's ecliptic plane was still visible on that night, a faint bluish cloud just right of picture center. At the far right, the Milky Way seems to rise from the mountain top perch of the Magellan telescopes. Left are the OGLE project and du Pont telescope domes.

Thumbnail image of picture found for this day. APOD: 2013 March 10 - Milky Way Panorama from Mauna Kea
Explanation: Aloha and welcome to a breathtaking skyscape. The dreamlike panoramic view looks out from the 4,200 meter volcanic summit of Mauna Kea, Hawai'i, across a layer of clouds toward a starry night sky and the rising Milky Way. Anchoring the scene on the far left is the dome of the Canada-France-Hawaii Telescope (CFHT), with north star Polaris shining beyond the dome to the right. Farther right, headed by bright star Deneb, the Northern Cross asterism is embedded along the plane of the Milky Way as it peeks above the horizon. Both Northern Cross and brilliant white Vega hang over a foreground grouping of cinder cones. Near the center are the reddish nebulae, stars and dust clouds of the central Milky Way. Below, illumination from the city lights of Hilo creates an eerie, greenish glow in the clouds. Red supergiant star Antares shines above the Milky Way's central bulge while bright Alpha Centauri lies still farther right, along the dusty galactic plane. Finally, at the far right is the large Gemini North Observatory. The compact group of stars known as the Southern Cross is just left of the telescope dome. Need some help identifying the stars? Just slide your cursor over the picture, or download this smaller, labeled panorama.

Thumbnail image of picture found for this day. APOD: 2013 January 24 - ISS and the Summer Milky Way
Explanation: Clouds on a summer night frame this sea and skyscape, recorded earlier this month near Buenos Aires, Argentina. But planet Earth's clouds are not the only clouds on the scene. Starry clouds and nebulae along the southern hemisphere's summer Milky Way arc above the horizon, including the dark Coal Sack near the Southern Cross and the tantalizing pinkish glow of the Carina Nebula. Both the Large (top center) and Small Magellanic Clouds are also in view, small galaxies in their own right and satellites of the Milky Way up to 200,000 light-years distant. Alpha star of the Carina constellation and second brightest star in Earth's night, Canopus shines above about 300 light-years away. Still glinting in sunlight at an altitude of 400 kilometers, the orbiting International Space Station traces a long streak through the single, 5 minute, star-tracking exposure.

Thumbnail image of picture found for this day. APOD: 2012 December 12 - Milky Way Over Quiver Tree Forest
Explanation: In front of a famous background of stars and galaxies lies some of Earth's more unusual trees. Known as quiver trees, they are actually succulent aloe plants that can grow to tree-like proportions. The quiver tree name is derived from the historical usefulness of their hollowed branches as dart holders. Occurring primarily in southern Africa, the trees pictured in the above 16-exposure composite are in Quiver Tree Forest located in southern Namibia. Some of the tallest quiver trees in the park are estimated to be about 300 years old. Behind the trees is light from the small town of Keetmanshoop, Namibia. Far in the distance, arching across the background, is the majestic central band of our Milky Way Galaxy. Even further in the distance, visible on the image left, are the Large and Small Magellanic Clouds, smaller satellite galaxies of the Milky Way that are prominent in the skies of Earth's southern hemisphere.

Thumbnail image of picture found for this day. APOD: 2012 November 2 - The Black Hole in the Milky Way
Explanation: At the center of our Milky Way Galaxy, a mere 27,000 light-years away, lies a black hole with 4 million times the mass of the Sun. Fondly known as Sagittarius A* (pronounced A-star), the Milky Way's black hole is fortunately mild-mannered compared to the central black holes in distant active galaxies, much more calmly consuming material around it. From time to time it does flare-up, though. An outburst lasting several hours is captured in this series of premier X-ray images from the orbiting Nuclear Spectroscopic Telescope Array (NuSTAR). Launched last June 13, NuSTAR is the first to provide focused views of the area surrounding Sgr A* at X-ray energies higher than those accessible to Chandra and XMM observatories. Spanning two days of NuSTAR observations, the flare sequence is illustrated in the panels at the far right. X-rays are generated in material heated to over 100 million degrees Celsius, accelerated to nearly the speed of light as it falls into the Miky Way's central black hole. The main inset X-ray image spans about 100 light-years. In it, the bright white region represents the hottest material closest to the black hole, while the pinkish cloud likely belongs to a nearby supernova remnant.

Thumbnail image of picture found for this day. APOD: 2012 October 20 - Zodiacal Light and Milky Way
Explanation: Ghostly apparitions of two fundamental planes in planet Earth's sky span this October all-sky view. The scene was captured from a lakeside campsite under dark skies in northern Maine, USA. In it, the plane of our Milky Way Galaxy arcs above faint airglow along the horizon. Zodiacal light, a band of dust scattering sunlight along the solar system's ecliptic plane, stretches almost horizontally across the wide field and intersects the Milky way near a point marked by bright planet Jupiter. Right of Jupiter, past the Pleiades star cluster, is the brightening of the Zodiacal band known as the Gegenschein, also visible to the eye on that dark night. Begirt with many a blazing star and rising above the distant mountains, Orion the hunter is reflected in the lake's calm waters.

Thumbnail image of picture found for this day. APOD: 2012 October 13 - Galaxies, Stars, and Dust
Explanation: Spiky stars and spooky shapes abound in this deep cosmic skyscape. Its well-composed field of view covers about 2 Full Moons on the sky toward the constellation Pegasus. Of course the brighter stars show diffraction spikes, the commonly seen effect of internal supports in reflecting telescopes, and lie well within our own Milky Way galaxy. The faint but pervasive clouds of interstellar dust ride above the galactic plane and dimly reflect the Milky Way's combined starlight. Known as high latitude cirrus or integrated flux nebulae they are associated with molecular clouds. In this case, the diffuse cloud cataloged as MBM 54, less than a thousand light-years distant, fills the scene. Other galaxies far beyond the Milky Way are visible through the ghostly apparitions, including the striking spiral galaxy NGC 7497 some 60 million light-years away. Seen almost edge-on near the center of the field, NGC 7497's own spiral arms and dust lanes echo the colors of the Milky Way's stars and dust.

Thumbnail image of picture found for this day. APOD: 2012 September 11 - Milky Way Over the Bungle Bungles
Explanation: Which part of this picture do you find more interesting -- the land or the sky? Advocates for the land might cite the beauty of the ancient domes of the Bungle Bungle Range in Western Australia. These picturesque domes appear as huge layered beehives and are made of sandstones and conglomerates deposited over 350 million years ago. Advocates for the sky might laud the beauty of the Milky Way's central band shown arching from horizon to horizon. The photogenic Milky Way band formed over 10 billion years ago and now includes many well-known nebulae and bright stars. Fortunately, you don't have to decide and can enjoy both together in this beautiful 8-frame panorama taken from the dark skies of Purnululu National Park about two months ago.

Thumbnail image of picture found for this day. APOD: 2012 August 14 - Perseid Meteors and the Milky Way
Explanation: Where will the next Perseid meteor appear? Sky enthusiasts who trekked outside for the Perseid meteor shower that peaked over the past few days typically had this question on their mind. Six meteors from this past weekend are visible in the above stacked image composite, including one bright fireball streaking along the band of the background Milky Way Galaxy. All Perseid meteors appear to come from the shower radiant in the constellation of Perseus. Early reports about this year's Perseids indicate that as many as 100 meteors per hour were visible from some dark locations during the peak. The above digital mosaic was taken near Weikersheim, Germany.

Thumbnail image of picture found for this day. APOD: 2012 August 1 - The Milky Way Over Monument Valley
Explanation: You don't have to be at Monument Valley to see the Milky Way arch across the sky like this -- but it helps. Only at Monument Valley USA would you see a picturesque foreground that includes these iconic rock peaks called buttes. Buttes are composed of hard rock left behind after water has eroded away the surrounding soft rock. In the above image taken about two months ago, the closest butte on the left and the butte to its right are known as the Mittens, while Merrick Butte can be seen just further to the right. High overhead stretches a band of diffuse light that is the central disk of our spiral Milky Way Galaxy. The band of the Milky Way can be spotted by almost anyone on almost any clear night when far enough from a city and surrounding bright lights.

Thumbnail image of picture found for this day. APOD: 2012 June 25 - Milky Way Over Piton de lEau
Explanation: Sometimes, if you wait long enough for a clear and moonless night, the stars will come out with a vengeance. One such occasion occurred earlier this month at the Piton de l'Eau on Reunion Island. In the foreground, surrounded by bushes and trees, lies a water filled volcanic crater serenely reflecting starlight. A careful inspection near the image center will locate Piton des Neiges, the highest peak on the island, situated several kilometers away. In the background, high above the lake, shines the light of hundreds of stars, most of which are within 100 light years, right in our stellar neighborhood. Far in the distance, arching majestically overhead, is the central band of our home Milky Way Galaxy, shining by the light of millions of stars each located typically thousands of light years away. The astrophotographer reports waiting for nearly two years for the sky and clouds to be just right to get the above shot.

Thumbnail image of picture found for this day. APOD: 2012 June 18 - Milky Way Above Easter Island
Explanation: Why were the statues on Easter Island built? No one is sure. What is sure is that over 800 large stone statues exist there. The Easter Island statues, stand, on the average, over twice as tall as a person and have over 200 times as much mass. Few specifics are known about the history or meaning of the unusual statues, but many believe that they were created about 500 years ago in the images of local leaders of a lost civilization. Pictured above, some of the stone giants were illuminated in 2009 under the central band of our Milky Way Galaxy.

Thumbnail image of picture found for this day. APOD: 2012 June 4 - Milky Way Galaxy Doomed: Collision with Andromeda Pending
Explanation: Will our Milky Way Galaxy collide one day with its larger neighbor, the Andromeda Galaxy? Most likely, yes. Careful plotting of slight displacements of M31's stars relative to background galaxies on recent Hubble Space Telescope images indicate that the center of M31 could be on a direct collision course with the center of our home galaxy. Still, the errors in sideways velocity appear sufficiently large to admit a good chance that the central parts of the two galaxies will miss, slightly, but will become close enough for their outer halos to become gravitationally entangled. Once that happens, the two galaxies will become bound, dance around, and eventually merge to become one large elliptical galaxy -- over the next few billion years. Pictured above is an artist's illustration of the sky of a world in the distant future when the central parts of each galaxy begin to destroy each other. The exact future of our Milky Way and the entire surrounding Local Group of Galaxies is likely to remain an active topic of research for years to come.

Thumbnail image of picture found for this day. APOD: 2012 March 29 - Rocket Trails in the Milky Way
Explanation: On March 27, five sounding rockets leapt into early morning skies from NASA's Wallops Flight Facility in Virginia. Part of the Anomalous Transport Rocket EXperiment (ATREX), begining at 4:58 am EDT the rockets launched consecutively at 80 second intervals. Releasing a chemical tracer they created luminous white clouds within Earth's ionosphere at altitudes above 60 to 65 miles, swept along by the poorly understood high-altitude jet stream. (Not the same jet stream that airliners fly through at altitudes of 5 to 6 miles.) Seen along the mid-atlantic region of the United States, the clouds drifted through starry skies, captured in this clear photograph from East Point, New Jersey. Looking south toward the launch site, the tantalizing celestial background includes the stars of Sagittarius, Scorpius, and the more permanent faint, white, luminous clouds of the Milky Way.

Thumbnail image of picture found for this day. APOD: 2011 September 24 - Mangaia's Milky Way
Explanation: From Sagittarius to Carina, the Milky Way Galaxy shines in this dark night sky above planet Earth's lush island paradise of Mangaia. Familiar to denizens of the southern hemisphere, the gorgeous skyscape includes the bulging galactic center at the upper left and bright stars Alpha and Beta Centauri just right of center. About 10 kilometers wide, volcanic Mangaia is the southernmost of the Cook Islands. Geologists estimate that at 18 million years old it is the oldest island in the Pacific Ocean. Of course, the Milky Way is somewhat older, with the galaxy's oldest stars estimated to be over 13 billion years old. (Editor's note: This image holds the distinction of being selected as winner in the Royal Observatory, Greenwich, Astronomy Photographer of the Year competition in the Earth and Space category.)

Thumbnail image of picture found for this day. APOD: 2011 September 2 - Herschel Views the Milky Way
Explanation: With a 3.5 meter diameter mirror, larger than the Hubble Space Telescope, ESA's Herschel Space Observatory explores the Universe at infrared wavelengths. Herschel is named for German-born British astronomer Frederick William Herschel who discovered infrared light over 200 years ago. Herschel's sensitive cameras have combined to deliver this spectacular skyscape looking toward the constellation of the Southern Cross. Spanning some 2 degrees the premier, false-color, far-infrared view captures our galaxy's cold dust clouds in extreme detail, showing a remarkable, connected maze of filaments and star-forming regions. Such observations are intended to unravel mysteries of star formation by surveying broad areas of the galactic plane.

Thumbnail image of picture found for this day. APOD: 2011 July 25 - Milky Way Over Abandoned Kilns
Explanation: What's that below the Milky Way? Historic kilns. Built in the 1870s in rural Nevada, USA to process local wood into charcoal, the kilns were soon abandoned due to a town fire and flooding, but remain in good condition even today. The above panorama is a digital conglomerate of five separate images taken in early June from the same location. Visible above the unusual kilns is a colorful star field, highlighted by the central band of our Milky Way Galaxy appearing along a diagonal toward the lower right. Many famous sites in our Galaxy are visible, including the Pipe Nebula and the Dark River to Antares, seen to the right of the Milky Way. The origin of the green mist on the lower left, however, is currently unexplained.

Thumbnail image of picture found for this day. APOD: 2011 July 10 - A Milky Way Band
Explanation: Most bright stars in our Milky Way Galaxy reside in a disk. Since our Sun also resides in this disk, these stars appear to us as a diffuse band that circles the sky. The above panorama of a northern band of the Milky Way's disk covers 90 degrees and is a digitally created mosaic of several independent exposures. Scrolling right will display the rest of this spectacular picture. Visible are many bright stars, dark dust lanes, red emission nebulae, blue reflection nebulae, and clusters of stars. In addition to all this matter that we can see, astronomers suspect there exists even more dark matter that we cannot see.

Thumbnail image of picture found for this day. APOD: 2011 June 17 - Eclipsed Moon in the Milky Way
Explanation: On June 15, the totally eclipsed Moon was very dark, with the Moon itself positioned on the sky toward the center of our Milky Way Galaxy. This simple panorama captures totality from northern Iran in 8 consecutive exposures each 40 seconds long. In the evocative scene, the dark of the eclipsed Moon competes with the Milky Way's faint glow. The tantalizing red lunar disk lies just above the bowl of the dark Pipe Nebula, to the right of the glowing Lagoon and Trifid nebulae and the central Milky Way dust clouds. At the far right, the wide field is anchored by yellow Antares and the colorful clouds of Rho Ophiuchi. To identify other sights of the central Milky Way just slide your cursor over the image. The total phase of this first lunar eclipse of 2011 lasted an impressive 100 minutes. Parts of the eclipse were visible from most of planet Earth, with notable exceptions of North and Central America.

Thumbnail image of picture found for this day. APOD: 2011 April 5 - The Milky Way Over Tenerife
Explanation: Have you ever seen the band of our Milky Way Galaxy? Chances are you have never seen it like this -- nor could you. In a clear sky from a dark location at the right time, a faint band of light is visible across the sky. This band is the disk of our spiral galaxy. Since we are inside this disk, the band appears to encircle the Earth. The above spectacular picture of the Milky Way arch, however, goes where the unaided eye cannot. The image is actually a deep digital fusion of nine photos that create a panorama fully 360 across. Taken recently in Teide National Park in Tenerife, Canary Islands, Spain, the image includes the Teide volcano, visible near the image center, behind a volcanic landscape that includes many large rocks. Far behind these Earthly structures are many sky wonders that are visible to the unaided eye, such as the band of the Milky Way, the bright waxing Moon inside the arch, and the Pleiades open star cluster (can you find it?). The deep exposure also brings out many sky wonders normally beyond human perception, many of which are labelled on the annotated image version, including Barnard's Loop, visible above as the half red ring below the Milky Way band.

Thumbnail image of picture found for this day. APOD: 2011 February 21 - Milky Way Over Switzerland
Explanation: What's visible in the night sky during this time of year? To help illustrate the answer, a beautiful land, cloud, and skyscape was captured earlier this month over Neuchâtel, Switzerland. Visible in the foreground were the snow covered cliffs of the amphitheater shaped Creux du Van, as well as distant trees, and town-lit clouds. Visible in the night sky (at midnight) were galaxies including the long arch of the central band of our Milky Way Galaxy, the Andromeda galaxy (M31), and the Triangulum galaxy (M33). Star clusters visible included NGC 752, M34, M35, M41, the double cluster, and the Beehive (M44). Nebulas visible included the Orion Nebula (M42), NGC 7822, IC 1396, the Rosette Nebula, the Flaming Star Nebula, the California Nebula, the Heart and Soul Nebulas, and the Pacman Nebula. Rolling your cursor over the above image will bring up labels for all of these. But the above wide angle sky image captured even more sky wonders. What other nebulas can you find in the above image?

Thumbnail image of picture found for this day. APOD: 2010 November 10 - Huge Gamma Ray Bubbles Found Around Milky Way
Explanation: Did you know that our Milky Way Galaxy has huge bubbles emitting gamma rays from the direction of the galactic center? Neither did anybody. As the data from the Earth-orbiting Fermi satellite began accumulating over the past two years, however, a large and unusual feature toward our Galaxy's center became increasingly evident. The two bubbles are visible together as the red and white spotted oval surrounding the center of the above all sky image, released yesterday. The plane of our Galaxy runs horizontally across the image center. Assuming the bubbles emanate from our Galaxy's center, the scale of the bubbles is huge, rivaling the entire Galaxy in size, and spanning about 50,000 light years from top to bottom. Earlier indications of the bubbles have been found on existing all sky maps in the radio, microwave, and X-ray. The cause of the bubbles is presently unknown, but will likely be researched for years to come.

Thumbnail image of picture found for this day. APOD: 2010 November 1 - The Milky Way Over the Peak of the Furnace
Explanation: On Reunion Island, it is known simply as "The Volcano." To others, it is known as the Piton de la Fournaise, which is French for the Peak of the Furnace. It is one of the most active volcanoes in the world. The Volcano started a new eruption last month by spewing hot lava bombs as high as 10 meters into the air from several vents. Pictured above, the recent eruption was caught before a star filled southern sky, appearing somehow contained beneath the arching band of our Milky Way Galaxy. Also visible in the background sky is the Pleiades open star cluster, the constellation of Orion, the brightest star Sirius, and the neighboring Large and Small Magellanic Cloud galaxies. (Can you find them?) The Piton de la Fournaise erupted for months in 2006, and for days in 2007, 2008, and in January of 2010. Nobody knows how long the current eruption will last, or when The Volcano will erupt next.

Thumbnail image of picture found for this day. APOD: 2010 August 23 - A Milky Way Shadow at Loch Ard Gorge
Explanation: Have you ever seen the Milky Way's glow create shadows? To do so, conditions need to be just right. First and foremost, the sky must be relatively clear of clouds so that the long band of the Milky Way's central disk can be seen. The surroundings must be very near to completely dark, with no bright artificial lights visible anywhere. Next, the Moon cannot be anywhere above the horizon, or its glow will dominate the landscape. Last, the shadows can best be caught on long camera exposures. In the above image taken in Port Campbell National Park, Victoria, Australia, seven 15-second images of the ground and de-rotated sky were digitally added to bring up the needed light and detail. In the foreground lies Loch Ard Gorge, named after a ship that tragically ran aground in 1878. The two rocks pictured are the remnants of a collapsed arch and are named Tom and Eva after the only two people who survived that Loch Ard ship wreck. A close inspection of the water just before the rocks will show reflections and shadows in light thrown by our Milky Way galaxy. Low clouds are visible moving through the serene scene in this movie.

Thumbnail image of picture found for this day. APOD: 2010 July 27 - The Milky Way Over Bryce Canyon
Explanation: What are those strange rock structures? They are towers and walls of sedimentary rock that are particularly plentiful in Bryce Canyon in Utah, USA. The rock columns may rise higher than 50 meters and are called hoodoos. On the far left is Thor's Hammer, perhaps the most famous hoodoo. The tall rock columns were carved, most typically, when a unusually dense cap of rock provided a layer of protection to rock underneath from rain-based erosion. In the above panoramic picture taken earlier this month and compressed horizontally, the foreground rocks were momentarily illuminated by a roving spotlight. Visible in the background are a few water clouds a few kilometers away hovering over the nearby Earth. Visible well beyond that are thousands of individually discernible stars averaging a few hundred light years away in the nearby Milky Way Galaxy. Far in the distance lie billions of stars that are thousands of light years away and compose the faintly glowing arch that is the visible central band of the flat disk of our Milky Way. Over many years, wind and rain will eventually cause the tops of the hoodoos to topple, whereafter the underlying column will likely completely erode away.

Thumbnail image of picture found for this day. APOD: 2010 July 9 - Microwave Milky Way
Explanation: Seen from our edge-on perspective, the Milky Way Galaxy sprawls across the middle of this false-color, all sky view. The expansive microwave map is based on 1 year's worth of data from instruments onboard the sky-surveying Planck spacecraft. Remarkably, the bright stripe of gas and dust clouds along the galactic plane and the galaxy's enormous arcing structures seen at microwave energies are hundreds or thousands of light-years away, while the mottled regions at the top and bottom represent the Cosmic Microwave Background (CMB) radiation, some 13.7 billion light-years distant. Left over from the Big Bang, fluctuations in the CMB reflect the origins of structure in the evolving universe. Analyzing the microwave data, Planck scientists plan to separate the contributions of the Milky Way and CMB radiation. The work will ferret out the characteristics of the CMB across the entire sky and glean information about the make up of our Milky Way Galaxy.

Thumbnail image of picture found for this day. APOD: 2010 July 5 - The Milky Way Over Pulpit Rock
Explanation: Can a picture of the sky be relaxing? A candidate for such a picture might be this image taken only last month from Cape Schank, Victoria, Australia. The frame is highlighted by a dreamlike lagoon, two galaxies, and tens of thousands of stars. The rock cropping on the left may appear from this angle like a human head, but the more famous rock structure is on the far right and known as Pulpit Rock. Across the top of the image runs a distant stream of bright stars and dark dust that is part of the disk of our spiral Milky Way Galaxy. On the right, just above Pulpit Rock, is the Milky Way's small neighboring galaxy the Small Magellanic Cloud (SMC). The bright white object just to the left of the SMC is a globular cluster of stars in the Milky Way known as 47 Tucana.

Thumbnail image of picture found for this day. APOD: 2010 May 19 - Milky Way Over Ancient Ghost Panel
Explanation: Long before Stonehenge was built, well before the Dead Sea Scrolls were written, ancient artists painted life-sized figures on canyon walls in Utah, USA -- but why? Nobody is sure. The entire panel of figures, which dates back about 7,000 years, is called the Great Gallery and was found on the walls of Horseshoe Canyon in Canyonlands National Park. The humans who painted them likely hunted Mammoths. The unusual fuzziness of largest figure led to this mural section's informal designation as the Holy Ghost Panel, although the intended attribution and societal importance of the figure are really unknown. The above image was taken during a clear night in March. The oldest objects in the above image are not the pictographs, however, but the stars of our Milky Way Galaxy far in the background, some of which are billions of years old.

Thumbnail image of picture found for this day. APOD: 2010 March 22 - The Nearby Milky Way in Cold Dust
Explanation: What shapes the remarkable dust tapestry of the nearby Milky Way Galaxy? No one knows for sure. The intricate structures, shown above, were resolved in new detail recently in a wide region of the sky imaged in far infrared light by the European Space Agency's Planck satellite. The above image is a digital fusion of three infrared colors: two taken at high resolution by Planck, while the other is an older image taken by the now defunct IRAS satellite. At these colors, the sky is dominated by the faint glow of very cold gas within only 500 light years of Earth. In the above image, red corresponds to temperatures as cold as 10 degrees Kelvin above absolute zero, while white corresponds to gas as warm at 40 Kelvins. The pink band across the lower part of the image is warm gas confined to the plane of our Galaxy. The bright regions typically hold dense molecular clouds that are slowly collapsing to form stars, whereas the dimmer regions are most usually diffuse interstellar gas and dust known as cirrus. Why these regions have intricate filamentary shapes shared on both large and small scales remains a topic of research. Future study of the origin and evolution of dust may help in the understanding the recent history of our Galaxy as well as how planetary systems such as our Solar System came to be born.

Thumbnail image of picture found for this day. APOD: 2010 March 20 - Zodiacal Light Vs. Milky Way
Explanation: Ghostly Zodiacal light, featured near the center of this remarkable panorama, is produced as sunlight is scattered by dust in the Solar System's ecliptic plane. In the weeks surrounding the March equinox (today at 1732 UT) Zodiacal light is more prominent after sunset in the northern hemisphere, and before sunrise in the south, when the ecliptic makes a steep angle with the horizon. In the picture, the narrow triangle of Zodiacal light extends above the western horizon and seems to end at the lovely Pleiades star cluster. Arcing above the Pleiades are stars and nebulae along the plane of our Milky Way Galaxy. Recorded on March 10 from Teide National Park on the island of Tenerife, the vista is composed of 4 separate pictures spanning over 180 degrees.

Thumbnail image of picture found for this day. APOD: 2009 November 25 - All Sky Milky Way Panorama
Explanation: If you could go far away from the Earth and look around the entire sky -- what would you see? Such was the goal of the All-Sky Milky Way Panorama 2.0 project of Axel Mellinger. Presented above is the result: a digital compilation of over 3,000 images comprising the highest resolution digital panorama of the entire night sky yet created. An interactive zoom version, featuring over 500 million pixels, can be found here. Every fixed astronomical object visible to the unaided eye has been imaged, including every constellation, every nebula, and every star cluster. Moreover, millions of individual stars are also visible, all in our Milky Way Galaxy, and many a thousand times fainter than a human can see. Dark filaments of dust lace the central band of our Milky Way Galaxy, visible across the image center. The satellite galaxies Large and Small Magellanic Clouds are visible on the lower right. This was not the first time Dr. Mellinger has embarked on such a project: the results of his first All-Sky Milky Way Panorama Project, taken using photographic film, are visible here.

Thumbnail image of picture found for this day. APOD: 2009 October 16 - Herschel Views the Milky Way
Explanation: With a 3.5 meter diameter mirror, larger than the Hubble Space Telescope, Herschel is ESA's new infrared observatory. The space-based telescope is named for German-born British astronomer Frederick William Herschel who discovered infrared light over 200 years ago. In initial tests, Herschel's cameras have combined to deliver this spectacular view along the plane of the Milky Way in the constellation of the Southern Cross. Spanning some 2 degrees the premier, false-color, far-infrared view captures our galaxy's cold dust clouds in extreme detail, showing a remarkable, connected maze of filaments and star-forming regions. These and planned future Herschel observations are intended to unravel mysteries of star formation by surveying broad areas of the galactic plane.

Thumbnail image of picture found for this day. APOD: 2009 September 26 - Gigagalaxy Zoom: Milky Way
Explanation: Our magnificent Milky Way Galaxy sprawls across this ambitious all-sky panorama. In fact, at 800 million pixels the full resolution mosaic strives to show all the stars the eye can see in planet Earth's night sky. Part of ESO's Gigagalaxy Zoom Project, the mosaicked images were recorded over several months of 2008 and 2009 at exceptional astronomical sites; the Atacama Desert in the southern hemisphere and the Canary Islands in the northern hemisphere. Also capturing bright planets and even a comet, the individual frames were stitched together and mapped into a single, flat, apparently seamless 360 by 180 degree view. The final result is oriented so the plane of our galaxy runs horizontally through the middle with the bulging Galactic Center at image center. Below and right of center are the Milky Way's satellite galaxies, the Magellanic Clouds.

Thumbnail image of picture found for this day. APOD: 2009 August 18 - The Milky Way Over the Badlands
Explanation: Why take a picture of just the Badlands when you can take one that also shows the spectacular sky above it? Just such a picture, actually a digital stitched panorama of four images, was taken in late June near midnight, looking southwest. In the foreground, the unusual buttes of the Badlands Wall, part of the Badlands National Park in South Dakota, USA, were momentarily illuminated by flashlight during a long duration exposure of the background night sky. The mountain-like buttes visible are composed of soft rock that show sharp erosion features from wind and water. The South Dakota Badlands also contain ancient beds rich with easy-to-find fossils. Some fossils are over 25 million years old and hold clues to the evolutionary origins of the horse and the saber-toothed tiger. Bright Jupiter dominates the sky on the left just above the buttes, while the spectacular Milky Way Galaxy runs down the image right.

Thumbnail image of picture found for this day. APOD: 2009 July 29 - The Milky Way Over Devils Tower
Explanation: Was Devils Tower once an explosive volcano? Famous for its appearance in films such as Close Encounters, the origin of Devil's Tower in Wyoming, USA is still debated, with a leading hypothesis holding that it is a hardened lava plume that probably never reached the surface to become a volcano. The lighter rock that once surrounded the dense volcanic neck has now eroded away, leaving the dramatic tower. High above, the central band of the Milky Way galaxy arches across the sky. Many notable sky objects are visible, including dark strands of the Pipe Nebula and the reddish Lagoon Nebula to the tower's right. Green grass and trees line the moonlit foreground, while clouds appear near the horizon to the tower's left. Unlike many other international landmarks, mountaineers are permitted to climb Devils Tower.

Thumbnail image of picture found for this day. APOD: 2009 June 13 - The Milky Road
Explanation: Inspired by the night skies of planet Earth in the International Year of Astronomy, photographer Larry Landolfi created this tantalizing fantasy view. The composited image suggests a luminous Milky Way is the heavenly extension of a country road. Of course, the name for our galaxy, the Milky Way (in Latin, Via Lactea), does refer to its appearance as a milky band or path in the sky. In fact, the word galaxy itself derives from the Greek for milk. Visible on moonless nights from dark sky areas, though not so bright or colorful as in this image, the glowing celestial band is due to the collective light of myriad stars along the plane of our galaxy, too faint to be distinguished individually. The diffuse starlight is cut by dark swaths of obscuring galactic dust clouds. Four hundred years ago, Galileo turned his telescope on the Milky Way and announced it to be "... a congeries of innumerable stars ..."

Thumbnail image of picture found for this day. APOD: 2009 May 19 - Sagittarius and the Central Milky Way
Explanation: What does the center of our Milky Way Galaxy look like? In visible light, no one knows! It is not possible to see the Galactic center in light our eyes are sensitive to because the thick dust in the plane of our Galaxy obscures it. If one looks in the direction of our Galaxy's center - which is toward the constellation of Sagittarius - many beautiful wonders become apparent, though. Large dust lanes and star clouds dominate the picture. As many as 30 Messier Objects are visible in the above spectacular image mosaic, including all types of nebulas and star clusters. Two notable nebula include the Lagoon Nebula (M8), a red patch just above and to the right of center, and slightly to its right is the red and blue Trifid Nebula (M20).

Thumbnail image of picture found for this day. APOD: 2009 May 1 - Lyrid Meteor and Milky Way
Explanation: On April 22nd, the Lyrid Meteor Shower visited planet Earth's sky, an annual shower produced as the Earth plows through dust from the tail of comet Thatcher. Usually Lyrid meteor watchers see only a drizzle. Just a few meteors per hour stream away from the shower's radiant point near bright star Vega in the constellation Lyra. But photographer Tony Rowell still managed to catch one bright Lyrid meteor. Recorded in early morning hours, his well-composed image looks toward the south from White Mountains of eastern California, USA. During the time exposure, he briefly illuminated an old mining cabin in the region's Ancient Bristlecone Pine Forest in the foreground. The rich starfields and dust clouds of our own Milky Way galaxy stretch across the background, along the meteor's glowing trail.

Thumbnail image of picture found for this day. APOD: 2009 February 19 - Mauna Kea Milky Way Panorama
Explanation: Aloha and welcome to a breathtaking skyscape. The dreamlike panoramic view looks out from the 4,200 meter volcanic summit of Mauna Kea, Hawai'i, across a layer of clouds toward a starry night sky and the rising Milky Way. Anchoring the scene on the far left is the dome of the Canada-France-Hawaii Telescope (CFHT), with north star Polaris shining beyond the dome to the right. Farther right, headed by bright star Deneb, the Northern Cross asterism is embedded along the plane of the Milky Way as it peeks above the horizon. Both Northern Cross and brilliant white Vega hang over a foreground grouping of cinder cones. Near the center are the reddish nebulae, stars and dust clouds of the central Milky Way. Below, illumination from the city lights of Hilo creates an eerie, greenish glow in the clouds. Red supergiant star Antares shines above the Milky Way's central bulge while bright Alpha Centauri lies still farther right, along the dusty galactic plane. Finally, at the far right is the large Gemini North Observatory. The compact group of stars known as the Southern Cross is just left of the telescope dome. Need some help identifying the stars? Just slide your cursor over the picture, or download this smaller, labeled panorama.

Thumbnail image of picture found for this day. APOD: 2009 February 12 - Zodiacal Light Vs. Milky Way
Explanation: Two fundamental planes of planet Earth's sky compete for attention in this remarkable wide-angle vista, recorded on January 23rd. Arcing above the horizon and into the night at the left is a beautiful band of Zodiacal Light - sunlight scattered by dust in the solar system's ecliptic plane. Its opponent on the right is composed of the faint stars, dust clouds, and nebulae along the plane of our Milky Way Galaxy. Both celestial bands stand above the domes and towers of the Teide Observatory on the island of Tenerife. Also out to play in the pristine, dark skies over the Canary Islands, are brilliant Venus (lower left), the distant Andromeda Galaxy (near center), and the lovely Pleiades star cluster (top center). Of course, seasoned skygazers might even spot M33, the California Nebula, IC1805, and the double star cluster of Perseus. (Need some help? Just slide your cursor over the picture.)

Thumbnail image of picture found for this day. APOD: 2009 January 27 - The Milky Way Over Mauna Kea
Explanation: Have you ever seen the band of our Milky Way Galaxy? In a clear sky from a dark location at the right time, a faint band of light becomes visible across the sky. Soon after your eyes become dark adapted, you might spot the band for the first time. It may then become obvious. Then spectacular. One reason for a growing astonishment might be the realization that this fuzzy swath contains billions of stars and is the disk of our very own spiral galaxy. Since we are inside this disk, the band appears to encircle the Earth. Visible in the above image, high above in the night sky, the band of the Milky Way Galaxy arcs. The bright spot just below the band is the planet Jupiter. In the foreground lies the moonlit caldera of the volcano Haleakala, located on the island of Maui in Hawaii, USA. A close look near the horizon will reveal light clouds and the dark but enormous Mauna Kea volcano on the Big Island of Hawaii. If you have never seen the Milky Way band or recognized the planet Jupiter, this year may be your chance. Because 2009 is the International Year of Astronomy, an opportunity to look through a window that peers deep into the universe may be coming to a location near you.

Thumbnail image of picture found for this day. APOD: 2008 December 11 - At the Center of the Milky Way
Explanation: At the center of our Milky Way Galaxy lies a supermassive black hole. Once a controversial claim, this conclusion is now solidly based on 16 years of observations that map the orbits of 28 stars very near the galactic center. Using European Southern Observatory telescopes and sophisticated near infrared cameras, astronomers patiently measured the positions of the stars over time, following one star, designated S2, through a complete orbit as it came within about 1 light-day of the center of the Milky Way. Their results convincingly show that S2 is moving under the influence of the enormous gravity of a compact, unseen object -- a black hole with 4 million times the mass of the Sun. Their ability to track stars so close to the galactic center accurately measures the black hole's mass and also determines the distance to the center to be 27,000 light-years. This deep, near-infrared image shows the crowded inner 3 light-years of the central Milky Way. Spectacular time-lapse animations of the stars orbiting within light-days of the galactic center can be found here.

Thumbnail image of picture found for this day. APOD: 2008 September 5 - Milky Way Road Trip
Explanation: In search of planets and the summer Milky Way, astronomer Tunç Tezel took an evening road trip. Last Saturday, after driving the winding road up Uludag, a mountain near Bursa, Turkey, he was rewarded by this beautiful skyview to the south. Near the center, bright planet Jupiter outshines the city lights below and the stars of the constellation Sagittarius. Above the mountain peaks, an arcing cloud bank seems to lead to the Milky Way's own cloudy apparition plunging into the distant horizon. In Turkish, Uludag means Great Mountain. Uludag was known in ancient times as the Mysian Olympus.

Thumbnail image of picture found for this day. APOD: 2008 July 29 - The Milky Way Over Ontario
Explanation: Sometimes, after your eyes adapt to the dark, a spectacular sky appears. Such was the case earlier this month over Ontario, Canada, when part of a spectacular sky also became visible in a reflection off a lake. To start, the brightest objects visible are bright stars and the planet Jupiter, seen as the brightest spot on the upper left. A distant town appears as a diffuse glow over the horizon. More faint still, the disk of the Milky Way Galaxy becomes apparent as a dramatic diffuse band across the sky that seems to crash into the horizon far in the distance. In the foreground, a picturesque landscape includes trees, a lake, and a stone wall. Finally, on this serene night in July when the lake water was unusually calm, reflections appear. Visible in the lake are not only reflections of several bright stars, but part of the Milky Way band itself. Careful inspection of the image will reveal, however, that bright stars leave small trails in the lake reflections that do not appear in the sky above. The reason for this is because the above image is actually a digital composite of time-consecutive exposures from the same camera. In the first set of exposures, sky images were co-added with slight rotations to keep the stars in one place.

Thumbnail image of picture found for this day. APOD: 2008 July 11 - The Far 3kpc Arm
Explanation: A major discovery was lurking in the data. By accident, while preparing a talk on the Galaxy's spiral arms for a meeting of the American Astronomical Society, Tom Dame (Harvard-Smithsonian CfA) found it - a new spiral arm in the Milky Way. The arm is labeled in this illustration as the Far 3kpc Arm, located at a distance of 3 kpc (kiloparsecs) or about 10,000 light-years from the galactic center, on the opposite side from the Sun. Along with the Near 3kpc Arm whose presence was known since the mid 1950s, the counterpart inner arms now establish that the galaxy has a simple symmetry. The arms are defined by shocked interstellar gas flowing along both sides of the Milky Way's central bar. Dame and his collaborator Patrick Thaddeus recorded the presence of both inner spiral arms in their radio data tracking emission from carbon monoxide molecules along the galactic plane. How much star formation goes on in the counterpart arms? Despite this depiction of stars and star forming regions along the arms, the last attempt to search for star formation in the Near 3kpc Arm was in 1980 and didn't turn up any. The discovery of the Far 3kpc Arm has renewed interest in this and other questions about the center of the Milky Way.

Thumbnail image of picture found for this day. APOD: 2008 June 6 - Two-Armed Spiral Milky Way
Explanation: Gazing out from within the Milky Way, our own galaxy's true structure is difficult to discern. But an ambitious survey effort with the Spitzer Space Telescope now offers convincing evidence that we live in a large galaxy distinguished by two main spiral arms (the Scutum-Centaurus and Perseus arms) emerging from the ends of a large central bar. In fact, from a vantage point that viewed our galaxy face-on, astronomers in distant galaxies would likely see the Milky Way as a two-armed barred spiral similar to this artist's illustration. Previous investigations have identified a smaller central barred structure and four spiral arms. Astronomers still place the Sun about a third of the way in from the Milky Way's outer edge, in a minor arm called the Orion Spur. To locate the Sun and identify the Milky Way's newly mapped features, just place your cursor over the image.

Thumbnail image of picture found for this day. APOD: 2008 June 5 - Spitzer's Milky Way
Explanation: The Spitzer Space Telescope's encompasing infrared view of the plane of our Milky Way Galaxy is hard to appreciate in just one picture. In fact, more than 800,000 frames of data from Spitzer's cameras have now been pieced together in an enormous mosaic of the galactic plane - the most detailed infrared picture of our galaxy ever made. The small portion seen here spans nearly 8 degrees, roughly the apparent width of your fist held at arms length, across the galaxy's center. The full mosaic is 120 degrees wide. Highlighted in the false-color presentation are curving green filaments of light from complex molecules - polycyclic aromatic hydrocarbons (PAHs) - that on Earth are the common, sooty products of incomplete combustion. The PAHs are found in star forming regions, along with reddish emission from graphite dust particles. Blue specks throughout the picture are individual Milky Way stars.

Thumbnail image of picture found for this day. APOD: 2008 May 3 - Alborz Mountain Milky Way
Explanation: Snow-capped stratovolcano Mt. Damavand climbs to 5,670 meters (18,598 feet) near the left edge in this panoramic view of the world at night. In the sky to the left of Damavand's peak are the stars of the Big Dipper in Ursa Major. Pan to the right and your gaze will sweep across the arch of our Milky Way Galaxy above the Alborz Mountain Range bordering the Caspian Sea. Near the center of the panorama, recorded in the predawn hours of April 4th, bright stars Deneb and Altair lie close to the curve of the Milky Way, above the glow of the Haraz valley. Farther right, brilliant Jupiter dominates the sky near the stars, nebulae, and dark dust clouds toward the bulging galactic center. Finally, the horizon glow at the right edge, below bright yellowish giant star Antares, is from the city of Damavand, named for the legendary mountain peak.

Thumbnail image of picture found for this day. APOD: 2008 January 4 - The Milky Way at 5000 Meters
Explanation: Climb up to 5000 meters (16,500 feet) above sea level, near Cerro Chajnantor in the northern Chilean Andes, and your night sky could encompass this cosmic vista. Recorded from that high and dry locale, the spectacular fish-eye image features the myriad stars and sprawling dust clouds of our Milky Way Galaxy. The direction toward the center of the Galaxy is near the zenith and center of the picture, but the Galactic Center itself is hidden from view, located far behind the obscuring dust. Brilliant Jupiter rules this scene just above the Milky Way's central bulge with the noticeably fainter, yellowish, giant star Antares to its right. Small and faint, near the right edge of the picture is one of the Milky Way's many satellite galaxies, the Small Magellanic Cloud.

Thumbnail image of picture found for this day. APOD: 2007 October 20 - The Milky Road
Explanation: Inspired during a visit to Fort Davis, Texas, home of McDonald Observatory and dark night skies, photographer Larry Landolfi created this tantalizing fantasy view. The composited image suggests the Milky Way is a heavenly extension of a deserted country road. Of course, the name for our galaxy, the Milky Way (in Latin, Via Lactea), does refer to its appearance as a milky band or path in the sky. In fact, the word galaxy itself derives from the Greek for milk. Visible on moonless nights from dark sky areas, though not so colorful as in this image, the glowing celestial band is due to the collective light of myriad stars along the plane of our galaxy, too faint to be distinguished individually. The diffuse starlight is cut by dark swaths of obscuring galactic dust clouds. At the beginning of the 17th century, Galileo turned his telescope on the Milky Way and announced it to be composed of innumerable stars.

Thumbnail image of picture found for this day. APOD: 2007 September 30 - A Milky Way Band
Explanation: Most bright stars in our Milky Way Galaxy reside in a disk. Since our Sun also resides in this disk, these stars appear to us as a diffuse band that circles the sky. The above panorama of a northern band of the Milky Way's disk covers 90 degrees and is a digitally created mosaic of several independent exposures. Scrolling right will display the rest of this spectacular picture. Visible are many bright stars, dark dust lanes, red emission nebulae, blue reflection nebulae, and clusters of stars. In addition to all this matter that we can see, astronomers suspect there exists even more dark matter that we cannot see.

Thumbnail image of picture found for this day. APOD: 2007 May 25 - Jupiter, Vesta, and the Milky Way
Explanation: In this gorgeous skyscape, gas giant Jupiter along with the stars and cosmic dust clouds of the Milky Way hang over the southern horizon in the early morning hours as seen from Stagecoach, Colorado, USA. Recorded on Thursday, Jupiter is the brightest object near picture center. Along with the stunning Milky Way, Jupiter is hard to miss, but a careful inspection of the view also reveals main belt asteroid Vesta. Of all the asteroids Vesta is the brightest and is now just bright enough to be visible to the naked eye from locations with very dark, clear skies. Vesta (as well as Jupiter) appears relatively bright now because it is near opposition, literally opposite the Sun in planet Earth's sky and closest to Earth in its orbit. For Vesta, this opposition offers the best viewing in many years. The year 2007 also coincides with the 200th anniversary of the asteroid's discovery. Starting late next month, NASA plans to launch the Dawn mission intended to explore Vesta (and Ceres) and the main asteroid belt.

Thumbnail image of picture found for this day. APOD: 2007 May 17 - The Milky Way Near the Southern Cross
Explanation: The glow of the southern Milky Way and the well-known Southern Cross are featured in this colorful skyscape recorded in April over La Frontera, Chile. The Southern Cross (Crux) itself is at the right of the 20 degree wide field of view, topped by bright, yellowish star Gamma Crucis. A line from Gamma Crucis through the blue star at the bottom of the cross, Alpha Crucis, points toward the south celestial pole. Against faint Milky Way starlight, the dark expanse of the Coal Sack Nebula lies just left of the cross, while farther left along the Milky Way are the bright stars Hadar and Rigil Kentaurus, also known as Beta and Alpha Centauri. Blazing in the lower left, Alpha Cen is the closest star to the Sun, a mere 4.3 light-years distant. In fact, yellowish Alpha Cen is actually a triple star system that includes a sun-like star. Seen from Alpha Cen, our own Sun would be a bright yellowish star in the otherwise recognizable constellation Cassiopeia.

Thumbnail image of picture found for this day. APOD: 2007 January 23 - The Milky Way Over Paranal
Explanation: It's not the sky that's falling. More accurately, the Earth is rising. The Earth's rotation gives a continually changing view to all Earth observers, including those measuring the universe at the Paranal Observatory. The observatory's four, massive 8.2 meter telescope units are situated on top of the 2,600 meter high mountain, Cerro Paranal, in the dry Atacama Desert in northern Chile. The individual unit telescopes can be used separately or in combination. Their names, Antu, Kueyen, Melipal, and Yepun, are taken from the Mapuche language. Fittingly they translate to Sun, Moon, Evening Star, and Southern Cross. Together they are fittingly known as the European Southern Observatory's Very Large Telescope. A higher time resolution version of the above movie is available here.

Thumbnail image of picture found for this day. APOD: 2006 August 1 - The Milky Way over Utah
Explanation: If sometimes it appears that the entire Milky Way Galaxy is raining down on your head, do not despair. It happens twice a day. As the Sun rises in the East, wonders of the night sky become less bright than the sunlight scattered by our own Earth's atmosphere, and so fade from view. They will only rotate back into view when the Earth again eclipses our bright Sun at dusk. This battle between heaven and Earth was captured dramatically over a rock formation at Capitol Reef National Park Utah, USA in 2003 May. Dark dust, millions of stars, and bright glowing red gas highlight the plane of our Milky Way Galaxy, which lies on average thousands of light years behind Earth's mountains.

Thumbnail image of picture found for this day. APOD: 2005 December 16 - GLIMPSE the Milky Way
Explanation: Scroll right and gaze through the dusty plane of our Milky Way Galaxy in infrared light. The cosmic panorama is courtesy of the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) project and the Spitzer Space Telescope. The galactic plane itself runs through the middle of the false-color view that spans nine degrees (about 18 full moons) across the southern constellation Norma. Spitzer's infrared cameras see through much of the galaxy's obscuring dust revealing many new star clusters as well as star forming regions (bright white splotches) and hot interstellar hydrogen gas (greenish wisps). The pervasive red clouds are emission from dust and organic molecules, pocked with holes and bubbles blown by energetic outflows from massive stars. Intensely dark patches are regions of dust too dense for even Spitzer's infrared vision to penetrate.

Thumbnail image of picture found for this day. APOD: 2005 October 23 - At the Center of the Milky Way
Explanation: At the center of our Milky Way Galaxy lies a black hole with over 2 million times the mass of the Sun. Once a controversial claim, this astounding conclusion is now virtually inescapable and based on observations of stars orbiting very near the galactic center. Using one of the Paranal Observatory's very large telescopes and a sophisticated infrared camera, astronomers patiently followed the orbit of a particular star, designated S2, as it came within about 17 light-hours of the center of the Milky Way (about 3 times the radius of Pluto's orbit). Their results convincingly show that S2 is moving under the influence of the enormous gravity of an unseen object that must be extremely compact -- a supermassive black hole. This deep near-infrared image shows the crowded inner 2 light-years of the Milky Way with the exact position of the galactic center indicated by arrows. The ability to track stars so close to the galactic center can accurately measure the black hole's mass and perhaps even provide an unprecedented test of Einstein's theory of gravity as astronomers watch a star orbit a supermassive black hole.

Thumbnail image of picture found for this day. APOD: 2005 October 4 - The Milky Way in Stars and Dust
Explanation: The disk of our Milky Way Galaxy is home to hot nebulae, cold dust, and billions of stars. This disk can be seen from a dark location on Earth as a band of diffuse light across the sky. This band crosses the sky in dramatic fashion in the above series of wide angle sky exposures from Chile. The deepness of the exposures also brings to light a vast network of complex dust filaments. Dust is so plentiful that it obscures our Galaxy's center in visible light, hiding its true direction until discovered by other means early last century. The Galactic Center, though, is visible above as the thickest part of the disk. The diffuse glow comes from billions of older, fainter stars like our Sun, which are typically much older than the dust or any of the nebulae. One particularly photogenic area of darkness is the Pipe Nebula visible above the Galactic Center. Dark dust is not the dark matter than dominates our Galaxy -- that dark matter remains in a form yet unknown.

Thumbnail image of picture found for this day. APOD: 2005 August 25 - Barred Spiral Milky Way
Explanation: A recent survey of stars conducted with the Spitzer Space Telescope is convincing astronomers that our Milky Way Galaxy is not just your ordinary spiral galaxy anymore. Looking out from within the Galaxy's disk, the true structure of the Milky Way is difficult to discern. However, the penetrating infrared census of about 30 million stars indicates that the Galaxy is distinguished by a very large central bar some 27,000 light-years long. In fact, from a vantage point that viewed our galaxy face-on, astronomers in distant galaxies would likely see a striking barred spiral galaxy suggested in this artist's illustration. While previous investigations have identified a small central barred structure, the new results indicate that the Milky Way's large bar would make about a 45 degree angle with a line joining the Sun and the Galaxy's center. DON'T PANIC ... astronomers still place the Sun beyond the central bar region, about a third of the way in from the Milky Way's outer edge.

Thumbnail image of picture found for this day. APOD: 2005 August 15 - Perseid Meteors and the Milky Way
Explanation: Where will the next Perseid meteor appear? Sky enthusiasts who trekked outside for the Perseid meteor shower that peaked over the past few days typically had this question on their mind. The above movie, where the time-line has been digitally altered, captures part of that very mystery. Eight meteors from the night of August 12 and the morning of August 13 have been identified in the movie so far, seven of which are Perseids. Can you identify the non-Perseid meteor? Since all Perseid meteors appear to come from the constellation of Perseus, the non-Perseid meteor is the one that streaks in a different direction. Early reports are that this year's Perseids were unfortunately a bit disappointing. The above digital mosaic was taken from Alsace, France, with the photogenic band of our Milky Way Galaxy far in the background.

Thumbnail image of picture found for this day. APOD: 2005 June 5 - A Milky Way Band
Explanation: Most bright stars in our Milky Way Galaxy reside in a disk. Since our Sun also resides in this disk, these stars appear to us as a diffuse band that circles the sky. The above panorama of a northern band of the Milky Way's disk covers 90 degrees and is a digitally created mosaic of several independent exposures. Scrolling right will display the rest of this spectacular picture. Visible are many bright stars, dark dust lanes, red emission nebulae, blue reflection nebulae, and clusters of stars. In addition to all this matter that we can see, astronomers suspect there exists even more dark matter that we cannot see.

Thumbnail image of picture found for this day. APOD: 2005 May 29 - The Sagittarius Dwarf Tidal Stream
Explanation: Is our Milky Way Galaxy out to lunch? Recent wide field images and analyses now indicate that our home galaxy is actually still in the process of devouring one of its closer satellite neighbors. This unfortunate neighbor, the Sagittarius Dwarf galaxy, is now seen to be part of a larger Sagittarius Tidal Stream, a loose filament of stars, gas, and possibly dark matter that entangles the Milky Way. An artist's depiction of the stream is shown above. Speculation also holds that the Sagittarius Dwarf was once pulled through the Milky Way disk very close to our Sun's current location. An important resulting realization is that galaxies contain a jumble of clumps and filaments of both dim and dark matter.

Thumbnail image of picture found for this day. APOD: 2005 January 4 - Milky Way Illustrated
Explanation: What does our Milky Way Galaxy look like from afar? Since we are stuck inside, and since opaque dust truncates our view in visible light, nobody knows for sure. Drawn above, however, is a good guess based on many different types of observations. In the Milky Way's center is a very bright core region centered on a large black hole. The Milky Way's bright central bulge is now thought to be an asymmetrical bar of relatively old and red stars. The outer regions are where the spiral arms are found, dominated in appearance by open clusters of young, bright, blue stars, by red emission nebula, and by dark dust. The spiral arms reside in a disk dominated in mass by relatively dim stars and loose gas composed mostly of hydrogen. What is not depicted is a huge spherical halo of invisible dark matter that dominates the mass of the Milky Way as well as the motions of stars away from the center.

Thumbnail image of picture found for this day. APOD: 2003 August 25 - The Northern Milky Way
Explanation: Many of the stars in our home Milky Way Galaxy appear together as a dim band on the sky that passes nearly over the Earth's north and south poles. Pictured above is the part of our Galaxy that passes closest over the north pole. Placing your cursor over the image will bring up the names of several constellations and bright stars. The diffuse white Galaxy glow is created by billions of stars, while red patches are large emission nebulas, usually marking areas where bright stars have recently formed. In the north, all of the lights visible at night and all lights that created this image were emitted within the past few thousand years from within the Milky Way Galaxy -- except one. On the upper right is a small faint patch designated M31, the Andromeda Galaxy. M31 is a spiral galaxy similar to our Milky Way but so distant it emits the oldest light distinguishable by the unaided eye -- light that takes over two million years to reach us.

Thumbnail image of picture found for this day. APOD: 2003 July 12 - X-Ray Milky Way
Explanation: If you had x-ray vision, the center regions of our Galaxy would not be hidden from view by the immense cosmic dust clouds opaque to visible light. Instead, the Milky Way toward Sagittarius might look something like this stunning mosaic of images from the orbiting Chandra Observatory. Pleasing to look at, the gorgeous false-color representation of the x-ray data shows high energy x-rays in blue, medium energies in green, and low energies in red. Hundreds of white dwarf stars, neutron stars, and black holes immersed in a fog of multimillion-degree gas are included in the x-ray vista. Within the white patch at the image center lies the Galaxy's central supermassive black hole. Chandra's sharp x-ray vision will likely lead to a new appreciation of our Milky Way's most active neighborhood and has already indicated that the hot gas itself may have a temperature of a mere 10 million degrees Celsius instead of 100 million degrees as previously thought. The full mosaic is composed of 30 separate images and covers a 900 by 400 light-year swath at the galactic center.

Thumbnail image of picture found for this day. APOD: 2003 June 3 - The Milky Way Behind an Eclipsed Moon
Explanation: What's behind the Moon? Each month, our Moon passes in front of -- and outshines -- many an interesting star field. Exceptions occur during a new Moon and during a total eclipse. In the background of a new Moon is usually the Sun, an even brighter orb that even more easily outshines everything behind it, except during a total solar eclipse. Even the longest total solar eclipse lasts just a few minutes, while the Sun's corona still remains bright. During a total lunar eclipse, however, the full Moon dims and a majestic star field may present itself for an hour or more. Such was the case during the middle of last month, when a rare glimpse of an eclipsed Moon superposed in front of the disk of our home Milky Way Galaxy was captured. Although fully in the Earth's shadow, the eclipsed Moon is still the brightest object on the right. The above image was captured during sub-zero weather from the Teide 2003 expedition to Mirador del Pico Viejo, a mountain in the Canary Islands, Spain, off the northwest coast of Africa.

Thumbnail image of picture found for this day. APOD: 2002 October 18 - At the Center of the Milk Way
Explanation: At the center of our Milky Way Galaxy lies a black hole with over 2 million times the mass of the Sun. Once a controversial claim, this astounding conclusion is now virtually inescapable and based on observations of stars orbiting very near the galactic center. Using one of the Paranal Observatory's very large telescopes and the sophisticated infrared camera NACO, astronomers patiently followed the orbit of a particular star, designated S2, as it came within about 17 light-hours of the center of the Milky Way (17 light-hours is only about 3 times the radius of Pluto's orbit). Their results convincingly show that S2 is moving under the influence of the enormous gravity of an unseen object which must be extremely compact -- a supermassive black hole. This deep NACO near-infrared image shows the crowded inner 2 light-years of the Milky Way with the exact position of the galactic center indicated by arrows. NACO's ability to track stars so close to the galactic center can accurately measure the black hole's mass and perhaps even provide an unprecedented test of Einstein's theory of gravity as astronomers watch a star orbit a supermassive black hole.

Thumbnail image of picture found for this day. APOD: 2002 September 23 - The Milky Way Over the French Alps
Explanation: Have you ever seen the band of our Milky Way Galaxy? Chances are you have never seen it like this -- nor could you. In a clear sky from a dark location at the right time, a faint band of light is visible across the sky. This band is the disk of our spiral galaxy. Since we are inside this disk, the band appears to encircle the Earth. The above spectacular picture is a bit of a digital trick, though. A first shot was taken in July 2000 with the camera counter-rotating from the Earth so that the stars appear fixed. This allowed a long exposure from which a great amount of detail could emerge from the background star field. Later, after moonrise, a much shorter image was taken from the same location catching details of the French Alps near Mount Blanc, the highest mountain in Western Europe. Reflections in the water were later enhanced digitally.

Thumbnail image of picture found for this day. APOD: 2002 January 10 - X-Ray Milky Way
Explanation: If you had x-ray vision, the center regions of our Galaxy would not be hidden from view by immense cosmic dust clouds opaque to visible light. Instead, the Milky Way toward Sagittarius might look something like this stunning mosaic of images from the orbiting Chandra Observatory. Pleasing to look at, the gorgeous false-color representation of the x-ray data shows high energy x-rays in blue, medium energies in green, and low energies in red. Hundreds of white dwarf stars, neutron stars, and black holes immersed in a fog of multimillion-degree gas are included in the x-ray vista. Within the white patch at the image center lies the Galaxy's central supermassive black hole. Chandra's sharp x-ray vision will likely lead to a new appreciation of our Milky Way's most active neighborhood and has already indicated that the hot gas itself may have a temperature of a mere 10 million degrees Celsius instead of 100 million degrees as previously thought. The full mosaic is composed of 30 separate images and covers a 900 by 400 light-year swath at the galactic center.

Thumbnail image of picture found for this day. APOD: 2001 December 22 - Hot Stars in the Southern Milky Way
Explanation: Hot blue stars, red glowing hydrogen gas, and dark, obscuring dust clouds are strewn through this dramatic region of the Milky Way in the southern constellation of Ara (the Altar). About 4,000 light-years from Earth, the stars at the left are young, massive, and energetic. Their intense ultraviolet radiation is eating away at the nearby star forming cloud complex - ionizing the hydrogen gas and producing the characteristic red "hydrogen-alpha" glow. At right, visible within the dark dust nebula, is small cluster of newborn stars. This beautiful color picture is a composite of images made through blue, green, and hydrogen-alpha filters.

Thumbnail image of picture found for this day. APOD: 2001 July 12 - NGC 1850: Not Found in the Milky Way
Explanation: A mere 168,000 light-years distant, this large, lovely cluster of stars, NGC 1850, is located near the outskirts of the central bar structure in our neighboring galaxy, the Large Magellanic Cloud. A first glance at this Hubble Space Telescope composite image suggests that this cluster's size and shape are reminiscent of the ancient globular star clusters which roam our own Milky Way Galaxy's halo. But NGC 1850's stars are young ... making it a type of star cluster with no known counterpart in the Milky Way. NGC 1850 is also a double star cluster, with a second, compact cluster of stars visible here below and to the right of the large cluster's central region. Stars in the large cluster are estimated to be 50 million years young, while stars in the compact cluster are younger still, with an age of about 4 million years. In fact, the smaller cluster contains T-Tauri stars, thought to be low mass, solar-type stars still in the process of formation. The glowing nebula at the left, like the supernova remnants in our own galaxy, testifies to violent stellar explosions, indicating short-lived massive stars were also present in NGC 1850.

Thumbnail image of picture found for this day. APOD: 2001 June 27 - Moonlight, Mars and Milky Way
Explanation: Aloha and welcome to a breath-taking skyscape. In this celestial scene, a four day old Moon illuminates a dreamlike foreground while bright planet Mars (above center) rules and the Milky Way's cosmic clouds of stars and dust seem to stretch from horizon to horizon. The picture was taken on May 27th from what may be the best amateur astronomy observing site on planet Earth, near the Mauna Kea, Hawai'i Visitor Center, 9,600 feet above sea level. Remarkable in the volcanic foreground are moonlit clouds and an "ahu hoku" - a star marker or star altar - built up of rocks topped with a white piece of coral gently glowing in the moonlight. Now near its closest approach in 13 years, Mars still lingers between the Milky Way constellations of Sagittarius and Scorpius. High above the horizon by midnight, the Red Planet is exceptionally well placed for earthdwellers to admire it. Astrophotographer Barney Magrath comments that this splendid sky view represents one of the joys of photography itself. When making the time exposure he did not realize that the ahu hoku would become such a beautiful element in his celestial composition.

Thumbnail image of picture found for this day. APOD: 2001 February 2 - All-Sky Panorama
Explanation: This quite stunning panorama of the entire sky is a mosaic of 51 wide-angle photographs. Made over a three year period from locations in California (USA), South Africa, and Germany, the individual pictures were digitized and stitched together to create an apparently seamless 360 by 180 degree view. Using a mathematical prescription like one often used to map the whole Earth's surface onto a single flat image, the complete digital mosaic was distorted and projected onto an oval shape. The image is oriented so the plane of our Milky Way Galaxy runs horizontally through the middle with the Galactic center at image center and Galactic north at the top. Most striking are the "milky" bands of starlight from the multitude of stars in the galactic plane cut by the dark, obscuring dust clouds strewn through the local spiral arms. In fact, almost everything visible here is within our own Milky Way Galaxy. Two fuzzy patches in the lower right quadrant of the mosaic do correspond to external galaxies, though. Known as the Magellanic Clouds, these are small, nearby satellite galaxies of the magnificent Milky Way.

Thumbnail image of picture found for this day. APOD: 2000 June 18 - The Milky Way Near the Southern Cross
Explanation: This breathtaking patch of sky would be above you were you to stand at the South Pole of the Earth. Just above and to the right of this photograph's center are the four stars that mark the boundaries of the famous Southern Cross. At the top of this constellation, also known as The Crux, is the orange star Gamma Crucis. The band of stars, dust, and gas crossing the middle of the photograph is part our Milky Way Galaxy. In the very center of the photograph is the dark Coal Sack Nebula, and the bright nebula on the far right is the Carina Nebula. The Southern Cross is such a famous constellation that it is depicted on the national flag of Australia.

Thumbnail image of picture found for this day. APOD: 2000 January 30 - The Milky Way in Infrared
Explanation: At night, from a dark location, part of the clear sky looks milky. This unusual swath of dim light is generally visible during any month and from any location. Until the invention of the telescope, nobody really knew what the "Milky Way" was. About 300 years ago telescopes caused a startling revelation: the Milky Way was made of stars. Only 70 years ago, more powerful telescopes brought the further revelation that the Milky Way is only one galaxy among many. Now telescopes in space allow yet deeper understanding. The above picture was taken by the COBE satellite and shows the plane of our Galaxy in infrared light. The thin disk of our home spiral galaxy is clearly apparent, with stars appearing white and interstellar dust appearing red.

Thumbnail image of picture found for this day. APOD: December 14, 1999 - High Velocity Clouds and the Milky Way
Explanation: Where are these gas clouds going so quickly? High velocity clouds (HVCs) of gas have been seen for decades but their origins and destinations have remained mysterious. Recent measurements have now placed at least one of these clouds in the halo of our Milky Way Galaxy, while other measurements have determined the relative abundance of cloud elements. Of the two clouds measured, each appears to have a chemical abundance consistent with a different origin. One HVC has been measured to have very few heavy elements ("low metallically") compared to neighboring stars, while another HVC has been inferred to have a heavy element abundance more typical of neighboring stars. Hypotheses are therefore being investigated that some HVCs are local gas remnants being pushed away from our Galaxy by supernova explosions, while other HVCs are ancient dwarf galaxy remnants falling toward our Galaxy. The latter possibility is particularly interesting as it might help explain how our Galaxy can continue to make stars at the observed rate. Fast moving HVCs are circled in the above false-color mosaic.

Thumbnail image of picture found for this day. APOD: October 9, 1999 - The Frothy Milky Way
Explanation: Astronomers have discovered that looking at dust along the plane of our Milky Way Galaxy is a bit like looking into a frothy glass of beer. The dust between stars in our galaxy appears to be arranged like a foam with bubbles and voids -- churned by shocks and winds generated as stars cycle through their lives. This processed infrared image, based on data from NASA's IRAS satellite, maps the radiation from the edges of galactic dust clouds and reveals the complex distribution. The image covers an area of about 40x60 degrees centered on the galactic plane near the Cygnus region. It shows bright bubble-shaped and arc-like dust clouds around the supernova remnants and starbirth regions embedded in the galactic disk.

Thumbnail image of picture found for this day. APOD: May 7, 1999 - Hot Stars in the Southern Milky Way
Explanation: Hot blue stars, red glowing hydrogen gas, and dark, obscuring dust clouds are strewn through this dramatic region of the Milky Way in the southern constellation of Ara (the Altar). About 4,000 light-years from Earth, the stars at the left are young, massive, and energetic. Their intense ultraviolet radiation is eating away at the nearby star forming cloud complex - ionizing the hydrogen gas and producing the characteristic red "hydrogen-alpha" glow. At right, visible within the dark dust nebula, is small cluster of newborn stars. This beautiful color picture is a composite of images made through blue, green, and hydrogen-alpha filters.

Thumbnail image of picture found for this day. APOD: February 24, 1999 - A Milky Way Band
Explanation: Most bright stars in our Milky Way Galaxy reside in a disk. Since our Sun also resides in this disk, these stars appear to us as a diffuse band that circles the sky. The above panorama of a southern band of the Milky Way's disk was taken from Australia. A 40-minute exposure was used, and the colors were digitally enhanced. Visible are many bright stars, dark dust lanes, red emission nebulae, blue reflection nebulae, and clusters of stars. In addition to all this matter that we can see, astronomers suspect there exists even more dark matter that we cannot see.

Thumbnail image of picture found for this day. APOD: November 26, 1998 - Meteor Milky Way
Explanation: The bold, bright star patterns of Orion (right) are a familiar sight to even casual skygazers. But this gorgeous color photo also features a subtler spectacle - the faint stars of the Milky Way. A broad region of the Milky Way runs vertically through the picture with the striking red Rosette Nebula in bloom left of center. Cutting across this dim, diffuse band of stars which lie along the plane of our Galaxy is a meteor streak. It seems to pass just under the red-orange giant star Betelgeuse at Orion's shoulder. Astrophotographer Jeff Medkeff recorded this and other beautiful time exposures from a dark sky countryside southeast of Sierra Vista, Arizona USA, during November's Leonid meteor shower.

Thumbnail image of picture found for this day. APOD: August 26, 1998 - The Magellanic Stream
Explanation: Spanning the sky behind the majestic Clouds of Magellan is an unusual stream of gas: the Magellanic Stream. The origin of this gas might hold a clue to origin and fate of our Milky Way's most famous satellite galaxies: the LMC and the SMC. Two leading genesis hypotheses have surfaced: that the stream was created by gas stripped off these galaxies as they passed through the halo of our Milky Way, or that the stream was created by the differential gravitational tug of the Milky Way. Measurements of slight angular motions by the Hipparcos satellite have indicated that the Clouds are leading the Stream. Now, recent radio measurements have located fresh gas emerging from the Clouds, bolstering the later, tidal explanation. Most probably, in a few hundred million years, the Magellanic Clouds themselves will fall victim to this same tidal force.

Thumbnail image of picture found for this day. APOD: August 17, 1998 - Comet Hyakutake and the Milky Way
Explanation: Two years ago, the Great Comet of 1996, Comet Hyakutake, inched across our northern sky during its long orbit around the Sun. Visible above as the bright spot with the faint tail near the picture's center, Comet Hyakutake shares the stage with part of the central band of the Milky Way Galaxy, prominent in the picture's upper right. Also visible are Antares, the bright orange star in the upper right, Arcturus, the bright star on the lower left, and the Pipe Nebula, which is perhaps harder to find. Comet Hyakutake's unusually close approach to the Earth allowed astronomers to learn many things, including that comets can emit much X-ray light.

Thumbnail image of picture found for this day. APOD: July 29, 1998 - The High Energy Heart Of The Milky Way
Explanation: These high resolution false color pictures of the Galactic center region in high energy X-ray and gamma-ray light result from a very long exposure of roughly 3,000 hours performed from 1990 to 1997 by the French SIGMA telescope onboard the Russian GRANAT spacecraft. Each image covers a 14x14 degree field which includes most of the central bulge of our Milky Way Galaxy. The X-ray picture (left) reveals a cluster of sources releasing enormous amounts of energy. They are probably binary star systems where matter accretes onto a collapsed object, either a neutron star or a black hole. But according to recent theories, only those binary systems with black holes can radiate above X-ray energies -- in the gamma-ray regime. In that case, the SIGMA sources also shining in the gamma-ray picture (right) betray the presence of accreting stellar black holes! Surprisingly, no high energy source seems to coincide exactly with the Galactic center itself, located near the brightest source at the bottom of both pictures. This indicates that the large black hole thought to be lurking there is unexpectedly quiet at these energies.

Thumbnail image of picture found for this day. APOD: May 23, 1998 - 7,000 Stars And The Milky Way
Explanation: This panorama view of the sky is really a drawing. It was made in the 1950s under the supervision of astronomer Knut Lundmark at the Lund Observatory in Sweden. To create the picture, draftsmen used a mathematical distortion to map the entire sky onto an oval shaped image with the plane of our Milky Way Galaxy along the center and the north galactic pole at the top. 7,000 individual stars are shown as white dots, size indicating brightness. The "Milky Way" clouds, actually the combined light of dim, unresolved stars in the densely populated galactic plane, are accurately painted on, interrupted by dramatic dark dust lanes. The overall effect is photographic in quality and represents the visible sky. Can you identify any familiar landmarks or constellations? For starters, Orion is at the right edge of the picture, just below the galactic plane and the Large and Small Magellanic Clouds are visible as fuzzy patches in the lower right quadrant.

Thumbnail image of picture found for this day. APOD: May 2, 1998 - The Frothy Milky Way
Explanation: Astronomers have discovered that looking at dust along the plane of our Milky Way Galaxy is a bit like looking into a frothy glass of beer. The dust between stars in our galaxy appears to be arranged like a foam with bubbles and voids -- churned by shocks and winds generated as stars cycle through their lives. This processed infrared image, based on data from NASA's IRAS satellite, maps the radiation from the edges of galactic dust clouds and reveals the complex distribution. The image covers an area of about 40x60 degrees centered on the galactic plane near the Cygnus region. It shows bright bubble-shaped and arc-like dust clouds around the supernova remnants and starbirth regions embedded in the galactic disk.

Thumbnail image of picture found for this day. APOD: February 16, 1998 - Sagittarius Dwarf to Collide with Milky Way
Explanation: Our Galaxy is being invaded. Recent observations indicate that in the next 100 million years, the Sagittarius Dwarf galaxy will move though the disk of our own Milky Way Galaxy yet again . The Sagittarius Dwarf (Sgr), shown as the extended irregular shape below the Galactic Center, is the closest of 9 known small dwarf spheroidal galaxies that orbit our Galaxy. Don't worry, our Galaxy is not in danger, but no such assurances are issued for the Sagittarius Dwarf: the intense gravitational tidal forces might pull it apart. Oddly, however, Sgr's orbit indicates that is has been through our Galaxy several times before, and survived! One possibility is that Sgr contains a great deal of low-density dark matter that hold it together gravitationally during these collisions.

Thumbnail image of picture found for this day. APOD: December 29, 1997 - The Milky Way in Infrared
Explanation: At night, from a dark location, part of the clear sky looks milky. This unusual swath of dim light is generally visible during any month and from any location. Until the invention of the telescope, nobody really knew what the "Milky Way" was. About 300 years ago telescopes caused a startling revelation: the Milky Way was made of stars. Only 70 years ago, more powerful telescopes brought the further revelation that the Milky Way is only one galaxy among many. Now telescopes in space allow yet deeper understanding. The above picture was taken by the COBE satellite and shows the plane of our Galaxy in infrared light. The thin disk of our home spiral galaxy is clearly apparent, with stars appearing white and interstellar dust appearing red.

Thumbnail image of picture found for this day. APOD: November 5, 1997 - The Milky Way's Gamma-Ray Halo
Explanation: Our Milky Way galaxy appears to be surrounded by a halo of gamma rays. Gamma rays are the most energetic form of electromagnetic radiation, with more than a hundred thousand times the energy of visible light, but known gamma-ray sources don't account for the diffuse distribution of this high-energy glow. This surprising result is based on data from the EGRET instrument onboard the Compton Gamma Ray Observatory. In this false color all-sky image centered on the Milky Way, the brown and green regions indicate brighter, known sources of gamma-rays. The galactic center and plane clearly standout as do some distant galaxies seen near the top and bottom of the picture. The dim, blue regions above and below the plane correspond to our Galaxy's unexpected gamma-ray halo. What causes the halo? Future gamma-ray telescopes could solve this mystery. However, the excitement has already inspired tantalizing speculation about the solution including; collisions of low energy photons with high-energy cosmic rays, high energy electrons accelerated by a previous burst of Milky Way star formation, and exotic interacting particles which make up Dark Matter.

Thumbnail image of picture found for this day. APOD: October 3, 1997 - Comet Halley and the Milky Way
Explanation: Comet Halley was photographed superposed in front of the disk of our Milky Way Galaxy in 1986 by the Kuiper Airborne Observatory. Comet Halley is the bright white streak near this photograph's center. Comet Halley is the most famous comet in history, and returns to the inner Solar System every 76 years. Stars visible in our Milky Way Galaxy typically lie millions of times farther in the distance and orbit the Galactic center every 250 million years. Billions of comets are thought to orbit our Sun but most do not get close enough for us to see. Similarly, billions of stars orbit our Milky Way's center but do not get close enough for us to see.

Thumbnail image of picture found for this day. APOD: May 17, 1997 - 7,000 Stars and the Milky Way
Explanation: This panorama view of the sky is really a drawing. It was made in the 1940s under the supervision of astronomer Knut Lundmark at the Lund Observatory in Sweden. To create the picture, draftsmen used a mathematical distortion to map the entire sky onto an oval shaped image with the plane of our Milky Way Galaxy along the center and the north galactic pole at the top. 7,000 individual stars are shown as white dots, size indicating brightness. The "Milky Way" clouds, actually the combined light of dim, unresolved stars in the densely populated galactic plane, are accurately painted on, interrupted by dramatic dark dust lanes. The overall effect is photographic in quality and represents the visible sky. Can you identify any familiar landmarks or constellations? For starters, Orion is at the right edge of the picture, just below the galactic plane and the Large and Small Magellanic Clouds are visible as fuzzy patches in the lower right quadrant.

Thumbnail image of picture found for this day. APOD: April 30, 1997 - Milky Way Molecule Map
Explanation: Where are the Milky Way's gas clouds and where are they going? Stars form in gas clouds, and the motion of gas clouds tell us about the size and rotation speed of our own Milky Way Galaxy. But gas clouds are hard to detect - they are composed mostly of nearly invisible molecular hydrogen and helium. Fortunately, at least small amounts of heavier gases co-exist, one of them being carbon monoxide (CO), which is relatively easy to detect at radio wavelengths. Therefore, over the past decade, a team of astronomers have carefully mapped out the molecular sky to unprecedented clarity - to about four times previous resolution and about eight times previous sensitivity. The resulting map is shown above, rescaled and in false color, with dark blue being relatively low emission. The band of our Milky Way Galaxy spans the middle. The data have not only helped our understanding of the Galaxy, but highlight a few mysteries too. For example: what causes the rapid speed of the gas near the Galactic Center?

Thumbnail image of picture found for this day. APOD: April 24, 1997 - The Frothy Milky Way
Explanation: Astronomers have recently discovered that looking at dust along the plane of our Milky Way Galaxy is a bit like looking into a frothy glass of beer. The dust between stars in our galaxy is arranged like a foam with bubbles and voids -- apparently churned by shocks and winds generated as stars cycle through their lives. This processed infrared image, based on data from NASA's IRAS satellite, maps the radiation from the edges of galactic dust clouds and reveals the complex distribution. The image covers an area of about 40x60 degrees centered on the galactic plane near the Cygnus region. It shows bright bubble-shaped and arc-like dust clouds around the supernova remnants and starbirth regions embedded in the galactic disk.

Thumbnail image of picture found for this day. APOD: March 15, 1997 - The Milky Way's Center
Explanation: Although the Earth is round, our Galaxy appears truly flat. This was shown in dramatic fashion by the COsmic Background Explorer (COBE) satellite which produced this premier view of the central region of our own Milky Way Galaxy in infrared light in1990. The Milky Way is a typical spiral galaxy with a central bulge and extended disk of stars. However, gas and dust within the disk obscure visible wavelengths of light effectively preventing clear observations of the center. Since infrared wavelengths are less affected by the obscuring material, the Diffuse InfraRed Background Experiment (DIRBE) on board COBE was able to detected infrared light from stars surrounding the Galactic center and produce this image. Of course, the edge on perspective represents the view from the vicinity of our Sun, a star located in the disk about 30,000 light years out from the center. The DIRBE module used equipment cooled by a tub of liquid helium to detect the infrared light which, composed of wavelengths longer than red light, is invisible to the human eye.

Thumbnail image of picture found for this day. APOD: March 4, 1997 - Solar Wind And Milky Way
Explanation: The Sun is bright, so bright that it overwhelms the light from other stars even for most satellite-borne telescopes. But LASCO, a coronograph onboard the space-based SOHO Observatory, uses occulting disks to block the intense solar light and examine the tenuous, hot gases millions of miles above the Sun's surface. In this LASCO image from December 24, 1996, an occulting disk (center) and mechanical support (extending from the lower left) are visible along with the billowing Solar Wind. Appearing in the background are faint stars and obscuring dust clouds toward the center of our Milky Way Galaxy! The field of view covers about 16 degrees, corresponding to 28 million miles at the distance of the Sun - just under half the diameter of Mercury's orbit. A prominent dark interstellar dust cloud cuts through the Milky Way starfield running approximately south (lower right) to north. Blemishes on the image are camera streaks caused by charged particles.

Thumbnail image of picture found for this day. APOD: December 12, 1996 - The Milky Way Through the Summer Triangle
Explanation: There are more than a few stars in our Galaxy. The light from many of them combines to appear as a wisp of faint light across the night sky - the Milky Way. In the northern hemisphere, away from city lights and during the summer months, part of the Milky Way can be seen behind the Summer Triangle of stars - Deneb, Vega, and Altair. These are the brightest three stars in the above photograph, listed from left to right, respectively. If you could collect light in your eyes for 10 minutes at a time (instead of the usual 1/10th of a second), you might see something like the above photograph. Behind the Summer Triangle lies some of the vast star fields of our Milky Way Galaxy, containing literally billions of stars. The dark band across the middle that seems to divide the stars is actually interstellar dust, which absorbs more visible light than it emits and so appears dark.

Thumbnail image of picture found for this day. APOD: July 23, 1996 - Hale-Bopp, Jupiter, and the Milky Way
Explanation: Shining brightly, the mighty Jupiter rules this gorgeous Kodacolor photo of the Milky Way near Sagittarius. Astronomer Bill Keel took the picture earlier this month (July 7) while standing near the summit of Hawaii's Mauna Kea contemplating the sky in the direction of the center of the Galaxy (right of picture center). In addition to the gas giant planet, which is well placed for evening viewing, the image contains an impressive sampler of celestial goodies. Many famous emission nebulae are visible as reddish patches - M16, the Eagle nebula, is just above and right of center, with the Horseshoe nebula, M17, just below it and farther to the right. Also, look for the Lagoon Nebula, M8, as the brightest red patch at the right of the picture with the Trifid Nebula, M20, just above it and to the left. The milky glow of distant unresolved stars in the plane of our Galaxy (thus the term Milky Way) runs through the image cut by dark, absorbing, interstellar dust clouds. The much anticipated comet Hale-Bopp is also clearly visible. Where's the comet? Click on the picture to view the comet's location flanked by superposed vertical lines. The comet was discovered while still beyond the orbit of Jupiter a year ago today independently by Alan Hale and Thomas Bopp. Astronomers monitoring Hale-Bopp's activity report that having now brightened to almost 6th magnitude it is still on track for becoming an extremely bright naked-eye comet in early 1997.

Thumbnail image of picture found for this day. APOD: June 5, 1996 - Sagittarius and the Central Milky Way
Explanation: What does the center of our Milky Way Galaxy look like? No one knows! It is not possible to see the Galactic center in light our eyes are sensitive to because the thick dust in the plane of our Galaxy obscures it. If one looks in the direction of our Galaxy's center - which is toward the constellation of Sagittarius - many beautiful wonders become apparent, though. The center of the Milky Way is behind the center of the photo. Large dust lanes and star clouds dominate the picture. As many as 30 Messier Objects are visible, including all types of nebula and star clusters. Two notable nebula include the Lagoon Nebula (M8), a small red patch just above center, and slightly above this is the red and blue Trifid Nebula (M20). The lines through picture were caused by airplanes, and the dark objects in the foreground are trees.

Thumbnail image of picture found for this day. APOD: May 15, 1996 - The Milky Way Near the Northern Cross
Explanation: This beautiful image of the sky near the bright star Deneb (just above center) reveals the stars, nebulae, and dark clouds along the plane of our Milky Way Galaxy as seen from the northern hemisphere (near Columbia Missouri, USA). Just below Deneb lies the suggestively shaped North America emission nebula. Deneb is the brightest star in the constellation Cygnus, located in the tail of this celestial swan. Cygnus contains the asterism known as the Northern Cross and marks one side of the "Great Rift" in the Milky Way, a series of dark obscuring dust clouds which stretches on through the constellation Sagittarius. Deneb defines the top of the Northern Cross while the body of the cross extends past the upper right corner of the picture. Cygnus also harbors the most famous candidate for a black hole in our galaxy, Cygnus X-1.

Thumbnail image of picture found for this day. APOD: May 3, 1996 - The Milky Way Near the Southern Cross
Explanation: This breathtaking patch of sky would be above you were you to stand at the south pole of the Earth. Just above and to the right of the photograph's center are the four stars that mark the boundaries of the famous Southern Cross. At the top of this constellation, also known as "The Crux," is the orange star Gamma Crucis. The band of stars, dust, and gas crossing the middle of the photograph is part our Milky Way Galaxy. In the very center of the photograph is the dark Coal Sack Nebula, and the bright nebula on the far right is the Eta Carina Nebula. The southern cross is so famous a constellation that it is depicted on the Australian National Flag.

Thumbnail image of picture found for this day. APOD: February 13, 1996 - 7,000 Stars And The Milky Way
Explanation: This panorama view of the sky is really a drawing. It was made in the 1940s under the supervision of astronomer Knut Lundmark at the Lund Observatory in Sweden. To create the picture, draftsmen used a mathematical distortion to map the entire sky onto an oval shaped image with the plane of our Milky Way Galaxy along the center and the north galactic pole at the top. 7,000 individual stars are shown as white dots, size indicating brightness. The "Milky Way" clouds, actually the combined light of dim, unresolved stars in the densely populated galactic plane, are accurately painted on, interrupted by dramatic dark dust lanes. The overall effect is photographic in quality and represents the visible sky. Can you identify any familiar landmarks or constellations? For starters, Orion is at the right edge of the picture, just below the galactic plane and the Large and Small Magellanic Clouds are visible as fuzzy patches in the lower right quadrant.

Thumbnail image of picture found for this day. APOD: October 29, 1995 - Radioactive Clouds in the Milky Way
Explanation: When massive stars explode they create large radioactive blast clouds which expand into interstellar space. As the radioactive elements decay, they produce gamma-rays. Possible locations of these stellar explosions known as supernovae, are indicated by the bright clumps in this map of the central regions of our Milky Way Galaxy. The map was made by a telescope onboard NASA's orbiting Compton Gamma Ray Observatory using detectors sensitive to gamma rays from the decay of radioactive aluminum.

Thumbnail image of picture found for this day. APOD: September 8, 1995 - The Milky Way's Center
Explanation: NASA's COBE satellite scanned the heavens at infrared wavelengths in 1990 and produced this premier view of the central region of our own Milky Way Galaxy. The Milky Way is a typical spiral galaxy with a central bulge and extended disk of stars. However, gas and dust within the disk obscure visible wavelengths of light effectively preventing clear observations of the center. Since infrared wavelengths, are less affected by the obscuring material, the Diffuse InfraRed Background Experiment (DIRBE) on board COBE was able to detected infrared light from stars surrounding the galactic center and produce this image. Of course, the edge on perspective represents the view from the vicinity of our Sun, a star located in the disk about 30,000 light years out from the center. The DIRBE experiment used equipment cooled by a tub of liquid helium to detect the infrared light which, composed of wavelengths longer than red light, is invisible to the human eye.


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