Astronomy Picture of the Day Search Results for "2024"

APOD: 2025 June 20 – Major Lunar Standstill 2024-2025
Explanation: Edmonton, Alberta, Canada, planet Earth lies on the horizon in this stack of panoramic composite images. In a monthly time series arranged vertically top to bottom the ambitious photographic project follows the annual north-south swing of sunrise points, from June solstice to December solstice and back again. It also follows the corresponding, but definitely harder to track, Full Moon rise. Of course, the north-south swing of moonrise runs opposite sunrise along the horizon. But these rising Full Moons also span a wider range on the horizon than the sunrises. That's because the well-planned project (as shown in this video) covers the period June 2024 to June 2025, centered on a major lunar standstill. Major lunar standstills represent extremes in the north-south range of moonrise driven by the 18.6 year precession period of the lunar orbit.

APOD: 2025 January 2 - Solar Analemma 2024
Explanation: Recorded during 2024, this year-spanning series of images reveals a pattern in the seasonal drift of the Sun's daily motion through planet Earth's sky. Known to some as an analemma, the figure-eight curve was captured in exposures taken only at 1pm local time on clear days from Kayseri, Turkiye. Of course the Sun's position on the 2024 solstice dates was at the top and bottom of the curve. They correspond to the astronomical beginning of summer and winter in the north. The points along the curve half-way between the solstices, but not the figure-eight curve crossing point, mark the 2024 equinoxes and the start of spring and fall. Regional peaks and dormant volcano Mount Erciyes lie along the southern horizon in the 2024 timelapse skyscape.

APOD: 2024 December 31 – The Twisted Disk of NGC 4753
Explanation: What do you think this is? Here’s a clue: it's bigger than a bread box. Much bigger. The answer is that pictured NGC 4753 is a twisted disk galaxy, where unusual dark dust filaments provide clues about its history. No one is sure what happened, but a leading model holds that a relatively normal disk galaxy gravitationally ripped apart a dusty satellite galaxy while its precession distorted the plane of the accreted debris as it rotated. The cosmic collision is hypothesized to have started about a billion years ago. NGC 4753 is seen from the side, and possibly would look like a normal spiral galaxy from the top. The bright orange halo is composed of many older stars that might trace dark matter. The featured Hubble image was recently reprocessed to highlight ultraviolet and red-light emissions.

APOD: 2024 December 30 – M27: The Dumbbell Nebula
Explanation: Is this what will become of our Sun? Quite possibly. The first hint of our Sun's future was discovered inadvertently in 1764. At that time, Charles Messier was compiling a list of diffuse objects not to be confused with comets. The 27th object on Messier's list, now known as M27 or the Dumbbell Nebula, is a planetary nebula, one of the brightest planetary nebulas on the sky and visible with binoculars toward the constellation of the Fox (Vulpecula). It takes light about 1000 years to reach us from M27, featured here in colors emitted by sulfur (red), hydrogen (green) and oxygen (blue). We now know that in about 6 billion years, our Sun will shed its outer gases into a planetary nebula like M27, while its remaining center will become an X-ray hot white dwarf star. Understanding the physics and significance of M27 was well beyond 18th century science, though. Even today, many things remain mysterious about planetary nebulas, including how their intricate shapes are created.

APOD: 2024 December 29 – Methane Bubbles Frozen in Lake Baikal
Explanation: What are these bubbles frozen into Lake Baikal? Methane. Lake Baikal, a UNESCO World Heritage Site in Russia, is the world's largest (by volume), oldest, and deepest lake, containing over 20% of the world's fresh water. The lake is also a vast storehouse of methane, a greenhouse gas that, if released, could potentially increase the amount of infrared light absorbed by Earth's atmosphere, and so increase the average temperature of the entire planet. Fortunately, the amount of methane currently bubbling out is not climatologically important. It is not clear what would happen, though, were temperatures to significantly increase in the region, or if the water level in Lake Baikal were to drop. Pictured, bubbles of rising methane froze during winter into the exceptionally clear ice covering the lake.

APOD: 2024 December 27 - Planet Earth at Twilight
Explanation: No sudden, sharp boundary marks the passage of day into night in this gorgeous view of ocean and clouds over our fair planet Earth. Instead, the shadow line or terminator is diffuse and shows the gradual transition to darkness we experience as twilight. With the Sun illuminating the scene from the right, the cloud tops reflect gently reddened sunlight filtered through the dusty troposphere, the lowest layer of the planet's nurturing atmosphere. A clear high altitude layer, visible along the dayside's upper edge, scatters blue sunlight and fades into the blackness of space. This picture was taken from the International Space Station orbiting at an altitude of 211 nautical miles. Of course from home, you can check out the Earth Now.

APOD: 2024 December 23 – Christmas Tree Aurora
Explanation: It was December and the sky lit up like a Christmas tree. Shimmering, the vivid green, blue, and purple auroral colors that formed the tree-like apparition were caused by high atmospheric oxygen and nitrogen reacting to a burst of incoming electrons. Collisions caused the orbital electrons of atoms and molecules to jump into excited energy states and emit visible light when returning to their normal state. The featured image was captured in Djúpivogur, Iceland during the last month of 2023. Our Sun is currently in its most energetic phase of its 11-year cycle, with its high number of active regions and sunspots likely to last into next year. Of course, the Sun has been near solar maximum during this entire year, with its outbursts sometimes resulting in spectacular Earthly auroras.

APOD: 2024 December 22 – The Local Fluff
Explanation: The stars are not alone. In the disk of our Milky Way Galaxy, about 10 percent of visible matter is in the form of gas called the interstellar medium (ISM). The ISM is not uniform and shows patchiness even near our Sun. It can be quite difficult to detect the local ISM because it is so tenuous and emits so little light. This mostly hydrogen gas, however, absorbs some very specific colors that can be detected in the light of the nearest stars. A working map of the local ISM within 20 light-years, based on ongoing observations and particle detections from the Earth-orbiting Interstellar Boundary Explorer satellite (IBEX), is shown here. These observations indicate that our Sun is moving through a Local Interstellar Cloud as this cloud flows outwards from the Scorpius-Centaurus Association star forming region. Our Sun may exit the Local Cloud, also called the Local Fluff, during the next 10,000 years. Much remains unknown about the local ISM, including details of its distribution, its origin, and how it affects the Sun and the Earth. Unexpectedly, IBEX spacecraft measurements indicate that the direction from which neutral interstellar particles flow through our Solar System is changing.

APOD: 2024 December 21 - A Year in Sunsets
Explanation: A year in sunsets, from April 2023 to March 2024, track along the western horizon in these stacked panoramic views. The well-planned sequence is constructed of images recorded near the 21st day of the indicated month from the same location overlooking Cairo, Egypt. But for any location on planet Earth the yearly extreme northern (picture right) and southern limits of the setting Sun mark the solstice days. The word solstice is from Latin for "Sun" and "stand still". On the solstice date the seasonal drift of the Sun's daily path through the sky appears to pause and reverse direction in its annual celestial journey. Of course the Sun reaches a stand still on today's date. The 21 December 2024 solstice at 09:21 UTC is the moment of the Sun's southernmost declination, the start of astronomical winter in the north and summer in the south.

APOD: 2024 December 20 - The Long Night Moon
Explanation: On the night of December 15, the Full Moon was bright. Known to some as the Cold Moon or the Long Night Moon, it was the closest Full Moon to the northern winter solstice and the last Full Moon of 2024. This Full Moon was also at a major lunar standstill. A major lunar standstill is an extreme in the monthly north-south range of moonrise and moonset caused by the precession of the Moon's orbit over an 18.6 year cycle. As a result, the full lunar phase was near the Moon's northernmost moonrise (and moonset) along the horizon. December's Full Moon is rising in this stacked image, a composite of exposures recording the range of brightness visible to the eye on the northern winter night. Along with a colorful lunar corona and aircraft contrail this Long Night Moon shines in a cold sky above the rugged, snowy peaks of the Italian Dolomites.

APOD: 2024 December 17 – Near to the Heart Nebula
Explanation: What excites the Heart Nebula? First, the large emission nebula on the upper left, catalogued as IC 1805, looks somewhat like a human heart. The nebula glows brightly in red light emitted by its most prominent element, hydrogen, but this long-exposure image was also blended with light emitted by sulfur (yellow) and oxygen (blue). In the center of the Heart Nebula are young stars from the open star cluster Melotte 15 that are eroding away several picturesque dust pillars with their atom-exciting energetic light and winds. The Heart Nebula is located about 7,500 light years away toward the constellation of Cassiopeia. This wide field image shows much more, though, including the Fishhead Nebula just below the Heart, a supernova remnant on the lower left, and three planetary nebulas on the image right. Taken over 57 nights, this image is so deep, though, that it clearly shows fainter long and complex filaments.

APOD: 2024 December 16 – A Kilometer High Cliff on Comet Churyumov Gerasimenko
Explanation: This kilometer high cliff occurs on the surface of a comet. It was discovered on the dark nucleus of Comet Churyumov - Gerasimenko (CG) by Rosetta, a robotic spacecraft launched by ESA, which orbited the comet from 2014 to 2016. The ragged cliff, as featured here, was imaged by Rosetta early in its mission. Although towering about one kilometer high, the low surface gravity of Comet CG would likely make a jump from the cliffs by a human survivable. At the foot of the cliffs is relatively smooth terrain dotted with boulders as large as 20 meters across. Data from Rosetta indicates that the ice in Comet CG has a significantly different deuterium fraction -- and hence likely a different origin -- than the water in Earth's oceans. The probe was named after the Rosetta Stone, a rock slab featuring the same text written in three different languages that helped humanity decipher ancient Egyptian writing.

APOD: 2024 December 15 – Geminid Meteors over a Snowy Forest
Explanation: Meteors have been flowing out from the constellation Gemini. This was expected, as mid-December is the time of the Geminid Meteor Shower. Pictured here, over two dozen meteors were caught in successively added exposures taken over several hours early Saturday morning from a snowy forest in Poland. The fleeting streaks were bright enough to be seen over the din of the nearly full Moon on the upper right. These streaks can all be traced back to a point on the sky called the radiant toward the bright stars Pollux and Castor in the image center. The Geminid meteors started as sand sized bits expelled from asteroid 3200 Phaethon during its elliptical orbit through the inner Solar System.

APOD: 2024 December 13 - M51: Tidal Streams and H-alpha Cliffs
Explanation: An intriguing pair of interacting galaxies, M51 is the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with whirlpool-like spiral structure seen nearly face-on is also cataloged as NGC 5194. Its spiral arms and dust lanes sweep in front of its smaller companion galaxy, NGC 5195. Some 31 million light-years distant, within the boundaries of the well-trained constellation Canes Venatici, M51 looks faint and fuzzy to the eye in direct telescopic views. But this remarkably deep image shows off stunning details of the galaxy pair's striking colors and fainter tidal streams. The image includes extensive narrowband data to highlight a vast reddish cloud of ionized hydrogen gas recently discovered in the M51 system and known to some as the H-alpha cliffs. Foreground dust clouds in the Milky Way and distant background galaxies are captured in the wide-field view. A continuing collaboration of astro-imagers using telescopes on planet Earth assembled over 3 weeks of exposure time to create this evolving portrait of M51.

APOD: 2024 December 12 - Phaethon s Brood
Explanation: Based on its well-measured orbit, 3200 Phaethon (sounds like FAY-eh-thon) is recognized as the source of the meteoroid stream responsible for the annual Geminid meteor shower. Even though most meteor shower parents are comets, 3200 Phaethon is a known and closely tracked near-Earth asteroid with a 1.4 year orbital period. Rocky and sun-baked, its perihelion or closest approach to the Sun is well within the orbit of innermost planet Mercury. In this telescopic field of view, the asteroid's rapid motion against faint background stars of the heroic constellation Perseus left a short trail during the two minute total exposure time. The (faint) parallel streaks of its meteoric children flashed much more quickly across the scene. The family portrait was recorded near the Geminid meteor shower's very active peak on 2017 December 13. That was just three days before 3200 Phaethon's historic close approach to planet Earth. This year, the night of December 13 should again see the peak of the Geminid meteor shower, but faint meteors will be washed out by the bright light of the nearly full moon.

APOD: 2024 December 9 – Pleiades: The Seven Sisters Star Cluster
Explanation: Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as large and clear as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen with the unaided eye even from the depths of a light-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The featured 23-hour exposure, taken from Fagagna, Italy covers a sky area several times the size of the full moon. Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus). A common legend with a modern twist is that one of the brighter stars faded since the cluster was named, leaving only six of the sister stars visible to the unaided eye. The actual number of Pleiades stars visible, however, may be more or less than seven, depending on the darkness of the surrounding sky and the clarity of the observer's eyesight.

APOD: 2024 December 6 - Xuyi Station and the Fireball
Explanation: Colorful and bright, this streaking fireball meteor was captured in a single exposure taken at Purple Mountain (Tsuchinshan) Observatory’s Xuyi Station in 2020, during planet Earth's annual Perseid meteor shower. The dome in the foreground houses the China Near Earth Object Survey Telescope (CNEOST), the largest multi-purpose Schmidt telescope in China. Located in Xuyi County, Jiangsu Province, the station began its operation as an extension of China's Purple Mountain Observatory in 2006. Darling of planet Earth's night skies in 2024, the bright comet designated Tsuchinshan-ATLAS (C/2023 A3) was discovered in images taken there on 2023 January 9. The discovery is jointly credited to NASA's ATLAS robotic survey telescope at Sutherland Observatory, South Africa. Other comet discoveries associated with the historic Purple Mountain Observatory and bearing the observatory's transliterated Mandarin name include periodic comets 60/P Tsuchinshan and 62/P Tsuchinshan.

APOD: 2024 December 5 - Stereo Jupiter near Opposition
Explanation: Jupiter looks sharp in these two rooftop telescope images. Both were captured last year on November 17 from Singapore, planet Earth, about two weeks after Jupiter's 2023 opposition. Climbing high in midnight skies the giant planet was a mere 33.4 light-minutes from Singapore. That's about 4 astronomical units away. Jupiter's planet girdling dark belts and light zones are visible in remarkable detail, along with the giant world's whitish oval vortices. Its signature Great Red Spot is prominent in the south. Jupiter rotates rapidly on its axis once every 10 hours. So, based on video frames taken only 15 minutes apart, these images form a stereo pair. Look at the center of the pair and cross your eyes until the separate images come together to see the 3D effect. Of course Jupiter is now not far from its 2024 opposition. Planet Earth is set to pass between the Solar System's ruling gas giant and the Sun on December 7.

APOD: 2024 December 4 – Driveway Analemma
Explanation: Does the Sun return to the same spot on the sky every day?  No.  A more visual answer is an analemma, a composite of sky images taken at the same time and from the same place over a year.  At completion, you can see that the Sun makes a figure 8 on the sky. The featured unusual analemma does not, however, picture the Sun directly: it was created by looking in the opposite direction. All that was required was noting where the shadow of an edge of a house was in the driveway every clear day at the same time. Starting in March in Falcon, Colorado, USA, the photographer methodically marked the shadow's 1 pm location. In one frame you can even see the photographer himself. Although this analemma will be completed in 2025, you can start drawing your own driveway analemma -- using no fancy equipment -- as soon as today.

APOD: 2024 December 1 – Cosmic Latte: The Average Color of the Universe
Explanation: What color is the universe? More precisely, if the entire sky were smeared out, what color would the final mix be? This whimsical question came up when trying to determine what stars are commonplace in nearby galaxies. The answer, depicted here, is a conditionally perceived shade of beige. In computer parlance: #FFF8E7. To determine this, astronomers computationally averaged the light emitted by one of the larger samples of galaxies analyzed: the 200,000 galaxies of the 2dF Galaxy Redshift Survey. The resulting cosmic spectrum has some emission in all parts of the electromagnetic spectrum, but a single perceived composite color. This color has become much less blue over the past 10 billion years, indicating that redder stars are becoming more prevalent. In a contest to better name the color, notable entries included skyvory, univeige, and the winner: cosmic latte.

APOD: 2024 November 27 – The Meteor and the Comet
Explanation: How different are these two streaks? The streak on the upper right is Comet Tsuchinshan-Atlas showing an impressive dust tail. The comet is a large and dirty iceberg that entered the inner Solar System and is shedding gas and dust as it is warmed by the Sun's light. The streak on the lower left is a meteor showing an impressive evaporation trail. The meteor is a small and cold rock that entered the Earth's atmosphere and is shedding gas and dust as it is warmed by molecular collisions. The meteor was likely once part of a comet or asteroid -- perhaps later composing part of its tail. The meteor was gone in a flash and was only caught by coincidence during a series of exposures documenting the comet's long tail. The featured image was captured just over a month ago from Sichuan Province in China.

APOD: 2024 November 25 – The Horsehead Nebula
Explanation: One of the most identifiable nebulas in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. Light takes about 1,500 years to reach us from the Horsehead Nebula. The featured image was taken from the Chilescope Observatory in the mountains of Chile.

APOD: 2024 November 24 – Journey to the Center of the Galaxy
Explanation: What lies at the center of our galaxy? In Jules Verne's science fiction classic, A Journey to the Center of the Earth, Professor Liedenbrock and his fellow explorers encounter many strange and exciting wonders. Astronomers already know of some of the bizarre objects that exist at our Galactic Center, including vast cosmic dust clouds, bright star clusters, swirling rings of gas, and even a supermassive black hole. Much of the Galactic Center is shielded from our view in visible light by the intervening dust and gas, but it can be explored using other forms of electromagnetic radiation. The featured video is actually a digital zoom into the Milky Way's center which starts by utilizing visible light images from the Digitized Sky Survey. As the movie proceeds, the light shown shifts to dust-penetrating infrared and highlights gas clouds that were recently discovered in 2013 to be falling toward the central black hole.

APOD: 2024 November 20 - Earthset from Orion
Explanation: Eight billion people are about to disappear in this snapshot from space taken on 2022 November 21. On the sixth day of the Artemis I mission, their home world is setting behind the Moon's bright edge as viewed by an external camera on the outbound Orion spacecraft. Orion was headed for a powered flyby that took it to within 130 kilometers of the lunar surface. Velocity gained in the flyby maneuver was used to reach a distant retrograde orbit around the Moon. That orbit is considered distant because it's another 92,000 kilometers beyond the Moon, and retrograde because the spacecraft orbited in the opposite direction of the Moon's orbit around planet Earth. Orion entered its distant retrograde orbit on November 25. Swinging around the Moon, Orion reached a maximum distance (just over 400,000 kilometers) from Earth on November 28, exceeding a record set by Apollo 13 for most distant spacecraft designed for human space exploration. The Artemis II mission, carrying 4 astronauts around the moon and back again, is scheduled to launch no earlier than September 2025.

APOD: 2024 November 17 – LDN 1471: A Windblown Star Cavity
Explanation: What is the cause of this unusual parabolic structure? This illuminated cavity, known as LDN 1471, was created by a newly forming star, seen as the bright source at the peak of the parabola. This protostar is experiencing a stellar outflow which is then interacting with the surrounding material in the Perseus Molecular Cloud, causing it to brighten. We see only one side of the cavity -- the other side is hidden by dark dust. The parabolic shape is caused by the widening of the stellar-wind blown cavity over time. Two additional structures can also be seen either side of the protostar; these are known as Herbig-Haro objects, again caused by the interaction of the outflow with the surrounding material. What causes the striations on the cavity walls, though, remains unknown. The featured image was taken by NASA and ESA’s Hubble Space Telescope after an original detection by the Spitzer Space Telescope.

APOD: 2024 November 16 - Pluto at Night
Explanation: The night side of Pluto spans this shadowy scene. In the stunning spacebased perspective the Sun is 4.9 billion kilometers (almost 4.5 light-hours) behind the dim and distant world. It was captured by far flung New Horizons in July of 2015 when the spacecraft was at a range of some 21,000 kilometers from Pluto, about 19 minutes after its closest approach. A denizen of the Kuiper Belt in dramatic silhouette, the image also reveals Pluto's tenuous, surprisingly complex layers of hazy atmosphere. Near the top of the frame the crescent twilight landscape includes southern areas of nitrogen ice plains now formally known as Sputnik Planitia and rugged mountains of water-ice in the Norgay Montes.

APOD: 2024 November 14 - IC 348 and Barnard 3
Explanation: A great nebulous region near bright star omicron Persei offers this study in cosmic contrasts. Captured in the telescopic frame is a colorful complex of dust, gas, and stars spanning about 3 degrees on the sky along the edge of the Perseus molecular cloud, some 1000 light-years away. Surrounded by a bluish halo of dust-reflected starlight, omicron Persei itself is just left of center. Immediately below it lies the intriguing young star cluster IC 348 recently explored at infrared wavelengths by the James Webb Space Telescope. In silhouette against the diffuse reddish glow of hydrogen gas, dark and obscuring interstellar dust cloud Barnard 3 is at upper right. Of course, the cosmic dust also tends to hide newly formed stars and young stellar objects or protostars from prying optical telescopes. At the Perseus molecular cloud's estimated distance, this field of view would span about 50 light-years.

APOD: 2024 November 11 – The Unusual Tails of Comet Tsuchinshan Atlas
Explanation: What created an unusual dark streak in Comet Tsuchinshan-Atlas's tail? Some images of the bright comet during mid-October not only caught its impressively long tail and its thin anti-tail, but a rather unexpected feature: a dark streak in the long tail. The reason for the dark streak is currently unclear and a topic of some debate. Possible reasons include a plume of dark dust, different parts of the bright tail being unusually superposed, and a shadow of a dense part of the coma on smaller dust particles. The streak is visible in the featured image taken on October 14 from Texas, USA. To help future analyses, if you have taken a good image of the comet that clearly shows this dark streak, please send it in to APOD. Comet Tsuchinshan–ATLAS has now faded considerably and is returning to the outer Solar System.

APOD: 2024 November 9 - Neptune at Night
Explanation: Ice giant Neptune is faint in Earth's night sky. Some 30 times farther from the Sun than our fair planet, telescopes are needed to catch a glimpse of the dim and distant world. This dramatic view of Neptune's night just isn't possible for telescopes in the vicinity of planet Earth though. Peering out from the inner Solar System they can only bring Neptune's day side into view. In fact this night side image with Neptune's slender crescent next to the crescent of its large moon Triton was captured by Voyager 2. Launched from planet Earth in 1977 the Voyager 2 spacecraft made a close fly by of the Solar System's outermost planet in 1989, looking back on Neptune at night as the robotic spacecraft continued its voyage to interstellar space.

APOD: 2024 November 6 – Comet Tsuchinshan Atlas over the Dolomites
Explanation: Comet Tsuchinshan-Atlas is now headed back to the outer Solar System. The massive dusty snowball put on quite a show during its trip near the Sun, resulting in many impressive pictures from planet Earth during October. The featured image was taken in mid-October and shows a defining visual feature of the comet -- its impressive anti-tail. The image captures Comet C/2023 A3 (Tsuchinshan–ATLAS) with impressively long dust and ion tails pointing up and away from the Sun, while the strong anti-tail -- composed of more massive dust particles -- trails the comet and points down and (nearly) toward the recently-set Sun. In the foreground is village of Tai di Cadore, Italy, with the tremendous Dolomite Mountains in the background. Another comet, C/2024 S1 (ATLAS), once a candidate to rival Comet Tsuchinshan-Atlas in brightness, broke up last week during its close approach to our Sun.

APOD: 2024 November 4 – M42: The Great Nebula in Orion
Explanation: The Great Nebula in Orion, an immense, nearby starbirth region, is probably the most famous of all astronomical nebulas. Here, glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1500 light-years away. In the featured deep image in assigned colors highlighted by emission in oxygen and hydrogen, wisps and sheets of dust and gas are particularly evident. The Great Nebula in Orion can be found with the unaided eye near the easily identifiable belt of three stars in the popular constellation Orion. In addition to housing a bright open cluster of stars known as the Trapezium, the Orion Nebula contains many stellar nurseries. These nurseries contain much hydrogen gas, hot young stars, proplyds, and stellar jets spewing material at high speeds. Also known as M42, the Orion Nebula spans about 40 light years and is located in the same spiral arm of our Galaxy as the Sun.

APOD: 2024 October 29 – NGC 602: Stars Versus Pillars from Webb
Explanation: The stars are destroying the pillars. More specifically, some of the newly formed stars in the image center are emitting light so energetic that is evaporating the gas and dust in the surrounding pillars. Simultaneously, the pillars themselves are still trying to form new stars. The whole setting is the star cluster NGC 602, and this new vista was taken by the Webb Space Telescope in multiple infrared colors. In comparison, a roll-over image shows the same star cluster in visible light, taken previously by the Hubble Space Telescope. NGC 602 is located near the perimeter of the Small Magellanic Cloud (SMC), a small satellite galaxy of our Milky Way galaxy. At the estimated distance of the SMC, the featured picture spans about 200 light-years. A tantalizing assortment of background galaxies are also visible -- mostly around the edges -- that are at least hundreds of millions of light-years beyond.

APOD: 2024 October 28 – STEVE: A Glowing River over France
Explanation: Sometimes a river of hot gas flows over your head. In this case the river created a Strong Thermal Emission Velocity Enhancement (STEVE) that glowed bright red, white, and pink. Details of how STEVEs work remain a topic of research, but recent evidence holds that their glow results from a fast-moving river of hot ions flowing over a hundred kilometers up in the Earth's atmosphere: the ionosphere. The more expansive dull red glow might be related to the flowing STEVE, but alternatively might be a Stable Auroral Red (SAR) arc, a more general heat-related glow. The featured picture, taken earlier this month in Côte d'Opale, France, is a wide-angle digital composite made as the STEVE arc formed nearly overhead. Although the apparition lasted only a few minutes, this was long enough for the quick-thinking astrophotographer to get in the picture -- can you find him?

APOD: 2024 October 25 - Globular Star Cluster NGC 6752
Explanation: Some 13,000 light-years away toward the southern constellation Pavo, the globular star cluster NGC 6752 roams the halo of our Milky Way galaxy. Over 10 billion years old, NGC 6752 follows clusters Omega Centauri, 47 Tucanae, and Messier 22 as the fourth brightest globular in planet Earth's night sky. It holds over 100 thousand stars in a sphere about 100 light-years in diameter. Telescopic explorations of NGC 6752 have found that a remarkable fraction of the stars near the cluster's core are multiple star systems. They also reveal the presence of blue straggle stars, stars which appear to be too young and massive to exist in a cluster whose stars are all expected to be at least twice as old as the Sun. The blue stragglers are thought to be formed by star mergers and collisions in the dense stellar environment at the cluster's core. This sharp color composite also features the cluster's ancient red giant stars in yellowish hues. (Note: The bright, spiky blue star about 8 o'clock from the cluster center is a foreground star along the line-of-sight to NGC 6752)

APOD: 2024 October 23 – Caught
Explanation: What if a rocket could return to its launch tower -- and be caught? This happened for the first time 10 days ago, after a SpaceX Starship rocket blasted off from its pad in Boca Chica, Texas, USA. Starship then split, as planned, with its upper stage landing in the Pacific Ocean. The big difference was the lower stage, Super Heavy Booster 12, was caught by its launch tower about 7 minutes later. Catching a rocket for reuse is a new and innovative way to help reduce the cost of rocket flight by making rockets more easily reusable. Starship rockets may be used by NASA in the future to send spacecraft to Earth orbit, the Moon, and even other planets.

APOD: 2024 October 22 – M16: Pillars of Star Creation
Explanation: These dark pillars may look destructive, but they are creating stars. This pillar-capturing picture of the Eagle Nebula combines visible light exposures taken with the Hubble Space Telescope with infrared images taken with the James Webb Space Telescope to highlight evaporating gaseous globules (EGGs) emerging from pillars of molecular hydrogen gas and dust. The giant pillars are light years in length and are so dense that interior gas contracts gravitationally to form stars. At each pillar's end, the intense radiation of bright young stars causes low density material to boil away, leaving stellar nurseries of dense EGGs exposed. The Eagle Nebula, associated with the open star cluster M16, lies about 7000 light years away.

APOD: 2024 October 21 – Comet Tsuchinshan ATLAS over California
Explanation: The tails of Comet Tsuchinshan-ATLAS were a sight to behold. Pictured, C/2023 A3 (Tsuchinshan–ATLAS) was captured near peak impressiveness last week over the Eastern Sierra Mountains in California, USA. The comet not only showed a bright tail, but a distinct anti-tail pointing in nearly the opposite direction. The globular star cluster M5 can be seen on the right, far in the distance. As it approached, it was unclear if this crumbling iceberg would disintegrate completely as it warmed in the bright sunlight. In reality, the comet survived to become brighter than any star in the night (magnitude -4.9), but unfortunately was then so nearly in front of the Sun that it was hard for many casual observers to locate. Whether Comet Tsuchinshan-Atlas becomes known as the Great Comet of 2024 now depends, in part, on how impressive incoming comet C/2024 S1 (ATLAS) becomes over the next two weeks.

APOD: 2024 October 20 – Dark Matter in a Simulated Universe
Explanation: Is our universe haunted? It might look that way on this dark matter map. The gravity of unseen dark matter is the leading explanation for why galaxies rotate so fast, why galaxies orbit clusters so fast, why gravitational lenses so strongly deflect light, and why visible matter is distributed as it is both in the local universe and on the cosmic microwave background. The featured image from the American Museum of Natural History's Hayden Planetarium Space Show Dark Universe highlights one example of how pervasive dark matter might haunt our universe. In this frame from a detailed computer simulation, complex filaments of dark matter, shown in black, are strewn about the universe like spider webs, while the relatively rare clumps of familiar baryonic matter are colored orange. These simulations are good statistical matches to astronomical observations. In what is perhaps a scarier turn of events, dark matter -- although quite strange and in an unknown form -- is no longer thought to be the strangest source of gravity in the universe. That honor now falls to dark energy, a more uniform source of repulsive gravity that seems to now dominate the expansion of the entire universe.

APOD: 2024 October 19 - Comet Tsuchinshan ATLAS Flys Away
Explanation: These six panels follow daily apparitions of comet C/2023 A3 Tsuchinshan-ATLAS as it moved away from our fair planet during the past week. The images were taken with the same camera and lens at the indicated dates and locations from California, planet Earth. At far right on October 12 the visitor from the distant Oort cloud was near its closest approach, some 70 million kilometers (about 4 light-minutes) away. Its bright coma and long dust tail were close on the sky to the setting Sun but still easy to spot against a bright western horizon. Over the following days, the outbound comet steadily climbs above the ecliptic and north into the darker western evening sky, but begins to fade from view. Crossing the Earth's orbital plane around October 14, Tsuchinshan-ATLAS exhibits a noticeable antitail extended toward the western horizon. Higher in the evening sky at sunset by October 17 (far left) the comet has faded and reached a distance of around 77 million kilometers from planet Earth. Hopefully you enjoyed some of Tsuchinshan-ATLAS's bid to become the best comet of 2024. This comet's initial orbital period estimates were a mere 80,000 years, but in fact it may never return to the inner Solar System.

APOD: 2024 October 18 - Most of Comet Tsuchinshan ATLAS
Explanation: On October 14 it was hard to capture a full view of Comet C/2023 A3 Tsuchinshan-ATLAS. Taken after the comet's closest approach to our fair planet, this evening skyview almost does though. With two telephoto frames combined, the image stretches about 26 degrees across the sky from top to bottom, looking west from Gates Pass, Tucson, Arizona. Comet watchers that night could even identify globular star cluster M5 and the faint apparition of periodic comet 13P Olbers near the long the path of Tsuchinshan-ATLAS's whitish dust tail above the bright comet's coma. Due to perspective as the Earth is crossing the comet's orbital plane, Tsuchinshan-ATLAS also has a pronounced antitail. The antitail is composed of dust previously released and fanning out away from the Sun along the comet's orbit, visible as a needle-like extension below the bright coma toward the rugged western horizon.

APOD: 2024 October 17 - The Clipper and the Comet
Explanation: NASA's Europa Clipper is now headed toward an ocean world beyond Earth. The large spacecraft is tucked into the payload fairing atop the Falcon Heavy rocket in this photo, taken at Kennedy Space Center the day before the mission's successful October 14 launch. Europa Clipper's interplanetary voyage will first take it to Mars, then back to Earth, and then on to Jupiter on gravity assist trajectories that will allow it to enter orbit around Jupiter in April 2030. Once orbiting Jupiter, the spacecraft will fly past Europa 49 times, exploring a Jovian moon with a global subsurface ocean that may have conditions to support life. Posing in the background next to the floodlit rocket is Comet Tsuchinsan-ATLAS, about a day after the comet's closest approach to Earth. A current darling of evening skies, the naked-eye comet is a visitor from the distant Oort cloud

APOD: 2024 October 16 – Colorful Aurora over New Zealand
Explanation: Sometimes the night sky is full of surprises. Take the sky over Lindis Pass, South Island, New Zealand one-night last week. Instead of a typically calm night sky filled with constant stars, a busy and dynamic night sky appeared. Suddenly visible were pervasive red aurora, green picket-fence aurora, a red SAR arc, a STEVE, a meteor, and the Moon. These outshone the center of our Milky Way Galaxy and both of its two satellite galaxies: the LMC and SMC. All of these were captured together on 28 exposures in five minutes, from which this panorama was composed. Auroras lit up many skies last week, as a Coronal Mass Ejection from the Sun unleashed a burst of particles toward our Earth that created colorful skies over latitudes usually too far from the Earth's poles to see them. More generally, night skies this month have other surprises, showing not only auroras -- but comets.

APOD: 2024 October 15 – Animation: Comet Tsuchinshan ATLAS Tails Prediction
Explanation: How bright and strange will the tails of Comet Tsuchinshan-ATLAS become? The comet has brightened dramatically over the few weeks as it passed its closest to the Sun and, just three days ago, passed its closest to the Earth. C/2023 A3 (Tsuchinshan–ATLAS) became of the brightest comets of the past century over the past few days, but was unfortunately hard to see because it was so nearly superposed on the Sun. As the comet appears to move away from the Sun, it is becoming a remarkable sight -- but may soon begin to fade. The featured animated video shows how the comet's tails have developed, as viewed from Earth, and gives one prediction about how they might further develop. As shown in the video, heavier parts of the dust tail that trails the comet have begun to appear to point in nearly the opposite direction from lighter parts of the dust tail as well as the comet's ion tail, the blue tail that is pushed directly out from the Sun by the solar wind.

APOD: 2024 October 14 – Comet Tsuchinshan ATLAS Over the Lincoln Memorial
Explanation: Go outside at sunset tonight and see a comet! C/2023 A3 (Tsuchinshan–ATLAS) has become visible in the early evening sky in northern locations to the unaided eye. To see the comet, look west through a sky with a low horizon. If the sky is clear and dark enough, you will not even need binoculars -- the faint tail of the comet should be visible just above the horizon for about an hour. Pictured, Comet Tsuchinshan-ATLAS was captured two nights ago over the Lincoln Memorial monument in Washington, DC, USA. With each passing day at sunset, the comet and its changing tail should be higher and higher in the sky, although exactly how bright and how long its tails will be can only be guessed.

APOD: 2024 October 13 – Aurora Timelapse Over Italian Alps
Explanation: Did you see last night's aurora? This question was relevant around much of the world a few days ago because a powerful auroral storm became visible unusually far from the Earth's poles. The cause was a giant X-class solar flare on Tuesday that launched energetic electrons and protons into the Solar System, connecting to the Earth via our planet's magnetic field. A red glow of these particles striking oxygen atoms high in Earth's atmosphere pervades the frame, while vertical streaks dance. The featured video shows a one-hour timelapse as seen from Cortina d'Ampezzo over Alps Mountain peaks in northern Italy. Stars from our Milky Way Galaxy dot the background while streaks from airplanes and satellites punctuate the foreground. The high recent activity of our Sun is likely to continue to produce picturesque auroras over Earth during the next year or so.

APOD: 2024 October 12 - Northern Lights, West Virginia
Explanation: A gravel country lane gently winds through this colorful rural night skyscape. Captured from Monroe County in southern West Virginia on the evening of October 10, the starry sky above is a familiar sight. Shimmering curtains of aurora borealis or northern lights definitely do not make regular appearances here, though. Surprisingly vivid auroral displays were present on that night at very low latitudes around the globe, far from their usual northern and southern high latitude realms. The extensive auroral activity was evidence of a severe geomagnetic storm triggered by the impact of a coronal mass ejection (CME), an immense magnetized cloud of energetic plasma. The CME was launched toward Earth from the active Sun following a powerful X-class solar flare.

APOD: 2024 October 11 - Ring of Fire over Easter Island
Explanation: The second solar eclipse of 2024 began in the Pacific. On October 2nd the Moon's shadow swept from west to east, with an annular eclipse visible along a narrow antumbral shadow path tracking mostly over ocean, making its only major landfall near the southern tip of South America, and then ending in the southern Atlantic. The dramatic total annular eclipse phase is known to some as a ring of fire. Also tracking across islands in the southern Pacific, the Moon's antumbral shadow grazed Easter Island allowing denizens to follow all phases of the annular eclipse. Framed by palm tree leaves this clear island view is a stack of two images, one taken with and one taken without a solar filter near the moment of the maximum annular phase. The New Moon's silhouette appears just off center, though still engulfed by the bright disk of the active Sun.

APOD: 2024 October 10 - Five Bright Comets from SOHO
Explanation: Five bright comets are compared in these panels, recorded by a coronograph on board the long-lived, sun-staring SOHO spacecraft. Arranged chronologically all are recognizable by their tails streaming away from the Sun at the center of each field of view, where a direct view of the overwhelmingly bright Sun is blocked by the coronagraph's occulting disk. Each comet was memorable for earthbound skygazers, starting at top left with Comet McNaught, the 21st century's brightest comet (so far). C/2023 A3 Tsuchinshan-ATLAS, following its perihelion with the active Sun at bottom center, has most recently grabbed the attention of comet watchers around the globe. By the end of October 2024, the blank 6th panel may be filled with bright sungrazer comet C/2024 S1 (ATLAS). ... or not.

APOD: 2024 October 8 – Annular Eclipse over Patagonia
Explanation: Can you find the Sun? OK, but can you explain why there’s a big dark spot in the center? The spot is the Moon, and the impressive alignment shown, where the Moon lines up inside the Sun, is called an annular solar eclipse. Such an eclipse occurred just last week and was visible from a thin swath mostly in Earth's southern hemisphere. The featured image was captured from Patagonia, Chile. When the Moon is significantly closer to the Earth and it aligns with the Sun, a total solar eclipse is then visible from parts of the Earth. Annular eclipses are slightly more common than total eclipses, but as the Moon moves slowly away from the Earth, before a billion more years, the Moon's orbit will no longer bring it close enough for a total solar eclipse to be seen from anywhere on Earth.

APOD: 2024 October 7 – The Long Tails of Comet Tsuchinshan ATLAS
Explanation: A bright comet is moving into the evening skies. C/2023 A3 (Tsuchinshan–ATLAS) has brightened and even though it is now easily visible to the unaided eye, it is so near to the Sun that it is still difficult to see. Pictured, Comet Tsuchinshan–ATLAS was captured just before sunrise from an Andes Mountain in Peru. Braving cold weather, this unusually high perch gave the astrophotographer such a low eastern horizon that the comet was obvious in the pre-dawn sky. Visible in the featured image is not only an impressively long dust tail extending over many degrees, but an impressively long and blue ion tail, too.  This month, as the comet moves out from the Sun and passes the Earth, evening observers should be able to see the huge dirty ice ball toward the west just after sunset.

APOD: 2024 October 6 – The Magnificent Tail of Comet McNaught
Explanation: Comet McNaught, the Great Comet of 2007, grew a spectacularly long and filamentary tail. The magnificent tail spread across the sky and was visible for several days to Southern Hemisphere observers just after sunset. The amazing ion tail showed its greatest extent on long-duration, wide-angle camera exposures. During some times, just the tail itself was visible just above the horizon for many northern observers as well. Comet C/2006 P1 (McNaught), estimated to have attained a peak brightness of magnitude -5 (minus five), was caught by the comet's discoverer in the featured image just after sunset in January 2007 from Siding Spring Observatory in Australia. Comet McNaught, the brightest comet in decades, then faded as it moved further into southern skies and away from the Sun and Earth. Over the next month, Comet Tsuchinshan–ATLAS, a candidate for the Great Comet of 2024, should display its most spectacular tails visible from the Earth.

APOD: 2024 October 4 - Comet at Moonrise
Explanation: Comet C/2023 A3 (Tsuchinshan–ATLAS) is growing brighter in planet Earth's sky. Fondly known as comet A3, this new visitor to the inner Solar System is traveling from the distant Oort cloud. The comet reached perihelion, its closest approach to the Sun, on September 27 and will reach perigee, its closest to our fair planet, on October 12, by then becoming an evening sky apparition. But comet A3 was an early morning riser on September 30 when this image was made. Its bright coma and already long tail share a pre-dawn skyscape from Praia Grande, Santa Catarina in southern Brazil with the waning crescent Moon just peeking above the eastern horizon. While the behaviour of comets is notoriously unpredictable, Tsuchinshan–ATLAS could become a comet visually rivaling C/2020 F3 (NEOWISE). Comet NEOWISE wowed skygazers in the summer of 2020.

APOD: 2024 October 3 - Eclipse at Sunrise
Explanation: The second solar eclipse of 2024 began in the Pacific. On October 2nd the Moon's shadow swept from west to east, with an annular eclipse visible along a narrow antumbral shadow path tracking mostly over ocean, crossing land near the southern tip of South America, and ending in the southern Atlantic. The dramatic total annular eclipse phase is known to some as a ring of fire. Still, a partial eclipse of the Sun was experienced over a wide region. Captured at one of its earliest moments, October's eclipsed Sun is seen just above the clouds near sunrise in this snapshot. The partially eclipsed solar disk is close to the maximum eclipse as seen from Mauna Kea Observatory Visitor Center, Island of Hawaii, planet Earth.

APOD: 2024 October 1 – Porphyrion: The Longest Known Black Hole Jets
Explanation: How far can black hole jets extend? A new record was found just recently with the discovery of a 23-million light-year long jet pair from a black hole active billions of years ago. Dubbed Porphyrion for a mythological Greek giant, the impressive jets were created by a type of black hole that does not usually create long jets -- one that is busy creating radiation from infalling gas. The featured animated video depicts what it might look like to circle around this powerful black hole system. Porphyrion is shown as a fast stream of energetic particles, and the bright areas are where these particles are impacting surrounding gas. The discovery was made using data from the Keck and Mayall (DESI) optical observatories as well as LOFAR and the Giant Metrewave Radio Telescope. The existence of these jets demonstrates that black holes can affect not only their home galaxies but far out into the surrounding universe.

APOD: 2024 September 30 – Comet Tsuchinshan ATLAS over Mexico
Explanation: The new comet has passed its closest to the Sun and is now moving closer to the Earth. C/2023 A3 (Tsuchinshan–ATLAS) is currently moving out from inside the orbit of Venus and on track to pass its nearest to the Earth in about two weeks. Comet Tsuchinshan-ATLAS, pronounced "Choo-cheen-shahn At-less,", is near naked-eye visibility and easily picked up by long-exposure cameras. The comet can also now be found by observers in Earth's northern hemisphere as well as the south. The featured image was captured just a few days ago above Zacatecas, Mexico. Because clouds were obscuring much of the pre-dawn sky, the astrophotographer released a drone to take pictures from higher up, several of which were later merged to enhance the comet's visibility. Although the future brightness of comets is hard to predict, there is increasing hope that Comet Tsuchinshan-ATLAS will further brighten as it enters the early evening sky.

APOD: 2024 September 29 – Seven Dusty Sisters
Explanation: Is this really the famous Pleiades star cluster? Known for its iconic blue stars, the Pleiades is shown here in infrared light where the surrounding dust outshines the stars. Here, three infrared colors have been mapped into visual colors (R=24, G=12, B=4.6 microns). The base images were taken by NASA's orbiting Wide Field Infrared Survey Explorer (WISE) spacecraft. Cataloged as M45 and nicknamed the Seven Sisters, the Pleiades star cluster is by chance situated in a passing dust cloud. The light and winds from the massive Pleiades stars preferentially repel smaller dust particles, causing the dust to become stratified into filaments, as seen. The featured image spans about 20 light years at the distance of the Pleiades, which lies about 450 light years distant toward the constellation of the Bull (Taurus).

APOD: 2024 September 28 - Rocket Eclipse at Sunset
Explanation: Shockwaves ripple across the glare as a launch eclipses the setting Sun in this exciting close-up. Captured on September 17, the roaring Falcon 9 rocket carried European Galileo L13 navigation satellites to medium Earth orbit after a lift-off from Cape Canaveral on Florida's space coast. The Falcon 9 booster returned safely to Earth about 8.5 minutes later, notching the 22nd launch and landing for the reusable workhorse launch vehicle. But where did it land? Just Read the Instructions.

APOD: 2024 September 26 - The Great Globular Cluster in Hercules
Explanation: In 1716, English astronomer Edmond Halley noted, "This is but a little Patch, but it shows itself to the naked Eye, when the Sky is serene and the Moon absent." Of course, M13 is now less modestly recognized as the Great Globular Cluster in Hercules, one of the brightest globular star clusters in the northern sky. Sharp telescopic views like this one reveal the spectacular cluster's hundreds of thousands of stars. At a distance of 25,000 light-years, the cluster stars crowd into a region 150 light-years in diameter. Approaching the cluster core, upwards of 100 stars could be contained in a cube just 3 light-years on a side. For comparison, the closest star to the Sun is over 4 light-years away. The deep, wide-field image also reveals distant background galaxies including NGC 6207 at the upper left, and faint, foreground Milky Way dust clouds known to some as integrated flux nebulae.

APOD: 2024 September 25 – Comet A3 Through an Australian Sunrise
Explanation: Comet Tsuchinshan-ATLAS is now visible in the early morning sky. Diving into the inner Solar System at an odd angle, this large dirty iceberg will pass its closest to the Sun -- between the orbits of Mercury and Venus -- in just two days. Long camera exposures are now capturing C/2023 A3 (Tsuchinshan–ATLAS), sometimes abbreviated as just A3, and its dust tail before and during sunrise. The featured image composite was taken four days ago and captured the comet as it rose above Lake George, NSW, Australia. Vertical bands further left are images of the comet as the rising Sun made the predawn sky increasingly bright and colorful. Just how bright the comet will become over the next month is currently unknown as it involves how much gas and dust the comet's nucleus will expel. Optimistic skywatchers are hoping for a great show where Tsuchinshan–ATLAS creates dust and ion tails visible across Earth's sky and becomes known as the Great Comet of 2024.

APOD: 2024 September 21 - Sunrise Shadows in the Sky
Explanation: The defining astronomical moment of this September's equinox is at 12:44 UTC on September 22, when the Sun crosses the celestial equator moving south in its yearly journey through planet Earth's sky. That marks the beginning of fall for our fair planet in the northern hemisphere and spring in the southern hemisphere, when day and night are nearly equal around the globe. Of course, if you celebrate the astronomical change of seasons by watching a sunrise you can also look for crepuscular rays. Outlined by shadows cast by clouds, crepuscular rays can have a dramatic appearance in the twilight sky during any sunrise (or sunset). Due to perspective, the parallel cloud shadows will seem to point back to the rising Sun and a place due east on your horizon on the equinox date. But in this spectacular sunrise skyscape captured in early June, the parallel shadows and crepuscular rays appear to converge toward an eastern horizon's more northerly sunrise. The well-composed photo places the rising Sun just behind the bell tower of a church in the town of Vic, province of Barcelona, Catalonia, Spain.

APOD: 2024 September 20 - A Hazy Harvest Moon
Explanation: For northern hemisphere dwellers, September's Full Moon was the Harvest Moon. On September 17/18 the sunlit lunar nearside passed into shadow, just grazing Earth's umbra, the planet's dark, central shadow cone, in a partial lunar eclipse. Over the two and a half hours before dawn a camera fixed to a tripod was used to record this series of exposures as the eclipsed Harvest Moon set behind Spiš Castle in the hazy morning sky over eastern Slovakia. Famed in festival, story, and song, Harvest Moon is just the traditional name of the full moon nearest the autumnal equinox. According to lore the name is a fitting one. Despite the diminishing daylight hours as the growing season drew to a close, farmers could harvest crops by the light of a full moon shining on from dusk to dawn. This September's Harvest Moon was also known to some as a supermoon, a term becoming a traditional name for a full moon near perigee.

APOD: 2024 September 18 – The Mermaid Nebula Supernova Remnant
Explanation: New stars are born from the remnants of dead stars. The gaseous remnant of the gravitational collapse and subsequent death of a very massive star in our Milky Way created the G296.5+10.0 supernova remnant, of which the featured Mermaid Nebula is part. Also known as the Betta Fish Nebula, the Mermaid Nebula makes up part of an unusual subclass of supernova remnants that are two-sided and nearly circular. Originally discovered in X-rays, the filamentary nebula is a frequently studied source also in radio and gamma-ray light. The blue color visible here originates from doubly ionized oxygen (OIII), while the deep red is emitted by hydrogen gas. The nebula's mermaid-like shape has proven to be useful for measurements of the interstellar magnetic field.

APOD: 2024 September 15 – Find the Man in the Moon
Explanation: Have you ever seen the Man in the Moon? This common question plays on the ability of humans to see pareidolia -- imagining familiar icons where they don't actually exist. The textured surface of Earth's full Moon is home to numerous identifications of iconic objects, not only in modern western culture but in world folklore throughout history. Examples, typically dependent on the Moon's perceived orientation, include the Woman in the Moon and the Rabbit in the Moon. One facial outline commonly identified as the Man in the Moon starts by imagining the two dark circular areas -- lunar maria -- here just above the Moon's center, to be the eyes. Surprisingly, there actually is a man in this Moon image -- a close look will reveal a real person -- with a telescope -- silhouetted against the Moon. This well-planned image was taken in 2016 in Cadalso de los Vidrios in Madrid, Spain.

APOD: 2024 September 12 - Young Star Cluster NGC 1333
Explanation: This spectacular mosaic of images from the James Webb Space Telescope peers into the heart of young star cluster NGC 1333. A mere 1,000 light-years distant toward the heroic constellation Perseus, the nearby star cluster lies at the edge of the large Perseus molecular cloud. Part of Webb's deep exploration of the region to identify low mass brown dwarf stars and free floating planets, the space telescope's combined field of view spans nearly 2 light-years across the dusty cluster's turbulent stellar nursery. In fact, NGC 1333 is known to harbor stars less than a million years old, though most are hidden from optical telescopes by the pervasive stardust. The chaotic environment may be similar to one in which our own Sun formed over 4.5 billion years ago.

APOD: 2024 September 10 – Horsehead and Orion Nebulas
Explanation: The dark Horsehead Nebula and the glowing Orion Nebula are contrasting cosmic vistas. Adrift 1,500 light-years away in one of the night sky's most recognizable constellations, they appear in opposite corners of the above stunning mosaic. The familiar Horsehead nebula appears as a dark cloud, a small silhouette notched against the long glow of hydrogen -- here shown in gold -- at the lower left. Alnitak is the easternmost star in Orion's belt and is seen as the bright star to the left of the Horsehead. Just below Alnitak is the Flame Nebula, with clouds of bright emission and dramatic dark dust lanes. The magnificent emission region, the Orion Nebula (aka M42), lies at the upper right. Immediately to its left is a prominent reflection nebula sometimes called the Running Man. Pervasive tendrils of glowing hydrogen gas are easily traced throughout the region.

APOD: 2024 September 9 – Mars: Moon, Craters, and Volcanos
Explanation: If you could fly over Mars, what might you see? The featured image shows exactly this in the form of a Mars Express vista captured over a particularly interesting region on Mars in July. The picture's most famous feature is Olympus Mons, the largest volcano in the Solar System, visible on the upper right. Another large Martian volcano is visible on the right horizon: Pavonis Mons. Several circular impact craters can be seen on the surface of the aptly named red planet. Impressively, this image was timed to capture the dark and doomed Martian moon Phobos, visible just left of center. The surface feature on the lower left, known as Orcus Patera, is unusual for its large size and oblong shape, and mysterious because the processes that created it still remain unknown. ESA's robotic Mars Express spacecraft was launched in 2003 and, among many notable science discoveries, bolstered evidence that Mars was once home to large bodies of water.

APOD: 2024 September 8 – M31: The Andromeda Galaxy
Explanation: The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy. Even at some two and a half million light-years distant, this immense spiral galaxy -- spanning over 200,000 light years -- is visible, although as a faint, nebulous cloud in the constellation Andromeda. A bright yellow nucleus, dark winding dust lanes, and expansive spiral arms dotted with blue star clusters and red nebulae, are recorded in this stunning telescopic image which combines data from orbiting Hubble with ground-based images from Subaru and Mayall. In only about 5 billion years, the Andromeda galaxy may be even easier to see -- as it will likely span the entire night sky -- just before it merges with, or passes right by, our Milky Way Galaxy.

APOD: 2024 September 7 - Small Moon Deimos
Explanation: Mars has two tiny moons, Phobos and Deimos, named for the figures in Greek mythology Fear and Panic. Detailed surface views of smaller moon Deimos are shown in both these panels. The images were taken in 2009, by the HiRISE camera on board the Mars Reconnaissance Orbiter spacecraft, NASA's long-lived interplanetary internet satellite. The outermost of the two Martian moons, Deimos is one of the smallest known moons in the Solar System, measuring only about 15 kilometers across. Both Martian moons were discovered in 1877 by Asaph Hall, an American astronomer working at the US Naval Observatory in Washington D.C. But their existence was postulated around 1610 by Johannes Kepler, the astronomer who derived the laws of planetary motion. In this case, Kepler's prediction was not based on scientific principles, but his writings and ideas were so influential that the two Martian moons are discussed in works of fiction such as Jonathan Swift's Gulliver's Travels, written in 1726, over 150 years before their discovery.

APOD: 2024 September 6 - Ringed Ice Giant Neptune
Explanation: Ringed ice giant Neptune lies near the center of this sharp near-infrared image from the James Webb Space Telescope. The dim and distant world is the farthest planet from the Sun, about 30 times farther away than planet Earth. But in the stunning Webb view, the planet's dark and ghostly appearance is due to atmospheric methane that absorbs infrared light. High altitude clouds that reach above most of Neptune's absorbing methane easily stand out in the image though. Coated with frozen nitrogen, Neptune's largest moon Triton is brighter than Neptune in reflected sunlight, seen at the upper left sporting the Webb telescope's characteristic diffraction spikes. Including Triton, seven of Neptune's 14 known moons can be identified in the field of view. Neptune's faint rings are striking in this space-based planetary portrait. Details of the complex ring system are seen here for the first time since Neptune was visited by the Voyager 2 spacecraft in August 1989.

APOD: 2024 September 5 - NGC 247 and Friends
Explanation: About 70,000 light-years across, NGC 247 is a spiral galaxy smaller than our Milky Way. Measured to be only 11 million light-years distant it is nearby though. Tilted nearly edge-on as seen from our perspective, it dominates this telescopic field of view toward the southern constellation Cetus. The pronounced void on one side of the galaxy's disk recalls for some its popular name, the Needle's Eye galaxy. Many background galaxies are visible in this sharp galaxy portrait, including the remarkable string of four galaxies just below and left of NGC 247 known as Burbidge's Chain. Burbidge's Chain galaxies are about 300 million light-years distant. NGC 247 itself is part of the Sculptor Group of galaxies along with shiny spiral NGC 253.

APOD: 2024 September 4 – NGC 6995: The Bat Nebula
Explanation: Can you see the bat? It haunts this cosmic close-up of the eastern Veil Nebula. The Veil Nebula itself is a large supernova remnant, the expanding debris cloud from the death explosion of a massive star. While the Veil is roughly circular in shape and covers nearly 3 degrees on the sky toward the constellation of the Swan (Cygnus), NGC 6995, known informally as the Bat Nebula, spans only 1/2 degree, about the apparent size of the Moon. That translates to 12 light-years at the Veil's estimated distance, a reassuring 1,400 light-years from planet Earth. In the composite of image data recorded through narrow band filters, emission from hydrogen atoms in the remnant is shown in red with strong emission from oxygen atoms shown in hues of blue. Of course, in the western part of the Veil lies another seasonal apparition: the Witch's Broom Nebula.

APOD: 2024 September 1 – The Moon Dressed Like Saturn
Explanation: Why does Saturn appear so big? It doesn't -- what is pictured are foreground clouds on Earth crossing in front of the Moon. The Moon shows a slight crescent phase with most of its surface visible by reflected Earthlight, known as Da Vinci glow. The Sun directly illuminates the brightly lit lunar crescent from the bottom, which means that the Sun must be below the horizon and so the image was taken before sunrise. This double take-inducing picture was captured on 2019 December 24, two days before the Moon slid in front of the Sun to create a solar eclipse. In the foreground, lights from small Guatemalan towns are visible behind the huge volcano Pacaya.

APOD: 2024 August 31 - IFN and the NGC 7771 Group
Explanation: Galaxies of the NGC 7771 Group are featured in this intriguing skyscape. Some 200 million light-years distant toward the constellation Pegasus, NGC 7771 is the large, edge-on spiral near center, about 75,000 light-years across, with two smaller galaxies below it. Large spiral NGC 7769 is seen face-on to the right. Galaxies of the NGC 7771 group are interacting, making repeated close passages that will ultimately result in galaxy-galaxy mergers on a cosmic timescale. The interactions can be traced by distortions in the shape of the galaxies themselves and faint streams of stars created by their mutual gravitational tides. But a clear view of this galaxy group is difficult to come by as the deep image also reveals extensive clouds of foreground dust sweeping across the field of view. The dim, dusty galactic cirrus clouds are known as Integrated Flux Nebulae. The faint IFN reflect starlight from our own Milky Way Galaxy and lie only a few hundred light-years above the galactic plane.

APOD: 2024 August 29 - Star Factory Messier 17
Explanation: A nearby star factory known as Messier 17 lies some 5,500 light-years away in the nebula-rich constellation Sagittarius. At that distance, this 1.5 degree wide field-of-view would span about 150 light-years. In the sharp color composite image faint details of the region's gas and dust clouds are highlighted with narrowband image data against a backdrop of central Milky Way stars. The stellar winds and energetic radiation from hot, massive stars already formed from M17's stock of cosmic gas and dust have slowly carved away at the remaining interstellar material, producing the nebula's cavernous appearance and the undulating shapes within. A popular stop on telescopic tours of the cosmos, M17 is also known as the Omega or the Swan Nebula.

APOD: 2024 August 27 – Moon Eclipses Saturn
Explanation: What if Saturn disappeared? Sometimes, it does. It doesn't really go away, though, it just disappears from view when our Moon moves in front. Such a Saturnian eclipse, more formally called an occultation, was visible along a long swath of Earth -- from Peru, across the Atlantic Ocean, to Italy -- only a few days ago. The featured color image is a digital fusion of the clearest images captured during the event and rebalanced for color and relative brightness between the relatively dim Saturn and the comparatively bright Moon. Saturn and the comparative bright Moon. The exposures were all taken from Breda, Catalonia, Spain, just before occultation. Eclipses of Saturn by our Moon will occur each month for the rest of this year. Each time, though, the fleeting event will be visible only to those with clear skies -- and the right location on Earth.

APOD: 2024 August 26 – Perseid Meteors Over Inner Mongolia
Explanation: Did you see it? One of the more common questions during a meteor shower occurs because the time it takes for a meteor to flash is similar to the time it takes for a head to turn. Possibly, though, the glory of seeing bright meteors shoot across the sky -- while knowing that they were once small pebbles on another world -- might make it all worthwhile, even if your observing partner(s) can't always share in your experience. The featured video is composed of short clips taken in Inner Mongolia, China during the 2023 Perseid Meteor Shower. Several bright meteors were captured while live-reaction audio was being recorded -- just as the meteors flashed. This year's 2024 Perseids also produced many beautiful meteors. Another good meteor shower to watch for is the Geminids which peak yearly in mid-December, this year with relatively little competing glow from a nearly new Moon.

APOD: 2024 August 24 - South Pacific Shadowset
Explanation: The full Moon and Earth's shadow set together in this island skyscape. The alluring scene was captured Tuesday morning, August 20, from Fiji, South Pacific Ocean, planet Earth. For early morning risers shadowset in the western sky is a daily apparition. Still, the grey-blue shadow is often overlooked in favor of a brighter eastern horizon. Extending through the dense atmosphere, Earth's setting shadow is bounded above by a pinkish glow or anti-twilight arch. Known as the Belt of Venus, the arch's lovely color is due to backscattering of reddened light from the opposite horizon's rising Sun. Of course, the setting Moon's light is reddened by the long sight-line through the atmosphere. But on that date the full Moon could be called a seasonal Blue Moon, the third full Moon in a season with four full Moons. And even though the full Moon is always impressive near the horizon, August's full Moon is considered by some the first of four consecutive full Supermoons in 2024.

APOD: 2024 August 22 - The Dark Tower in Scorpius
Explanation: In silhouette against a crowded star field along the tail of the arachnological constellation Scorpius, this dusty cosmic cloud evokes for some the image of an ominous dark tower. In fact, monstrous clumps of dust and molecular gas collapsing to form stars may well lurk within the dark nebula, a structure that spans almost 40 light-years across this gorgeous telescopic portrait. A cometary globule, the swept-back cloud is shaped by intense ultraviolet radiation from the OB association of very hot stars in NGC 6231, off the upper right corner of the scene. That energetic ultraviolet light also powers the globule's bordering reddish glow of hydrogen gas. Hot stars embedded in the dust can be seen as bluish reflection nebulae. This dark tower and associated nebulae are about 5,000 light-years away.

APOD: 2024 August 17 - Sky Full of Arcs
Explanation: On August 11 a Rocket Lab Electron rocket launched from a rotating planet. With a small satellite on board its mission was dubbed A Sky Full of SARs (Synthetic Aperture Radar satellites), departing for low Earth orbit from Mahia Peninsula on New Zealand's north island. The fiery trace of the Electron's graceful launch arc is toward the east in this southern sea and skyscape, a composite of 50 consecutive frames taken over 2.5 hours. Fixed to a tripod, the camera was pointing directly at the South Celestial Pole, the extension of planet Earth's axis of rotation in to space. But no bright star marks that location in the southern hemisphere's night sky. Still, the South Celestial Pole is easy to spot. It lies at the center of the concentric star trail arcs that fill the skyward field of view.

APOD: 2024 August 16 - Meteor Borealis
Explanation: A single exposure made with a camera pointed almost due north on August 12 recorded this bright Perseid meteor in the night sky west of Halifax, Nova Scotia, Canada. The meteor's incandescent trace is fleeting. It appears to cross the stars of the Big Dipper, famous northern asterism and celestial kitchen utensil, while shimmering curtains of aurora borealis, also known as the northern lights, dance in the night. Doubling the wow factor for night skywatchers near the peak of this year's Perseid meteor shower auroral activity on planet Earth was enhanced by geomagnetic storms. The intense space weather was triggered by flares from an active Sun.

APOD: 2024 August 15 - Late Night Vallentuna
Explanation: Bright Mars and even brighter Jupiter are in close conjunction just above the pine trees in this post-midnight skyscape from Vallentuna, Sweden. Taken on August 12 during a geomagnetic storm, the snapshot records the glow of aurora borealis or northern lights, beaming from the left side of the frame. Of course on that date Perseid meteors rained through planet Earth's skies, grains of dust from the shower's parent, periodic comet Swift-Tuttle. The meteor streak at the upper right is a Perseid plowing through the atmosphere at about 60 kilometers per second. Also well-known in Earth's night sky, the bright Pleiades star cluster shines below the Perseid meteor streak. In Greek myth, the Pleiades were seven daughters of the astronomical titan Atlas and sea-nymph Pleione. The Pleiades and their parents' names are given to the cluster's nine brightest stars.

APOD: 2024 August 14 – Meteors and Aurora over Germany
Explanation: This was an unusual night. For one thing, the night sky of August 11 and 12, earlier this week, occurred near the peak of the annual Perseid Meteor Shower. Therefore, meteors streaked across the dark night as small bits cast off from Comet Swift-Tuttle came crashing into the Earth's atmosphere. Even more unusually, for central Germany at least, the night sky glowed purple. The red-blue hue was due to aurora caused by an explosion of particles from the Sun a few days before. This auroral storm was so intense that it was seen as far south as Texas and Italy, in Earth's northern hemisphere. The featured image composite was built from 7 exposures taken over 26 minutes from Ense, Germany. The Perseids occur predictably every August, but auroras visible this far south are more unusual and less predictable.

APOD: 2024 August 13 – Giant Jet from the International Space Station
Explanation: What's that on the horizon? When circling the Earth on the International Space Station early last month, astronaut Matthew Dominick saw an unusual type of lightning just beyond the Earth's edge: a gigantic jet. The powerful jet appears on the left of the featured image in red and blue. Giant jet lightning has only been known about for the past 23 years. The atmospheric jets are associated with thunderstorms and extend upwards towards Earth's ionosphere. The lower part of the frame shows the Earth at night, with Earth's thin atmosphere tinted green from airglow. City lights are visible, sometimes resolved, but usually creating diffuse white glows in intervening clouds. The top of the frame reveals distant stars in the dark night sky. The nature of gigantic jets and their possible association with other types of Transient Luminous Events (TLEs) such as blue jets and red sprites remains an active topic of research.

APOD: 2024 August 11 – Animation: Perseid Meteor Shower
Explanation: Where do Perseid meteors come from? Mostly small bits of stony grit, Perseid meteoroids were once expelled from Comet Swift-Tuttle and continue to follow this comet's orbit as they slowly disperse. The featured animation depicts the entire meteoroid stream as it orbits our Sun. When the Earth nears this stream, as it does every year, the Perseid Meteor Shower occurs. Highlighted as bright in the animation, comet debris this size is usually so dim it is practically undetectable. Only a small fraction of this debris will enter the Earth's atmosphere, heat up and disintegrate brightly. Tonight and the next few nights promise some of the better skies to view the Perseid shower as well as other active showers because the first quarter moon will be absent from the sky from midnight onward.

APOD: 2024 August 9 - A Perseid Below
Explanation: Denizens of planet Earth typically watch meteor showers by looking up. But this remarkable view, captured on August 13, 2011 by astronaut Ron Garan, caught a Perseid meteor by looking down. From Garan's perspective on board the International Space Station orbiting at an altitude of about 380 kilometers, the Perseid meteors streak below, swept up dust from comet Swift-Tuttle. The vaporizing comet dust grains are traveling at about 60 kilometers per second through the denser atmosphere around 100 kilometers above Earth's surface. In this case, the foreshortened meteor flash is near frame center, below the curving limb of the Earth and a layer of greenish airglow, just below bright star Arcturus. Want to look up at a meteor shower? You're in luck, as the 2024 Perseid meteor shower is active now and predicted to peak near August 12. With interfering bright moonlight absent, this year you'll likely see many Perseid meteors under clear, dark skies after midnight.

APOD: 2024 August 7 – Milky Way Behind Three Merlons
Explanation: To some, they look like battlements, here protecting us against the center of the Milky Way. The Three Merlons, also called the Three Peaks of Lavaredo, stand tall today because they are made of dense dolomite rock which has better resisted erosion than surrounding softer rock. They formed about 250 million years ago and so are comparable in age with one of the great extinctions of life on Earth. A leading hypothesis is that this great extinction was triggered by an asteroid about 10-km across, larger in size than Mount Everest, impacting the Earth. Humans have gazed up at the stars in the Milky Way and beyond for centuries, making these battlefield-like formations, based in the Sexten Dolomites, a popular place for current and ancient astronomers.

APOD: 2024 August 4 – Gaia: Here Comes the Sun
Explanation: What would it look like to return home from outside our galaxy? Although designed to answer greater questions, data from ESA's robotic Gaia mission is helping to provide a uniquely modern perspective on humanity's place in the universe. Gaia orbits the Sun near the Earth and resolves stars' positions so precisely that it can determine a slight shift from its changing vantage point over the course of a year, a shift that is proportionately smaller for more distant stars -- and so determines distance. In the first sequence of the video, an illustration of the Milky Way is shown that soon resolves into a three-dimensional visualization of Gaia star data. A few notable stars are labelled with their common names, while others stars are labelled with numbers from a Gaia catalog. Eventually, the viewer arrives in our stellar neighborhood where many stars were tracked by Gaia, and soon at our home star Sol, the Sun. At the video's end, the reflective glow of Sol's third planet becomes visible: Earth.

APOD: 2024 August 3 - Glory and Fog Bow
Explanation: On a road trip up Mount Uludağ in Bursa province, Turkey these motorcyclists found themselves above low clouds and fog in late June. With the bright Sun directly behind them, the view down the side of the great mountain revealed a beautiful, atmospheric glory and fog bow. Known to some as the heiligenschein or the Specter of the Brocken, a glory can also sometimes be seen from airplanes or even high buildings. It often appears to be a dark giant surrounded by a bright halo. Of course the dark giant is just the shadow of the observer (90MB video) cast opposite the Sun. The clouds and fog are composed of very small water droplets, smaller than rain drops, that refract and reflect sunlight to create the glory's colorful halo and this more extensive fog bow.

APOD: 2024 August 2 - Mars Passing By
Explanation: As Mars wanders through Earth's night, it passes about 5 degrees south of the Pleiades star cluster in this composite astrophoto. The skyview was constructed from a series of images captured over a run of 16 consecutive clear nights beginning on July 12. Mars' march across the field of view begins at the far right, the planet's ruddy hue showing a nice contrast with the blue Pleiades stars. Moving much faster across the sky against the distant stars, the fourth planet from the Sun easily passes seventh planet Uranus. Red planet Mars and the ice giant world were in close conjunction, about 1/2 degree apart, on July 16. Continuing its rapid eastward trek, Mars has now left the sister stars and outer planet behind though, passing north of red giant star Aldebaran. Mars will come within about 1/3 degree of Jupiter in planet Earth's sky on August 14.

APOD: 2024 July 29 – Milky Way over Uluru
Explanation: What's happening above Uluru? A United Nations World Heritage Site, Uluru is an extraordinary 350-meter high mountain in central Australia that rises sharply from nearly flat surroundings. Composed of sandstone, Uluru has slowly formed over the past 300 million years as softer rock eroded away. The Uluru region has been a home to humans for over 22,000 years. Recorded last month, the starry sky above Uluru includes the central band of our Milky Way galaxy, complete with complex dark filaments of dust, bright red emission nebulas, and billions of stars.

APOD: 2024 July 28 – Sun Dance
Explanation: Sometimes, the surface of our Sun seems to dance. In the middle of 2012, for example, NASA's Sun-orbiting Solar Dynamic Observatory spacecraft imaged an impressive prominence that seemed to perform a running dive roll like an acrobatic dancer. The dramatic explosion was captured in ultraviolet light in the featured time-lapse video covering about three hours. A looping magnetic field directed the flow of hot plasma on the Sun. The scale of the dancing prominence is huge -- the entire Earth would easily fit under the flowing arch of hot gas. A quiescent prominence typically lasts about a month and may erupt in a Coronal Mass Ejection (CME), expelling hot gas into the Solar System. The energy mechanism that creates a solar prominence is still a topic of research. Like in 2012, this year the Sun's surface is again quite active and features many filaments and prominences.

APOD: 2024 July 26 - Facing NGC 6946
Explanation: From our vantage point in the Milky Way Galaxy, we see NGC 6946 face-on. The big, beautiful spiral galaxy is located just 20 million light-years away, behind a veil of foreground dust and stars in the high and far-off constellation Cepheus. In this sharp telescopic portrait, from the core outward the galaxy's colors change from the yellowish light of old stars in the center to young blue star clusters and reddish star forming regions along the loose, fragmented spiral arms. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, since the early 20th century ten confirmed supernovae, the death explosions of massive stars, were discovered in NGC 6946. Nearly 40,000 light-years across, NGC 6946 is also known as the Fireworks Galaxy.

APOD: 2024 July 22 – Chamaeleon Dark Nebulas
Explanation: Sometimes the dark dust of interstellar space has an angular elegance. Such is the case toward the far-south constellation of Chamaeleon. Normally too faint to see, dark dust is best known for blocking visible light from stars and galaxies behind it. In this 36.6-hour exposure, however, the dust is seen mostly in light of its own, with its strong red and near-infrared colors creating a brown hue. Contrastingly blue, the bright star Beta Chamaeleontis is visible on the upper right, with the dust that surrounds it preferentially reflecting blue light from its primarily blue-white color. All of the pictured stars and dust occur in our own Milky Way Galaxy with one notable exception: the white spot just below Beta Chamaeleontis is the galaxy IC 3104 which lies far in the distance. Interstellar dust is mostly created in the cool atmospheres of giant stars and dispersed into space by stellar light, stellar winds, and stellar explosions such as supernovas.

APOD: 2024 July 19 - Anticrepuscular Rays at the Planet Festival
Explanation: For some, these subtle bands of light and shadow stretched across the sky as the Sun set on July 11. Known as anticrepuscular rays, the bands are formed as a large cloud bank near the western horizon cast long shadows through the atmosphere at sunset. Due to the camera's perspective, the bands of light and shadow seem to converge toward the eastern (opposite) horizon at a point seen just above a 14th century hilltop castle in Brno, Czech Republic. In the foreground, denizens of planet Earth are enjoying the region's annual Planet Festival in the park below the Brno Observatory and Planetarium. And while crepuscular and anticrepuscular rays are a relatively common atmospheric phenomenon, this festival's 10 meter diameter inflatable spheres representing bodies of the Solar System are less often seen on planet Earth.

APOD: 2024 July 15 – The Tadpole Galaxy from Hubble
Explanation: Why does this galaxy have such a long tail? In this stunning vista, based on image data from the Hubble Legacy Archive, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation of the Dragon (Draco). Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from right to left in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper right. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.

APOD: 2024 July 14 – Meteor Misses Galaxy
Explanation: The galaxy was never in danger. For one thing, the Triangulum galaxy (M33), pictured, is much bigger than the tiny grain of rock at the head of the meteor. For another, the galaxy is much farther away -- in this instance 3 million light years as opposed to only about 0.0003 light seconds. Even so, the meteor's path took it angularly below the galaxy. Also the wind high in Earth's atmosphere blew the meteor's glowing evaporative molecule train away from the galaxy, in angular projection. Still, the astrophotographer was quite lucky to capture both a meteor and a galaxy in a single exposure -- which was subsequently added to two other images of M33 to bring up the spiral galaxy's colors. At the end, the meteor was gone in a second, but the galaxy will last billions of years.

APOD: 2024 July 13 - Solar System Family Portrait
Explanation: In 1990, cruising four billion miles from the Sun, the Voyager 1 spacecraft looked back to make this first ever Solar System family portrait. The complete portrait is a 60 frame mosaic made from a vantage point 32 degrees above the ecliptic plane. In it, Voyager's wide-angle camera frames sweep through the inner Solar System at the left, linking up with ice giant Neptune, the Solar System's outermost planet, at the far right. Positions for Venus, Earth, Jupiter, Saturn, Uranus, and Neptune are indicated by letters, while the Sun is the bright spot near the center of the circle of frames. The inset frames for each of the planets are from Voyager's narrow-field camera. Unseen in the portrait are Mercury, too close to the Sun to be detected, and Mars, unfortunately hidden by sunlight scattered in the camera's optical system. Closer to the Sun than Neptune at the time, small, faint Pluto's position was not covered. In 2024 Voyager 1, NASA’s longest-running and most-distant spacecraft, is some 15 billion miles away, operating in interstellar space.

APOD: 2024 July 12 - Jones Emberson 1
Explanation: Planetary nebula Jones-Emberson 1 is the death shroud of a dying Sun-like star. It lies some 1,600 light-years from Earth toward the sharp-eyed constellation Lynx. About 4 light-years across, the expanding remnant of the dying star's atmosphere was shrugged off into interstellar space, as the star's central supply of hydrogen and then helium for fusion was depleted after billions of years. Visible near the center of the planetary nebula is what remains of the stellar core, a blue-hot white dwarf star. Also known as PK 164 +31.1, the nebula is faint and very difficult to glimpse at a telescope's eyepiece. But this deep image combining over 12 hours of exposure time does show it off in exceptional detail. Stars within our own Milky Way galaxy as well as background galaxies across the universe are scattered through the clear field of view. Ephemeral on the cosmic stage, Jones-Emberson 1 will fade away over the next few thousand years. Its hot, central white dwarf star will take billions of years to cool.

APOD: 2024 July 9 – Noctilucent Clouds over Florida
Explanation: These clouds are doubly unusual. First, they are rare noctilucent clouds, meaning that they are visible at night -- but only just before sunrise or just after sunset. Second, the source of these noctilucent clouds is actually known. In this rare case, the source of the sunlight-reflecting ice-crystals in the upper atmosphere can be traced back to the launch of a nearby SpaceX rocket about 30 minutes earlier. Known more formally as polar mesospheric clouds, the vertex of these icy wisps happens to converge just in front of a rising crescent Moon. The featured image -- and accompanying video -- were captured over Orlando, Florida, USA about a week ago. The bright spot to the right of the Moon is the planet Jupiter, while the dotted lights above the horizon on the right are from an airplane.

APOD: 2024 July 8 – Exoplanet Zoo: Other Stars
Explanation: Do other stars have planets like our Sun? Surely they do, and evidence includes slight star wobbles created by the gravity of orbiting exoplanets and slight star dimmings caused by orbiting planets moving in front. In all, there have now been over 5,500 exoplanets discovered, including thousands by NASA's space-based Kepler and TESS missions, and over 100 by ESO's ground-based HARPS instrument. Featured here is an illustrated guess as to what some of these exoplanets might look like. Neptune-type planets occupy the middle and are colored blue because of blue-scattering atmospheric methane they might contain. On the sides of the illustration, Jupiter-type planets are shown, colored tan and red from the scatterings of atmospheric gases that likely include small amounts of carbon. Interspersed are many Earth-type rocky planets of many colors. As more exoplanets are discovered and investigated, humanity is developing a better understanding of how common Earth-like planets are, and how common life might be in the universe.

APOD: 2024 July 7 – Iridescent Clouds over Sweden
Explanation: Why are these clouds multi-colored? A relatively rare phenomenon in clouds known as iridescence can bring up unusual colors vividly -- or even a whole spectrum of colors simultaneously. These polar stratospheric clouds also, known as nacreous and mother-of-pearl clouds, are formed of small water droplets of nearly uniform size. When the Sun is in the right position and, typically, hidden from direct view, these thin clouds can be seen significantly diffracting sunlight in a nearly coherent manner, with different colors being deflected by different amounts. Therefore, different colors will come to the observer from slightly different directions. Many clouds start with uniform regions that could show iridescence but quickly become too thick, too mixed, or too angularly far from the Sun to exhibit striking colors. The featured image and an accompanying video were taken late in 2019 over Ostersund, Sweden.

APOD: 2024 July 6 - NGC 7789: Caroline s Rose
Explanation: Found among the rich starfields of the Milky Way, star cluster NGC 7789 lies about 8,000 light-years away toward the constellation Cassiopeia. A late 18th century deep sky discovery of astronomer Caroline Lucretia Herschel, the cluster is also known as Caroline's Rose. Its visual appearance in small telescopes, created by the cluster's complex of stars and voids, is suggestive of nested rose petals. Now estimated to be 1.6 billion years young, the galactic or open cluster of stars also shows its age. All the stars in the cluster were likely born at the same time, but the brighter and more massive ones have more rapidly exhausted the hydrogen fuel in their cores. These have evolved from main sequence stars like the Sun into the many red giant stars shown with a yellowish cast in this color composite. Using measured color and brightness, astronomers can model the mass and hence the age of the cluster stars just starting to "turn off" the main sequence and become red giants. Over 50 light-years across, Caroline's Rose spans about half a degree (the angular size of the Moon) near the center of the sharp telescopic image.

APOD: 2024 July 5 - Mount Etna Milky Way
Explanation: A glow from the summit of Mount Etna, famous active stratovolcano of planet Earth, stands out along the horizon in this mountain and night skyscape. Bands of diffuse light from congeries of innumerable stars along the Milky Way galaxy stretch across the sky above. In silhouette, the Milky Way's massive dust clouds are clumped along the galactic plane. Also familiar to northern skygazers are bright stars Deneb, Vega, and Altair, the Summer Triangle straddling dark nebulae and luminous star clouds poised over the volcanic peak. The deep combined exposures reveal the light of active star forming regions along the Milky Way, echoing Etna's ruddy hue in the northern hemisphere summer's night.

APOD: 2024 July 4 - A Beautiful Trifid
Explanation: The beautiful Trifid Nebula is a cosmic study in contrasts. Also known as M20, it lies about 5,000 light-years away toward the nebula rich constellation Sagittarius. A star forming region in the plane of our galaxy, the Trifid does illustrate three different types of astronomical nebulae; red emission nebulae dominated by light from hydrogen atoms, blue reflection nebulae produced by dust reflecting starlight, and dark nebulae where dense dust clouds appear in silhouette. But the red emission region, roughly separated into three parts by obscuring dust lanes, is what lends the Trifid its popular name. Pillars and jets sculpted by newborn stars, above and right of the emission nebula's center, appear in famous Hubble Space Telescope close-up images of the region. The Trifid Nebula is about 40 light-years across. Too faint to be seen by the unaided eye, it almost covers the area of a full moon on planet Earth's sky.

APOD: 2024 June 30 – Earthrise: A Video Reconstruction
Explanation: About 12 seconds into this video, something unusual happens. The Earth begins to rise. Never seen by humans before, the rise of the Earth over the limb of the Moon occurred about 55.5 years ago and surprised and amazed the crew of Apollo 8. The crew immediately scrambled to take still images of the stunning vista caused by Apollo 8's orbit around the Moon. The featured video is a modern reconstruction of the event as it would have looked were it recorded with a modern movie camera. The colorful orb of our Earth stood out as a familiar icon rising above a distant and unfamiliar moonscape, the whole scene the conceptual reverse of a more familiar moonrise as seen from Earth. To many, the scene also spoke about the unity of humanity: that big blue marble -- that's us -- we all live there. The two-minute video is not time-lapse -- this is the real speed of the Earth rising through the windows of Apollo 8. Seven months and three missions later, Apollo 11 astronauts would not only circle Earth's moon, but land on it.

APOD: 2024 June 29 - A Solstice Moon
Explanation: Rising opposite the setting Sun, June's Full Moon occurred within about 28 hours of the solstice. The Moon stays close to the Sun's path along the ecliptic plane and so while the solstice Sun climbed high in daytime skies, June's Full Moon remained low that night as seen from northern latitudes. In fact, the Full Moon hugs the horizon in this June 21 rooftop night sky view from Bursa, Turkey, constructed from exposures made every 10 minutes between moonrise and moonset. In 2024 the Moon also reached a major lunar standstill, an extreme in the monthly north-south range of moonrise and moonset caused by the precession of the Moon's orbit over an 18.6 year cycle. As a result, this June solstice Full Moon was at its southernmost moonrise and moonset along the horizon.

APOD: 2024 June 28 - Comet 13P/Olbers
Explanation: Not a paradox, Comet 13P/Olbers is returning to the inner Solar System after 68 years. The periodic, Halley-type comet will reach its next perihelion or closest approach to the Sun on June 30 and has become a target for binocular viewing low in planet Earth's northern hemisphere night skies. But this sharp telescopic image of 13P is composed of stacked exposures made on the night of June 25. It easily reveals shifting details in the bright comet's torn and tattered ion tail buffeted by the wind from an active Sun, along with a broad, fanned-out dust tail and slightly greenish coma. The frame spans over two degrees across a background of faint stars toward the constellation Lynx.

APOD: 2024 June 27 - Protostellar Outflows in Serpens
Explanation: Jets of material blasting from newborn stars, are captured in this James Webb Space Telescope close-up of the Serpens Nebula. The powerful protostellar outflows are bipolar, twin jets spewing in opposite directions. Their directions are perpendicular to accretion disks formed around the spinning, collapsing stellar infants. In the NIRcam image, the reddish color represents emission from molecular hydrogen and carbon monoxide produced as the jets collide with the surrounding gas and dust. The sharp image shows for the first time that individual outflows detected in the Serpens Nebula are generally aligned along the same direction. That result was expected, but has only now come into clear view with Webb's detailed exploration of the active young star-forming region. Brighter foreground stars exhibit Webb's characteristic diffraction spikes. At the Serpens Nebula's estimated distance of 1,300 light-years, this cosmic close-up frame is about 1 light-year across.

APOD: 2024 June 26 – Timelapse: Aurora, SAR, and the Milky Way
Explanation: What's happening in the sky this unusual night? Most striking in the featured 4.5-hour 360-degree panoramic video, perhaps, is the pink and purple aurora. That's because this night, encompassing May 11, was famous for its auroral skies around the world. As the night progresses, auroral bands shimmer, the central band of our Milky Way Galaxy rises, and stars shift as the Earth rotates beneath them. Captured here simultaneously is a rare red band running above the aurora: a SAR arc, seen to change only slightly. The flashing below the horizon is caused by passing cars, while the moving spots in the sky are satellites and airplanes. The featured video was captured from Xinjiang, China with four separate cameras.

APOD: 2024 June 25 – The Dark Doodad Nebula
Explanation: What is that strange brown ribbon on the sky? When observing the star cluster NGC 4372, observers frequently take note of an unusual dark streak nearby running about three degrees in length. The streak, actually a long molecular cloud, has become known as the Dark Doodad Nebula. (Doodad is slang for a thingy or a whatchamacallit.) Pictured here, the Dark Doodad Nebula sweeps across the center of a rich and colorful starfield. Its dark color comes from a high concentration of interstellar dust that preferentially scatters visible light. The globular star cluster NGC 4372 is visible as the fuzzy white spot on the far left, while the bright blue star gamma Muscae is seen to the cluster's upper right. The Dark Doodad Nebula can be found with strong binoculars toward the southern constellation of the Fly (Musca).

APOD: 2024 June 20 - Sandy and the Moon Halo
Explanation: Last April's Full Moon shines through high clouds near the horizon, casting shadows in this garden-at-night skyscape. Along with canine sentinel Sandy watching the garden gate, the wide-angle snapshot also captured the bright Moon's 22 degree ice halo. But June's bright Full Moon will cast shadows too. This month, the Moon's exact full phase occurs at 01:08 UTC June 22. That's a mere 28 hours or so after today's June solstice (at 20:51 UTC June 20), the moment when the Sun reaches its maximum northern declination. Known to some as a Strawberry Moon, June's Full Moon is at its southernmost declination, and of course will create its own 22 degree halos in hazy night skies.

APOD: 2024 June 17 – Ou4: The Giant Squid Nebula
Explanation: Squids on Earth aren't this big. This mysterious squid-like cosmic cloud spans nearly three full moons on planet Earth's sky. Discovered in 2011 by French astro-imager Nicolas Outters, the Squid Nebula's bipolar shape is distinguished here by the telltale blue emission from doubly ionized oxygen atoms. Though apparently surrounded by the reddish hydrogen emission region Sh2-129, the true distance and nature of the Squid Nebula have been difficult to determine. Still, one investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, the cosmic squid would represent a spectacular outflow of material driven by a triple system of hot, massive stars, cataloged as HR8119, seen near the center of the nebula. If so, this truly giant squid nebula would physically be over 50 light-years across.

APOD: 2024 June 14 - RCW 85
Explanation: From the 1960 astronomical catalog of Rodgers, Campbell and Whiteoak, emission region RCW 85 shines in southern night skies between bright stars Alpha and Beta Centauri. About 5,000 light years distant, the hazy interstellar cloud of glowing hydrogen gas and dust is faint. But detailed structures along well-defined rims within RCW 85 are traced in this cosmic skyscape composed of 28 hours of narrow and broadband exposures. Suggestive of dramatic shapes in other stellar nurseries where natal clouds of gas and dust are sculpted by energetic winds and radiation from newborn stars, the tantalizing nebula has been called the Devil's Tower. This telescopic frame would span around 100 light-years at the estimated distance of RCW 85.

APOD: 2024 June 13 - Messier 66 Close Up
Explanation: Big, beautiful spiral galaxy Messier 66 lies a mere 35 million light-years away. The gorgeous island universe is about 100 thousand light-years across, similar in size to the Milky Way. This Hubble Space Telescope close-up view spans a region about 30,000 light-years wide around the galactic core. It shows the galaxy's disk dramatically inclined to our line-of-sight. Surrounding its bright core, the likely home of a supermassive black hole, obscuring dust lanes and young, blue star clusters sweep along spiral arms dotted with the tell-tale glow of pinkish star forming regions. Messier 66, also known as NGC 3627, is the brightest of the three galaxies in the gravitationally interacting Leo Triplet.

APOD: 2024 June 12 – Aurora over Karkonosze Mountains
Explanation: It was the first time ever. At least, the first time this photographer had ever seen aurora from his home mountains. And what a spectacular aurora it was. The Karkonosze Mountains in Poland are usually too far south to see any auroras. But on the amazing night of May 10 - 11, purple and green colors lit up much of the night sky, a surprising spectacle that also appeared over many mid-latitude locations around the Earth. The featured image is a composite of six vertical exposures taken during the auroral peak. The futuristic buildings on the right are part of a meteorological observatory located on the highest peak of the Karkonosze Mountains. The purple color is primarily due to Sun-triggered, high-energy electrons impacting nitrogen molecules in Earth's atmosphere. Our Sun is reaching its maximum surface activity over the next two years, and although many more auroras are predicted, most will occur over regions closer to the Earth's poles.

APOD: 2024 June 11 – Colorful Stars and Clouds near Rho Ophiuchi
Explanation: Why is the sky near Antares and Rho Ophiuchi so colorful, yet dusty? The colors result from a mixture of objects and processes. Fine dust -- illuminated by starlight -- produces blue reflection nebulae. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae. Backlit dust clouds block starlight and so appear dark. Antares, a red supergiant and one of the brighter stars in the night sky, lights up the yellow-red clouds on the upper right of the featured image. The Rho Ophiuchi star system lies at the center of the blue reflection nebula on the left, while a different reflection nebula, IC 4605, lies just below and right of the image center. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum.

APOD: 2024 June 9 – How to Identify that Light in the Sky
Explanation: What is that light in the sky? The answer to one of humanity's more common questions may emerge from a few quick observations. For example -- is it moving or blinking? If so, and if you live near a city, the answer is typically an airplane, since planes are so numerous and so few stars and satellites are bright enough to be seen over the glare of artificial city lights. If not, and if you live far from a city, that bright light is likely a planet such as Venus or Mars -- the former of which is constrained to appear near the horizon just before dawn or after dusk. Sometimes the low apparent motion of a distant airplane near the horizon makes it hard to tell from a bright planet, but even this can usually be discerned by the plane's motion over a few minutes. Still unsure? The featured chart gives a sometimes-humorous but mostly-accurate assessment. Dedicated sky enthusiasts will likely note -- and are encouraged to provide -- polite corrections.

APOD: 2024 June 8 - Pandora's Cluster of Galaxies
Explanation: This deep field mosaicked image presents a stunning view of galaxy cluster Abell 2744 recorded by the James Webb Space Telescope's NIRCam. Also dubbed Pandora's Cluster, Abell 2744 itself appears to be a ponderous merger of three different massive galaxy clusters. It lies some 3.5 billion light-years away, toward the constellation Sculptor. Dominated by dark matter, the mega-cluster warps and distorts the fabric of spacetime, gravitationally lensing even more distant objects. Redder than the Pandora cluster galaxies many of the lensed sources are very distant galaxies in the early Universe, their lensed images stretched and distorted into arcs. Of course distinctive diffraction spikes mark foreground Milky Way stars. At the Pandora Cluster's estimated distance this cosmic box spans about 6 million light-years. But don't panic. You can explore the tantalizing region in a 2 minute video tour.

APOD: 2024 June 7 - Sharpless 308: The Dolphin Head Nebula
Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as Sharpless 2-308 it lies some 5,000 light-years away toward the well-trained constellation Canis Major and covers slightly more of the sky than a Full Moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured by narrowband filters in the deep image is dominated by the glow of ionized oxygen atoms mapped to a blue hue. Presenting a mostly harmless outline, SH2-308 is also known as The Dolphin-head Nebula.

APOD: 2024 June 5 – Shadow of a Martian Robot
Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might be the Perseverance rover exploring Mars. Perseverance has been examining the Red Planet since 2021, finding evidence of its complex history of volcanism and ancient flowing water, and sending breathtaking images across the inner Solar System. Pictured here in February of 2024, Perseverance looks opposite the Sun and across Neretva Vallis in Jezero Crater, with a local hill visible at the top of the frame. The distinctively non-human shadow of the car-sized rover is visible below center, superposed on scattered rocks. Perseverance, now working without its flying companion Ingenuity, continues to search Mars for signs of ancient life.

APOD: 2024 June 4 – Comet Pons Brooks Develops Opposing Tails
Explanation: Why does Comet Pons-Brooks now have tails pointing in opposite directions? The most spectacular tail is the blue-glowing ion tail that is visible flowing down the image. The ion tail is pushed directly out from the Sun by the solar wind. On the upper right is the glowing central coma of Comet 12P/Pons–Brooks. Fanning out from the coma, mostly to the left, is the comet's dust tail. Pushed out and slowed down by the pressure of sunlight, the dust tail tends to trail the comet along its orbit and, from some viewing angles, can appear opposite to the ion tail. The distant, bright star Alpha Leporis is seen at the bottom of the featured image captured last week from Namibia. Two days ago, the comet passed its closest to the Earth and is now best visible from southern skies as it dims and glides back to the outer Solar System.

APOD: 2024 June 2 – Rotating Moon from LRO
Explanation: No one, presently, sees the Moon rotate like this. That's because the Earth's moon is tidally locked to the Earth, showing us only one side. Given modern digital technology, however, combined with many detailed images returned by the Lunar Reconnaissance Orbiter (LRO), a high resolution virtual Moon rotation movie has been composed. The featured time-lapse video starts with the standard Earth view of the Moon. Quickly, though, Mare Orientale, a large crater with a dark center that is difficult to see from the Earth, rotates into view just below the equator. From an entire lunar month condensed into 24 seconds, the video clearly shows that the Earth side of the Moon contains an abundance of dark lunar maria, while the lunar far side is dominated by bright lunar highlands. Currently, over 32 new missions to the Moon are under active development from multiple countries and companies, including NASA's Artemis program which aims to land people on the Moon again within the next few years.

APOD: 2024 May 29 – Stairway to the Milky Way
Explanation: What happens if you ascend this stairway to the Milky Way? Before answering that, let's understand the beautiful sky you will see. Most eye-catching is the grand arch of the Milky Way Galaxy, the band that is the central disk of our galaxy which is straight but distorted by the wide-angle nature of this composite image. Many stars well in front of the Milk Way will be visible, with the bright white star just below the stellar arch being Altair, and the bright blue star above it being Vega. The air glows green on the left, just above the yellow cloud deck. The featured image was taken last month on Portugal's Madeira Island in the North Atlantic Ocean. Oh, and what happens after you reach the top of these stairs and admire the amazing sky is, quite probably, that you then descend down the stairs on the other side.

APOD: 2024 May 28 – Solar X Flare as Famous Active Region Returns
Explanation: It's back. The famous active region on the Sun that created auroras visible around the Earth earlier this month has survived its rotation around the far side of the Sun -- and returned. Yesterday, as it was beginning to reappear on the Earth-facing side, the region formerly labeled AR 3664 threw another major solar flare, again in the highest-energy X-class range. The featured video shows the emerging active region on the lower left, as it was captured by NASA's Earth-orbiting Solar Dynamics Observatory yesterday in ultraviolet light. The video is a time-lapse of the entire Sun rotating over 24 hours. Watch the lower-left region carefully at about the 2-second mark to see the powerful flare burst out. The energetic particles from that flare and associated CME are not expected to directly impact the Earth and trigger impressive auroras, but scientists will keep a close watch on this unusually active region over the next two weeks, as it faces the Earth, to see what develops.

APOD: 2024 May 25 - Manicouagan Impact Crater from Space
Explanation: Orbiting 400 kilometers above Quebec, Canada, planet Earth, the International Space Station Expedition 59 crew captured this snapshot of the broad St. Lawrence River and curiously circular Lake Manicouagan on April 11. Right of center, the ring-shaped lake is a modern reservoir within the eroded remnant of an ancient 100 kilometer diameter impact crater. The ancient crater is very conspicuous from orbit, a visible reminder that Earth is vulnerable to rocks from space. Over 200 million years old, the Manicouagan crater was likely caused by the impact of a rocky body about 5 kilometers in diameter. Currently, there is no known asteroid with a significant probability of impacting Earth in the next century. Each month, NASA’s Planetary Defense Coordination Office releases an update featuring the most recent figures on near-Earth object close approaches, and other facts about comets and asteroids that could pose a potential impact hazard with Earth.

APOD: 2024 May 24 – M78 from the Euclid Space Telescope
Explanation: Star formation can be messy. To help find out just how messy, ESA's new Sun-orbiting Euclid telescope recently captured the most detailed image ever of the bright star forming region M78. Near the image center, M78 lies at a distance of only about 1,300 light-years away and has a main glowing core that spans about 5 light-years. The featured image was taken in both visible and infrared light. The purple tint in M78's center is caused by dark dust preferentially reflecting the blue light of hot, young stars. Complex dust lanes and filaments can be traced through this gorgeous and revealing skyscape. On the upper left is associated star forming region NGC 2071, while a third region of star formation is visible on the lower right. These nebulas are all part of the vast Orion Molecular Cloud Complex which can be found with even a small telescope just north of Orion's belt.

APOD: 2024 May 23 - Unraveling NGC 3169
Explanation: Spiral galaxy NGC 3169 looks to be unraveling like a ball of cosmic yarn. It lies some 70 million light-years away, south of bright star Regulus toward the faint constellation Sextans. Wound up spiral arms are pulled out into sweeping tidal tails as NGC 3169 (left) and neighboring NGC 3166 interact gravitationally. Eventually the galaxies will merge into one, a common fate even for bright galaxies in the local universe. Drawn out stellar arcs and plumes are clear indications of the ongoing gravitational interactions across the deep and colorful galaxy group photo. The telescopic frame spans about 20 arc minutes or about 400,000 light-years at the group's estimated distance, and includes smaller, bluish NGC 3165 to the right. NGC 3169 is also known to shine across the spectrum from radio to X-rays, harboring an active galactic nucleus that is the site of a supermassive black hole.

APOD: 2024 May 21 – CG4: The Globule and the Galaxy
Explanation: Can a gas cloud eat a galaxy? It's not even close. The "claw" of this odd looking "creature" in the featured photo is a gas cloud known as a cometary globule. This globule, however, has ruptured. Cometary globules are typically characterized by dusty heads and elongated tails. These features cause cometary globules to have visual similarities to comets, but in reality they are very much different. Globules are frequently the birthplaces of stars, and many show very young stars in their heads. The reason for the rupture in the head of this object is not yet known. The galaxy to the left of the globule is huge, very far in the distance, and only placed near CG4 by chance superposition.

APOD: 2024 May 20 – Aurora Dome Sky
Explanation: It seemed like night, but part of the sky glowed purple. It was the now famous night of May 10, 2024, when people over much of the world reported beautiful aurora-filled skies. The featured image was captured this night during early morning hours from Arlington, Wisconsin, USA. The panorama is a composite of several 6-second exposures covering two thirds of the visible sky, with north in the center, and processed to heighten the colors and remove electrical wires. The photographer (in the foreground) reported that the aurora appeared to flow from a point overhead but illuminated the sky only toward the north. The aurora's energetic particles originated from CMEs ejected from our Sun over sunspot AR 3664 a few days before. This large active region rotated to the far side of the Sun last week, but may well survive to rotate back toward the Earth next week.

APOD: 2024 May 18 - North Celestial Aurora
Explanation: Graceful star trail arcs reflect planet Earth's daily rotation in this colorful night skyscape. To create the timelapse composite, on May 12 consecutive exposures were recorded with a camera fixed to a tripod on the shores of the Ashokan Reservoir, in the Catskills region of New York, USA. North star Polaris is near the center of the star trail arcs. The broad trail of a waxing crescent Moon is on the left, casting a strong reflection across the reservoir waters. With intense solar activity driving recent geomagnetic storms, the colorful aurora borealis or northern lights, rare to the region, shine under Polaris and the north celestial pole.

APOD: 2024 May 17 - Aurora Banks Peninsula
Explanation: This well-composed composite panoramic view looks due south from Banks Peninsula near Christchurch on New Zealand's South Island. The base of a tower-like rocky sea stack is awash in the foreground, with stars of the Southern Cross at the top of the frame and planet Earth's south celestial pole near center. Still, captured on May 11, vibrant aurora australis dominate the starry southern sea and skyscape. The shimmering southern lights were part of extensive auroral displays that entertained skywatchers in northern and southern hemispheres around planet Earth, caused by intense geomagnetic storms. The extreme spaceweather was triggered by the impact of coronal mass ejections launched from powerful solar active region AR 3664.

APOD: 2024 May 16 - Aurora Georgia
Explanation: A familiar sight from Georgia, USA, the Moon sets near the western horizon in this rural night skyscape. Captured on May 10 before local midnight, the image overexposes the Moon's bright waxing crescent at left in the frame. A long irrigation rig stretches across farmland about 15 miles north of the city of Bainbridge. Shimmering curtains of aurora shine across the starry sky, definitely an unfamiliar sight for southern Georgia nights. Last weekend, extreme geomagnetic storms triggered by the recent intense activity from solar active region AR 3664 brought epic displays of aurora, usually seen closer to the poles, to southern Georgia and even lower latitudes on planet Earth. As solar activity ramps up, more storms are possible.

APOD: 2024 May 14 - The 37 Cluster
Explanation: For the mostly harmless denizens of planet Earth, the brighter stars of open cluster NGC 2169 seem to form a cosmic 37. Did you expect 42? From our perspective, the improbable numerical asterism appears solely by chance. It lies at an estimated distance of 3,300 light-years toward the constellation Orion. As far as galactic or open star clusters go, NGC 2169 is a small one, spanning about 7 light-years. Formed at the same time from the same cloud of dust and gas, the stars of NGC 2169 are only about 11 million years old. Such clusters are expected to disperse over time as they encounter other stars, interstellar clouds, and experience gravitational tides while hitchhiking through the galaxy. Over four billion years ago, our own Sun was likely formed in a similar open cluster of stars.

APOD: 2024 May 13 – AR 3664 on a Setting Sun
Explanation: It was larger than the Earth. It was so big you could actually see it on the Sun's surface without magnification. It contained powerful and tangled magnetic fields as well as numerous dark sunspots. Labelled AR 3664, it developed into one of the most energetic areas seen on the Sun in recent years, unleashing a series of explosions that led to a surge of energetic particles striking the Earth, which created beautiful auroras. And might continue. Although active regions on the Sun like AR 3664 can be quite dangerous, this region's Coronal Mass Ejections have not done, as yet, much damage to Earth-orbiting satellites or Earth-surface electrical grids. Pictured, the enormous active region was captured on the setting Sun a few days ago from Civitavecchia, Rome, Italy. The composite image includes a very short exposure taken of just the Sun's surface, but mimics what was actually visible. Finally, AR 3664 is now rotating away from the Earth, although the region may survive long enough to come around again.

APOD: 2024 May 12 – Red Aurora over Poland
Explanation: Northern lights don't usually reach this far south. Magnetic chaos in the Sun's huge Active Region 3664, however, produced a surface explosion that sent a burst of electrons, protons, and more massive, charged nuclei into the Solar System. A few days later, that coronal mass ejection (CME) impacted the Earth and triggered auroras that are being reported unusually far from our planet's north and south poles. The free sky show might not be over -- the sunspot rich AR3664 has ejected even more CMEs that might also impact the Earth tonight or tomorrow. That active region is now near the Sun's edge, though, and will soon be rotating away from the Earth. Pictured, a red and rayed aurora was captured in a single 6-second exposure from Racibórz, Poland early last night. The photographer's friend, seeing an aurora for the first time, is visible in the distance also taking images of the beautifully colorful nighttime sky.

APOD: 2024 May 11 – AR 3664: Giant Sunspot Group
Explanation: Right now, one of the largest sunspot groups in recent history is crossing the Sun. Active Region 3664 is not only big -- it's violent, throwing off clouds of particles into the Solar System. Some of these CMEs are already impacting the Earth, and others might follow. At the extreme, these solar storms could cause some Earth-orbiting satellites to malfunction, the Earth's atmosphere to slightly distort, and electrical power grids to surge. When impacting Earth's upper atmosphere, these particles can produce beautiful auroras, with some auroras already being reported unusually far south. Pictured here, AR3664 and its dark sunspots were captured yesterday in visible light from Rome, Italy. The AR3664 sunspot group is so large that it is visible just with glasses designed to view last month's total solar eclipse. This weekend, skygazing enthusiasts will be keenly watching the night skies all over the globe for bright and unusual auroras.

APOD: 2024 May 10 - Simulation: Two Black Holes Merge
Explanation: Relax and watch two black holes merge. Inspired by the first direct detection of gravitational waves in 2015, this simulation plays in slow motion but would take about one third of a second if run in real time. Set on a cosmic stage, the black holes are posed in front of stars, gas, and dust. Their extreme gravity lenses the light from behind them into Einstein rings as they spiral closer and finally merge into one. The otherwise invisible gravitational waves generated as the massive objects rapidly coalesce cause the visible image to ripple and slosh both inside and outside the Einstein rings even after the black holes have merged. Dubbed GW150914, the gravitational waves detected by LIGO are consistent with the merger of 36 and 31 solar mass black holes at a distance of 1.3 billion light-years. The final, single black hole has 63 times the mass of the Sun, with the remaining 3 solar masses converted into energy radiated in gravitational waves.

APOD: 2024 May 9 - The Galaxy, the Jet, and a Famous Black Hole
Explanation: Bright elliptical galaxy Messier 87 (M87) is home to the supermassive black hole captured in 2017 by planet Earth's Event Horizon Telescope in the first ever image of a black hole. Giant of the Virgo galaxy cluster about 55 million light-years away, M87 is rendered in blue hues in this infrared image from the Spitzer Space telescope. Though M87 appears mostly featureless and cloud-like, the Spitzer image does record details of relativistic jets blasting from the galaxy's central region. Shown in the inset at top right, the jets themselves span thousands of light-years. The brighter jet seen on the right is approaching and close to our line of sight. Opposite, the shock created by the otherwise unseen receding jet lights up a fainter arc of material. Inset at bottom right, the historic black hole image is shown in context at the center of giant galaxy, between the relativistic jets. Completely unresolved in the Spitzer image, the supermassive black hole surrounded by infalling material is the source of enormous energy driving the relativistic jets from the center of active galaxy M87. The Event Horizon Telescope image of M87 has been enhanced to reveal a sharper view of the famous supermassive black hole.

APOD: 2024 May 7 – Black Hole Accreting with Jet
Explanation: What happens when a black hole devours a star? Many details remain unknown, but observations are providing new clues. In 2014, a powerful explosion was recorded by the ground-based robotic telescopes of the All Sky Automated Survey for SuperNovae (Project ASAS-SN), with followed-up observations by instruments including NASA's Earth-orbiting Swift satellite. Computer modeling of these emissions fit a star being ripped apart by a distant supermassive black hole. The results of such a collision are portrayed in the featured artistic illustration. The black hole itself is a depicted as a tiny black dot in the center. As matter falls toward the hole, it collides with other matter and heats up. Surrounding the black hole is an accretion disk of hot matter that used to be the star, with a jet emanating from the black hole's spin axis.

APOD: 2024 May 6 – A Total Solar Eclipse from Sliver to Ring
Explanation: This is how the Sun disappeared from the daytime sky last month. The featured time-lapse video was created from stills taken from Mountain View, Arkansas, USA on 2024 April 8. First, a small sliver of a normally spotted Sun went strangely dark. Within a few minutes, much of the background Sun was hidden behind the advancing foreground Moon. Within an hour, the only rays from the Sun passing the Moon appeared like a diamond ring. During totality, most of the surrounding sky went dark, making the bright pink prominences around the Sun's edge stand out, and making the amazing corona appear to spread into the surrounding sky. The central view of the corona shows an accumulation of frames taken during complete totality. As the video ends, just a few minutes later, another diamond ring appeared -- this time on the other side of the Moon. Within the next hour, the sky returned to normal.

APOD: 2024 May 5 – A Black Hole Disrupts a Passing Star
Explanation: What happens to a star that goes near a black hole? If the star directly impacts a massive black hole, then the star falls in completely -- and everything vanishes. More likely, though, the star goes close enough to have the black hole's gravity pull away its outer layers, or disrupt, the star. Then, most of the star's gas does not fall into the black hole. These stellar tidal disruption events can be as bright as a supernova, and an increasing amount of them are being discovered by automated sky surveys. In the featured artist's illustration, a star has just passed a massive black hole and sheds gas that continues to orbit. The inner edge of a disk of gas and dust surrounding the black hole is heated by the disruption event and may glow long after the star is gone.

APOD: 2024 May 4 - 3 ATs
Explanation: Despite their resemblance to R2D2, these three are not the droids you're looking for. Instead, the enclosures house 1.8 meter Auxiliary Telescopes (ATs) at Paranal Observatory in the Atacama Desert region of Chile. The ATs are designed to be used for interferometry, a technique for achieving extremely high resolution observations, in concert with the observatory's 8 meter Very Large Telescope units. A total of four ATs are operational, each fitted with a transporter that moves the telescope along a track allowing different arrays with the large unit telescopes. To work as an interferometer, the light from each telescope is brought to a common focal point by a system of mirrors in underground tunnels. Above these three ATs, the Large and Small Magellanic Clouds are the far, far away satellite galaxies of our own Milky Way. In the clear and otherwise dark southern skies, planet Earth's greenish atmospheric airglow stretches faintly along the horizon.

APOD: 2024 May 3 - Temperatures on Exoplanet WASP 43b
Explanation: A mere 280 light-years from Earth, tidally locked, Jupiter-sized exoplanet WASP-43b orbits its parent star once every 0.8 Earth days. That puts it about 2 million kilometers (less than 1/25th the orbital distance of Mercury) from a small, cool sun. Still, on a dayside always facing its parent star, temperatures approach a torrid 2,500 degrees F as measured at infrared wavelengths by the MIRI instrument on board the James Webb Space Telescope. In this illustration of the hot exoplanet's orbit, Webb measurements also show nightside temperatures remain above 1,000 degrees F. That suggests that strong equatorial winds circulate the dayside atmospheric gases to the nightside before they can completely cool off. Exoplanet WASP-43b is now formally known as Astrolábos, and its K-type parent star has been christened Gnomon. Webb's infrared spectra indicate water vapor is present on the nightside as well as the dayside of the planet, providing information about cloud cover on Astrolábos.

APOD: 2024 May 2 - M100: A Grand Design Spiral Galaxy
Explanation: Majestic on a truly cosmic scale, M100 is appropriately known as a grand design spiral galaxy. The large galaxy of over 100 billion stars has well-defined spiral arms, similar to our own Milky Way. One of the brightest members of the Virgo Cluster of galaxies, M100, also known as NGC 4321 is 56 million light-years distant toward the well-groomed constellation Coma Berenices. In this telescopic image, the face-on grand design spiral shares a nearly 1 degree wide field-of-view with slightly less conspicuous edge-on spiral NGC 4312 (at upper right). The 21 hour long equivalent exposure from a dark sky site near Flagstaff, Arizona, planet Earth, reveals M100's bright blue star clusters and intricate winding dust lanes which are hallmarks of this class of galaxies. Measurements of variable stars in M100 have played an important role in determining the size and age of the Universe.

APOD: 2024 April 29 – Comet, Planet, Moon
Explanation: Three bright objects satisfied seasoned stargazers of the western sky just after sunset earlier this month. The most familiar was the Moon, seen on the upper left in a crescent phase. The rest of the Moon was faintly visible by sunlight first reflected by the Earth. The bright planet Jupiter, the largest planet in the Solar System, is seen to the upper left. Most unusual was Comet 12P/Pons-Brooks, below the Moon and showing a stubby dust tail on the right but an impressive ion tail extending upwards. The featured image, a composite of several images taken consecutively at the same location and with the same camera, was taken near the village of Llers, in Spain's Girona province. Comet Pons-Brooks passed its closest to the Sun last week and is now dimming as it moves into southern skies and returns to the outer Solar System.

APOD: 2024 April 26 - Regulus and the Dwarf Galaxy
Explanation: In northern hemisphere spring, bright star Regulus is easy to spot above the eastern horizon. The alpha star of the constellation Leo, Regulus is the spiky star centered in this telescopic field of view. A mere 79 light-years distant, Regulus is a hot, rapidly spinning star that is known to be part of a multiple star system. Not quite lost in the glare, the fuzzy patch just below Regulus is diffuse starlight from small galaxy Leo I. Leo I is a dwarf spheroidal galaxy, a member of the Local Group of galaxies dominated by our Milky Way Galaxy and the Andromeda Galaxy (M31). About 800 thousand light-years away, Leo I is thought to be the most distant of the known small satellite galaxies orbiting the Milky Way. But dwarf galaxy Leo I has shown evidence of a supermassive black hole at its center, comparable in mass to the black hole at the center of the Milky Way.

APOD: 2024 April 24 – Dragons Egg Bipolar Emission Nebula
Explanation: How did a star form this beautiful nebula? In the middle of emission nebula NGC 6164 is an unusually massive star. The central star has been compared to an oyster's pearl and an egg protected by the mythical sky dragons of Ara. The star, visible in the center of the featured image and catalogued as HD 148937, is so hot that the ultraviolet light it emits heats up gas that surrounds it. That gas was likely thrown off from the star previously, possibly the result of a gravitational interaction with a looping stellar companion. Expelled material might have been channeled by the magnetic field of the massive star, in all creating the symmetric shape of the bipolar nebula. NGC 6164 spans about four light years and is located about 3,600 light years away toward the southern constellation Norma.

APOD: 2024 April 23 – Contrail Shadow X
Explanation: What created this giant X in the clouds? It was the shadow of contrails. When airplanes fly, humid engine exhaust may form water droplets that might freeze in Earth's cold upper atmosphere. These persistent streams of water and ice scatter light from the Sun above and so appear bright. These contrails cast long shadows. That was just the case over Istanbul, Türkiye, earlier this month. Contrails occur all over planet Earth and, generally, warm the Earth when the trap infrared light but cool the Earth when they efficiently reflect sunlight. The image was taken by a surprised photographer in the morning on the way to work.

APOD: 2024 April 22 – Moon and Smoke Rings from Mt Etna
Explanation: Yes, but can your volcano do this? To the surprise of some, Mt. Etna emits, on occasion, smoke rings. Technically known as vortex rings, the walls of the volcano slightly slow the outside of emitted smoke puffs, causing the inside gas to move faster. A circle of low pressure develops so that the emitted puff of volcanic gas and ash loops around in a ring, a familiar geometric structure that can be surprisingly stable as it rises. Smoke rings are quite rare and need a coincidence of the right geometry of the vent, the right speed of ejected smoke, and the relative calmness of the outside atmosphere. In the featured image taken about two weeks ago from Gangi, Sicily, Italy, multiple volcanic smoke rings are visible. The scene is shaded by the red light of a dawn Sun, while a crescent Moon is visible in the background.

APOD: 2024 April 18 - Facing NGC 1232
Explanation: From our vantage point in the Milky Way Galaxy, we see NGC 1232 face-on. Nearly 200,000 light-years across, the big, beautiful spiral galaxy is located some 47 million light-years away in the flowing southern constellation of Eridanus. This sharp, multi-color, telescopic image of NGC 1232 includes remarkable details of the distant island universe. From the core outward, the galaxy's colors change from the yellowish light of old stars in the center to young blue star clusters and reddish star forming regions along the grand, sweeping spiral arms. NGC 1232's apparent, small, barred-spiral companion galaxy is cataloged as NGC 1232A. Distance estimates place it much farther though, around 300 million light-years away, and unlikely to be interacting with NGC 1232. Of course, the prominent bright star with the spiky appearance is much closer than NGC 1232 and lies well within our own Milky Way.

APOD: 2024 April 17 – Total Eclipse and Comets
Explanation: Not one, but two comets appeared near the Sun during last week's total solar eclipse. The expected comet was Comet 12P/Pons-Brooks, but it was disappointingly dimmer than many had hoped. However, relatively unknown Comet SOHO-5008 also appeared in long duration camera exposures. This comet was the 5008th comet identified on images taken by ESA & NASA's Sun-orbiting SOHO spacecraft. Likely much smaller, Comet SOHO-5008 was a sungrazer which disintegrated within hours as it passed too near the Sun. The featured image is not only unusual for capturing two comets during an eclipse, but one of the rare times that a sungrazing comet has been photographed from the Earth's surface. Also visible in the image is the sprawling corona of our Sun and the planets Mercury (left) and Venus (right). Of these planets and comets, only Venus was easily visible to millions of people in the dark shadow of the Moon that crossed North America on April 8.

APOD: 2024 April 16 – Filaments of the Vela Supernova Remnant
Explanation: The explosion is over, but the consequences continue. About eleven thousand years ago, a star in the constellation of Vela could be seen to explode, creating a strange point of light briefly visible to humans living near the beginning of recorded history. The outer layers of the star crashed into the interstellar medium, driving a shock wave that is still visible today. The featured image captures some of that filamentary and gigantic shock in visible light. As gas flies away from the detonated star, it decays and reacts with the interstellar medium, producing light in many different colors and energy bands. Remaining at the center of the Vela Supernova Remnant is a pulsar, a star as dense as nuclear matter that spins around more than ten times in a single second.

APOD: 2024 April 14 – How a Total Solar Eclipse Ended
Explanation: How does a total solar eclipse end? Yes, the Moon moves out from fully blocking the Sun, but in the first few seconds of transition, interesting things appear. The first is called a diamond ring. Light might stream between mountains or through relative lowlands around the Moon's edge, as seen from your location, making this sudden first light, when combined with the corona that surrounds the Moon, look like a diamond ring. Within seconds other light streams appear that are called, collectively, Bailey's beads. In the featured video, it may seem that the pink triangular prominence on the Sun is somehow related to where the Sun begins to reappear, but it is not. Observers from other locations saw Bailey's beads emerge from different places around the Moon, away from the iconic triangular solar prominence visible to all. The video was captured with specialized equipment from New Boston, Texas, USA on April 8, 2024.

APOD: 2024 April 13 - Palm Tree Partial Eclipse
Explanation: Only those along the narrow track of the Moon's shadow on April 8 saw a total solar eclipse. But most of North America still saw a partial eclipse of the Sun. From Clearwater, Florida, USA this single snapshot captured multiple images of that more widely viewed celestial event without observing the Sun directly. In the shade of a palm tree, criss-crossing fronds are projecting recognizable eclipse images on the ground, pinhole camera style. In Clearwater the maximum eclipse phase was about 53 percent.

APOD: 2024 April 11 - Eclipse in Seven
Explanation: Start at the upper left above and you can follow the progress of April 8's total eclipse of the Sun in seven sharp, separate exposures. The image sequence was recorded with a telescope and camera located within the narrow path of totality as the Moon's shadow swept across Newport, Vermont, USA. At center is a spectacular view of the solar corona. The tenuous outer atmosphere of the Sun is only easily visible to the eye in clear dark skies during the total eclipse phase. Seen from Newport, the total phase for this solar eclipse lasted about 3 minutes and 26 seconds.

APOD: 2024 April 10 – Planets Around a Total Eclipse
Explanation: What wonders appear when the Moon blocks the Sun? For many eager observers of Monday’s total eclipse of the Sun, the suddenly dark sky included the expected corona and two (perhaps surprise) planets: Venus and Jupiter. Normally, in recent days, Venus is visible only in the morning when the Sun and Jupiter are below the horizon, while Jupiter appears bright only in the evening. On Monday, though, for well-placed observers, both planets became easily visible during the day right in line with the totally eclipsed Sun. This line was captured Monday afternoon in the featured image from Mount Nebo, Arkansas, USA, along with a line of curious observers — and a picturesque tree.

APOD: 2024 April 9 – Moon Shadow over Lake Magog
Explanation: Captured in this snapshot, the shadow of the Moon came to Lake Magog, Quebec, North America, planet Earth on April 8. For the lakeside eclipse chasers, the much anticipated total solar eclipse was a spectacle to behold in briefly dark, but clear skies. Of course Lake Magog was one of the last places to be visited by the Moon's shadow. The narrow path of totality for the 2024 total solar eclipse swept from Mexico's Pacific Coast north and eastward through the US and Canada. But a partial eclipse was visible across most of the North American continent.

APOD: 2024 April 7 – A Total Solar Eclipse over Wyoming
Explanation: Will the sky be clear enough to see the eclipse? This question is already on the minds of many North Americans hoping to see tomorrow's solar eclipse. This question was also on the mind of many people attempting to see the total solar eclipse that crossed North America in August 2017. Then, the path of total darkness shot across the mainland of the USA from coast to coast, from Oregon to South Carolina -- but, like tomorrow's event, a partial eclipse occurred above most of North America. Unfortunately, in 2017, many locations saw predominantly clouds. One location that did not was a bank of the Green River Lakes, Wyoming. Intermittent clouds were far enough away to allow the center image of the featured composite sequence to be taken, an image that shows the corona of the Sun extending out past the central dark Moon that blocks our familiar Sun. The surrounding images show the partial phases of the solar eclipse both before and after totality.

APOD: 2024 April 6 - Unwinding M51
Explanation: The arms of a grand design spiral galaxy 60,000 light-years across are unwound in this digital transformation of the magnificent 2005 Hubble Space Telescope portrait of M51. In fact, M51 is one of the original spiral nebulae, its winding arms described by a mathematical curve known as a logarithmic spiral, a spiral whose separation grows in a geometric way with increasing distance from the center. Applying logarithms to shift the pixel coordinates in the Hubble image relative to the center of M51 maps the galaxy's spiral arms into diagonal straight lines. The transformed image dramatically shows the arms themselves are traced by star formation, lined with pinkish starforming regions and young blue star clusters. Companion galaxy NGC 5195 (top) seems to alter the track of the arm in front of it though, and itself remains relatively unaffected by this unwinding of M51. Also known as the spira mirabilis, logarthimic spirals can be found in nature on all scales. For example, logarithmic spirals can also describe hurricanes, the tracks of subatomic particles in a bubble chamber and, of course, cauliflower.

APOD: 2024 April 5 - The Solar Corona Unwrapped
Explanation: Changes in the alluring solar corona are detailed in this creative composite image mapping the dynamic outer atmosphere of the Sun during two separate total solar eclipses. Unwrapped from the complete circle of the eclipsed Sun's edge to a rectangle and mirrored, the entire solar corona is shown during the 2017 eclipse (bottom) seen from Jackson Hole, Wyoming, and the 2023 eclipse from Exmouth, Western Australia. While the 2017 eclipse was near a minimum in the Sun's 11 year activity cycle, the 2023 eclipse was closer to solar maximum. The 2023 solar corona hints at the dramatically different character of the active Sun, with many streamers and pinkish prominences arising along the solar limb. Of course, the solar corona is only easily visible to the eye while standing in the shadow of the Moon.

APOD: 2024 April 4 - Comet Pons-Brooks at Night
Explanation: In dark evening skies over June Lake, northern hemisphere, planet Earth, Comet 12P/Pons-Brooks stood just above the western horizon on March 30. Its twisted turbulent ion tail and diffuse greenish coma are captured in this two degree wide telescopic field of view along with bright yellowish star Hamal also known as Alpha Arietis. Now Pons-Brooks has moved out of the northern night though, approaching perihelion on April 21. On April 8 you might still spot the comet in daytime skies. But to do it, you will have to stand in the path of totality and look away from the spectacle of an alluring solar corona and totally eclipsed Sun.

APOD: 2024 April 3 – Unusual Nebula Pa 30
Explanation: What created this unusual celestial firework? The nebula, dubbed Pa 30, appears in the same sky direction now as a bright "guest star" did in the year 1181. Although Pa 30's filaments look similar to that created by a nova (for example GK Per), and a planetary nebula (for example NGC 6751), some astronomers now propose that it was created by a rare type of supernova: a thermonuclear Type Iax, and so is (also) named SN 1181. In this model, the supernova was not the result of the detonation of a single star, but rather a blast that occurred when two white dwarf stars spiraled together and merged. The blue dot in the center is hypothesized to be a zombie star, the remnant white dwarf that somehow survived this supernova-level explosion. The featured image combines images and data obtained with infrared (WISE), visible (MDM, Pan-STARRS), and X-ray (Chandra, XMM) telescopes. Future observations and analyses may tell us more.

APOD: 2024 April 2 – Detailed View of a Solar Eclipse Corona
Explanation: Only in the fleeting darkness of a total solar eclipse is the light of the solar corona easily visible. Normally overwhelmed by the bright solar disk, the expansive corona, the sun's outer atmosphere, is an alluring sight. But the subtle details and extreme ranges in the corona's brightness, although discernible to the eye, are notoriously difficult to photograph. Pictured here, however, using multiple images and digital processing, is a detailed image of the Sun's corona taken during the April 20, 2023 total solar eclipse from Exmouth, Australia. Clearly visible are intricate layers and glowing caustics of an ever changing mixture of hot gas and magnetic fields. Bright looping prominences appear pink just around the Sun's limb. A similar solar corona might be visible through clear skies in a narrow swath across the North America during the total solar eclipse that occurs just six days from today

APOD: 2024 April 1 – Swirling Magnetic Field around Our Galaxy's Central Black Hole
Explanation: What's happening to the big black hole in the center of our galaxy? It is sucking in matter from a swirling disk -- a disk that is magnetized, it has now been confirmed. Specifically, the black hole's accretion disk has recently been seen to emit polarized light, radiation frequently associated with a magnetized source. Pictured here is a close-up of Sgr A*, our Galaxy's central black hole, taken by radio telescopes around the world participating in the Event Horizon Telescope (EHT) Collaboration. Superposed are illustrative curved lines indicating polarized light likely emitted from swirling magnetized gas that will soon fall into the 4+ million solar mass central black hole. The central part of this image is likely dark because little light-emitting gas is visible between us and the dark event horizon of the black hole. Continued EHT monitoring of this and M87's central black hole may yield new clues about the gravity of black holes and how infalling matter creates disks and jets.

APOD: 2024 March 31 – Total Solar Eclipse Below the Bottom of the World
Explanation: In late 2021 there was a total solar eclipse visible only at the end of the Earth. To capture the unusual phenomenon, airplanes took flight below the clouded seascape of Southern Ocean. The featured image shows one relatively spectacular capture where the bright spot is the outer corona of the Sun and the eclipsing Moon is seen as the dark spot in the center. A wing and engine of the airplane are visible across the left and bottom of the image, while another airplane observing the eclipse is visible on the far left. The dark area of the sky surrounding the eclipsed Sun is called a shadow cone. It is dark because you are looking down a long corridor of air shadowed by the Moon. A careful inspection of the eclipsed Sun will reveal the planet Mercury just to the right. You won't have to travel to the end of the Earth to see the next total solar eclipse. The total eclipse path will cross North America on 2024 April 8, just over one week from today.

APOD: 2024 March 30 - Medieval Astronomy from Melk Abbey
Explanation: Discovered by accident, this manuscript page provides graphical insight to astronomy in medieval times, before the Renaissance and the influence of Nicolaus Copernicus, Tycho Brahe, Johannes Kepler, and Galileo. The intriguing page is from lecture notes on astronomy compiled by the monk Magister Wolfgang de Styria before the year 1490. The top panels clearly illustrate the necessary geometry for a lunar (left) and solar eclipse in the Earth-centered Ptolemaic system. At lower left is a diagram of the Ptolemaic view of the Solar System with text at the upper right to explain the movement of the planets according to Ptolemy's geocentric model. At the lower right is a chart to calculate the date of Easter Sunday in the Julian calendar. The illustrated manuscript page was found at historic Melk Abbey in Austria.

APOD: 2024 March 23 - Ares 3 Landing Site: The Martian Revisited
Explanation: This close-up from the Mars Reconnaissance Orbiter's HiRISE camera shows weathered craters and windblown deposits in southern Acidalia Planitia. A striking shade of blue in standard HiRISE image colors, to the human eye the area would probably look grey or a little reddish. But human eyes have not gazed across this terrain, unless you count the eyes of NASA astronauts in the sci-fi novel, "The Martian", by Andy Weir. The novel chronicles the adventures of Mark Watney, an astronaut stranded at the fictional Mars mission Ares 3 landing site, corresponding to the coordinates of this cropped HiRISE frame. For scale, Watney's 6-meter-diameter habitat at the site would be about 1/10th the diameter of the large crater. Of course, the Ares 3 landing coordinates are only about 800 kilometers north of the (real life) Carl Sagan Memorial Station, the 1997 Pathfinder landing site.

APOD: 2024 March 22 - Phobos: Moon over Mars
Explanation: A tiny moon with a scary name, Phobos emerges from behind the Red Planet in this timelapse sequence from the Earth-orbiting Hubble Space Telescope. Over 22 minutes the 13 separate exposures were captured near the 2016 closest approach of Mars to planet Earth. Martians have to look to the west to watch Phobos rise, though. The small moon is closer to its parent planet than any other moon in the Solar System, about 3,700 miles (6,000 kilometers) above the Martian surface. It completes one orbit in just 7 hours and 39 minutes. That's faster than a Mars rotation, which corresponds to about 24 hours and 40 minutes. As a result, seen from the surface of Mars speeding Phobos rises above the western horizon 2 times in a Martian day. Still, Phobos is doomed.

APOD: 2024 March 21 - The Leo Trio
Explanation: This popular group leaps into the early evening sky around the March equinox and the northern hemisphere spring. Famous as the Leo Triplet, the three magnificent galaxies found in the prominent constellation Leo gather here in one astronomical field of view. Crowd pleasers when imaged with even modest telescopes, they can be introduced individually as NGC 3628 (left), M66 (bottom right), and M65 (top). All three are large spiral galaxies but tend to look dissimilar, because their galactic disks are tilted at different angles to our line of sight. NGC 3628, also known as the Hamburger Galaxy, is temptingly seen edge-on, with obscuring dust lanes cutting across its puffy galactic plane. The disks of M66 and M65 are both inclined enough to show off their spiral structure. Gravitational interactions between galaxies in the group have left telltale signs, including the tidal tails and warped, inflated disk of NGC 3628 and the drawn out spiral arms of M66. This gorgeous view of the region spans over 1 degree (two full moons) on the sky in a frame that covers over half a million light-years at the trio's estimated distance of 30 million light-years.

APOD: 2024 March 18 – Comet Pons Brooks Swirling Coma
Explanation: A bright comet will be visible during next month's total solar eclipse. This very unusual coincidence occurs because Comet 12P/Pons-Brooks's return to the inner Solar System places it by chance only 25 degrees away from the Sun during Earth's April 8 total solar eclipse. Currently the comet is just on the edge of visibility to the unaided eye, best visible with binoculars in the early evening sky toward the constellation of the Fish (Pisces). Comet Pons-Brooks, though, is putting on quite a show for deep camera images even now. The featured image is a composite of three very specific colors, showing the comet's ever-changing ion tail in light blue, its outer coma in green, and highlights some red-glowing gas around the coma in a spiral. The spiral is thought to be caused by gas being expelled by the slowly rotating nucleus of the giant iceberg comet. Although it is always difficult to predict the future brightness of comets, Comet Pons-Brook has been particularly prone to outbursts, making it even more difficult to predict how bright it will actually be as the Moon moves in front of the Sun on April 8.

APOD: 2024 March 13 – The Seagull Nebula
Explanation: A broad expanse of glowing gas and dust presents a bird-like visage to astronomers from planet Earth, suggesting its popular moniker: the Seagull Nebula. This portrait of the cosmic bird covers a 2.5-degree wide swath across the plane of the Milky Way, near the direction of Sirius, alpha star of the constellation of the Big Dog (Canis Major). Of course, the region includes objects with other catalog designations: notably NGC 2327, a compact, dusty emission and reflection nebula with an embedded massive star that forms the bird's head. Likely part of a larger shell structure swept up by successive supernova explosions, the broad Seagull Nebula is cataloged as Sh2-296 and IC 2177. The prominent bluish arc below and right of center is a bow shock from runaway star FN Canis Majoris. Dominated by the reddish glow of atomic hydrogen, this complex of gas and dust clouds with other stars of the Canis Majoris OB1 association spans over 200 light-years at the Seagull Nebula's estimated 3,800 light-year distance.

APOD: 2024 March 12 – A Galaxy Shaped Rocket Exhaust Spiral
Explanation: What's that over the horizon? What may look like a strangely nearby galaxy is actually a normal rocket's exhaust plume -- but unusually backlit. Although the SpaceX Falcon 9 rocket was launched from Vandenberg Space Force Base in California, USA, its burned propellant was visible over a much wider area, with the featured photograph being taken from Akureyri, Iceland. The huge spaceship was lifted off a week ago, and the resulting spectacle was captured soon afterward with a single 10-second smartphone exposure, before it quickly dissipated. Like noctilucent clouds, the plume's brightness is caused by the Twilight Effect, where an object is high enough to be illuminated by the twilight Sun, even when the observer on the ground experiences the darkness of night. The spiral shape is caused by the Falcon rocket reorienting to release satellites in different directions. Stars and faint green and red aurora appear in the background of this extraordinary image.

APOD: 2024 March 10 – A Total Eclipse at the End of the World
Explanation: Would you go to the end of the world to see a total eclipse of the Sun? If you did, would you be surprised to find someone else there already? In 2003, the Sun, the Moon, Antarctica, and two photographers all lined up in Antarctica during an unusual total solar eclipse. Even given the extreme location, a group of enthusiastic eclipse chasers ventured near the bottom of the world to experience the surreal momentary disappearance of the Sun behind the Moon. One of the treasures collected was the featured picture -- a composite of four separate images digitally combined to realistically simulate how the adaptive human eye saw the eclipse. As the image was taken, both the Moon and the Sun peeked together over an Antarctic ridge. In the sudden darkness, the magnificent corona of the Sun became visible around the Moon. Quite by accident, another photographer was caught in one of the images checking his video camera. Visible to his left are an equipment bag and a collapsible chair. A more easily visible solar eclipse will occur in just under four weeks and be visible from a long, thin swath of North America.

APOD: 2024 March 7 - The Crew-8 Nebula
Explanation: Not the James Webb Space Telescope's latest view of a distant galactic nebula, this cloud of gas and dust dazzled spacecoast skygazers on March 3. The telephoto snapshot was taken minutes after the launch of a Falcon 9 rocket on the SpaceX Crew-8 mission to the International Space Station. It captures plumes and exhaust from the separated first and second stages, a drifting Rorschach pattern in dark evening skies. The bright spot near bottom center within the stunning terrestrial nebulosity is the second stage engine firing to carry 4 humans to space in the Crew Dragon spacecraft Endeavour. In sharp silhouette just above it is the Falcon 9 first stage booster orienting itself for return to a landing zone at Cape Canaveral, planet Earth. This reuseable first stage booster was making its first flight. But the Crew Dragon Endeavour capsule has flown humans to low Earth orbit and back again 4 times before. Endeavour, as a name for a spacecraft, has also seen reuse, christening retired Space Shuttle Endeavour and the Apollo 15 command module.

APOD: 2024 March 5 – NGC 2170: Angel Nebula Abstract Art
Explanation: Is this a painting or a photograph? In this celestial abstract art composed with a cosmic brush, dusty nebula NGC 2170, also known as the Angel Nebula, shines just above the image center. Reflecting the light of nearby hot stars, NGC 2170 is joined by other bluish reflection nebulae, a red emission region, many dark absorption nebulae, and a backdrop of colorful stars. Like the common household items that abstract painters often choose for their subjects, the clouds of gas, dust, and hot stars featured here are also commonly found in a setting like this one -- a massive, star-forming molecular cloud in the constellation of the Unicorn (Monoceros). The giant molecular cloud, Mon R2, is impressively close, estimated to be only 2,400 light-years or so away. At that distance, this canvas would be over 60 light-years across.

APOD: 2024 February 27 – Supernova Remnant Simeis 147
Explanation: It's easy to get lost following the intricate, looping, and twisting filaments of supernova remnant Simeis 147. Also cataloged as Sharpless 2-240, the filamentary nebula goes by the popular nickname the Spaghetti Nebula. Seen toward the boundary of the constellations of the Bull (Taurus) and the Charioteer (Auriga), the impressive gas structure covers nearly 3 degrees on the sky, equivalent to 6 full moons. That's about 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. This composite image includes data taken through narrow-band filters isolating emission from hydrogen (red) and oxygen (blue) glowing gas. The supernova remnant has an estimated age of about 40,000 years, meaning light from this massive stellar explosion first reached the Earth when woolly mammoths roamed free. Besides the expanding remnant, this cosmic catastrophe left behind a pulsar, a spinning neutron star that is the remnant of the original star's core.

APOD: 2024 February 24 - Odysseus to the Moon
Explanation: Intuitive Machines' robotic lander Odysseus has accomplished the first U.S. landing on the Moon since the Apollo 17 mission in 1972. Launched on a SpaceX rocket on February 15, the phone booth sized lander reached lunar orbit on the 21st and touched down on the lunar surface at 6:23 pm ET on February 22nd. Its landing region is about 300 kilometers north of the Moon's south pole, near a crater designated Malapert A. Resting on its side, the lander is presently collecting solar power and transmitting data back to the Intuitive Machines' mission control center in Houston. The mission marks the first commercial uncrewed landing on the Moon. Prior to landing, Odysseus’ camera captured this extreme wide angle image (landing legs visible at right) as it flew over Schomberger crater some 200 kilometers from its landing site. Odysseus was still about 10 kilometers above the lunar surface.

APOD: 2024 February 19 – Looking Sideways from the Parker Solar Probe
Explanation: What's happening near the Sun? To help find out, NASA launched the robotic Parker Solar Probe (PSP) to investigate regions closer to the Sun than ever before. The PSP's looping orbit brings it nearer to the Sun each time around -- every few months. The featured time-lapse video shows the view looking sideways from behind PSP's Sun shield during its 16th approach to the Sun last year -- from well within the orbit of Mercury. The PSP's Wide Field Imager for Solar Probe (WISPR) cameras took the images over eleven days, but they are digitally compressed here into about one minute video. The waving of the solar corona is visible, as is a coronal mass ejection, with stars, planets, and even the central band of our Milky Way Galaxy streaming by in the background as the PSP orbits the Sun. PSP has found the solar neighborhood to be surprisingly complex and to include switchbacks -- times when the Sun's magnetic field briefly reverses itself.

APOD: 2024 February 18 – Hoags Object: A Nearly Perfect Ring Galaxy
Explanation: Is this one galaxy or two? This question came to light in 1950 when astronomer Arthur Hoag chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark. How Hoag's Object formed, including its nearly perfectly round ring of stars and gas, remains unknown. Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. The featured photo was taken by the Hubble Space Telescope and reprocessed using an artificially intelligent de-noising algorithm. Observations in radio waves indicate that Hoag's Object has not accreted a smaller galaxy in the past billion years. Hoag's Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens). Many galaxies far in the distance are visible toward the right, while coincidentally, visible in the gap at about seven o'clock, is another but more distant ring galaxy.

APOD: 2024 February 17 - Meteor over the Bay of Naples
Explanation: A cosmic dust grain plowing through the upper atmosphere much faster than a falling leaf created this brilliant meteor streak. In a serendipitous moment, the sublime night sky view was captured from the resort island of Capri, in the Bay of Naples, on the evening of February 8. Looking across the bay, the camera faces northeast toward the lights of Naples and surrounding cities. Pointing toward the horizon, the meteor streak by chance ends above the silhouette of Mount Vesuvius. One of planet Earth's most famous volcanos, an eruption of Mount Vesuvius destroyed the city of Pompeii in 79 AD.

APOD: 2024 February 16 - Structure in the Tail of Comet 12P/Pons-Brooks
Explanation: Heading for its next perihelion passage on April 21, Comet 12P/Pons-Brooks is growing brighter. The greenish coma of this periodic Halley-type comet has become relatively easy to observe in small telescopes. But the bluish ion tail now streaming from the active comet's coma and buffeted by the solar wind, is faint and difficult to follow. Still, in this image stacked exposures made on the night of February 11 reveal the fainter tail's detailed structures. The frame spans over two degrees across a background of faint stars and background galaxies toward the northern constellation Lacerta. Of course Comet 12P's April 21 perihelion passage will be only two weeks after the April 8 total solar eclipse, putting the comet in planet Earth's sky along with a totally eclipsed Sun.

APOD: 2024 February 15 - NGC 253: Dusty Island Universe
Explanation: Shiny NGC 253 is one of the brightest spiral galaxies visible, and also one of the dustiest. Some call it the Silver Coin Galaxy for its appearance in small telescopes, or just the Sculptor Galaxy for its location within the boundaries of the southern constellation Sculptor. Discovered in 1783 by mathematician and astronomer Caroline Herschel, the dusty island universe lies a mere 10 million light-years away. About 70 thousand light-years across, NGC 253 is the largest member of the Sculptor Group of Galaxies, the nearest to our own Local Group of Galaxies. In addition to its spiral dust lanes, tendrils of dust seem to be rising from its galactic disk laced with young star clusters and star forming regions in this colorful galaxy portrait. The high dust content accompanies frantic star formation, earning NGC 253 the designation of a starburst galaxy. NGC 253 is also known to be a strong source of high-energy x-rays and gamma rays, likely due to massive black holes near the galaxy's center.

APOD: 2024 February 12 – HFG1 & Abell 6: Planetary Nebulae
Explanation: Planetary nebulae like Heckathorn-Fesen-Gull 1 (HFG1) and Abell 6 in the constellation Cassiopeia are remnants from the last phase of a medium sized star like our Sun. In spite of their shapes, planetary nebulae have nothing in common with actual planets. Located in the bottom left part of the featured photo, HFG1 was created by the binary star system V664 Cas, which consists of a white dwarf star and a red giant star. Both stars orbit their center of mass over about half an Earth day. Traveling with the entire nebula at a speed about 300 times faster than the fastest train on Earth, V664 Cas generates a bluish arc shaped shock wave. The wave interacts most strongly with the surrounding interstellar medium in the areas where the arc is brightest. After roughly 10,000 years, planetary nebulae become invisible due to a lack of ultraviolet light being emitted by the stars that create them. Displaying beautiful shapes and structures, planetary nebulae are highly desired objects for astrophotographers.

APOD: 2024 February 10 - The Shadow of Ingenuity's Damaged Rotor Blade
Explanation: On January 18, 2024, during its 72nd flight in the thin Martian atmosphere, autonomous Mars Helicopter Ingenuity rose to an altitude of 12 meters (40 feet) and hovered for 4.5 seconds above the Red Planet. Ingenuity's 72nd landing was a rough one though. During descent it lost contact with the Perseverance rover about 1 meter above the Martian surface. Ingenuity was able to transmit this image after contact was re-established, showing the shadow of one of its rotor blades likely damaged during landing. And so, after wildly exceeding expectations during over 1,000 days of exploring Mars, the history-making Ingenuity has ended its flight operations. Nicknamed Ginny, Mars Helicopter Ingenuity became the first aircraft to achieve powered, controlled flight on another planet on April 19, 2021. Before launch, a small piece of material from the lower-left wing of the Wright Brothers Flyer 1, the first aircraft to achieve powered, controlled flight on planet Earth, was fixed to the underside of Ingenuity's solar panel.

APOD: 2024 February 9 - When Roses Aren't Red
Explanation: Not all roses are red of course, but they can still be very pretty. Likewise, the beautiful Rosette Nebula and other star forming regions are often shown in astronomical images with a predominately red hue, in part because the dominant emission in the nebula is from hydrogen atoms. Hydrogen's strongest optical emission line, known as H-alpha, is in the red region of the spectrum. But the beauty of an emission nebula need not be appreciated in red light alone. Other atoms in the nebula are also excited by energetic starlight and produce narrow emission lines as well. In this close-up view of the Rosette Nebula, narrowband images are mapped into broadband colors to show emission from Sulfur atoms in red, Hydrogen in green, and Oxygen in blue. In fact, the scheme of mapping these narrow atomic emission lines (SHO) into the broader colors (RGB) is adopted in many Hubble images of emission nebulae. This image spans about 50 light-years across the center of the Rosette Nebula. The nebula lies some 3,000 light-years away in the constellation Monoceros.

APOD: 2024 February 8 - Globular Star Cluster 47 Tuc
Explanation: Globular star cluster 47 Tucanae is a jewel of the southern sky. Also known as NGC 104, it roams the halo of our Milky Way Galaxy along with some 200 other globular star clusters. The second brightest globular cluster (after Omega Centauri) as seen from planet Earth, 47 Tuc lies about 13,000 light-years away. It can be spotted with the naked-eye close on the sky to the Small Magellanic Cloud in the constellation of the Toucan. The dense cluster is made up of hundreds of thousands of stars in a volume only about 120 light-years across. Red giant stars on the outskirts of the cluster are easy to pick out as yellowish stars in this sharp telescopic portrait. Tightly packed globular cluster 47 Tuc is also home to a star with the closest known orbit around a black hole.

APOD: 2024 February 5 – In the Core of the Carina Nebula
Explanation: What's happening in the core of the Carina Nebula? Stars are forming, dying, and leaving an impressive tapestry of dark dusty filaments. The entire Carina Nebula, cataloged as NGC 3372, spans over 300 light years and lies about 8,500 light-years away in the constellation of Carina. The nebula is composed predominantly of hydrogen gas, which emits the pervasive red and orange glows seen mostly in the center of this highly detailed featured image. The blue glow around the edges is created primarily by a trace amount of glowing oxygen. Young and massive stars located in the nebula's center expel dust when they explode in supernovas. Eta Carinae, the most energetic star in the nebula's center, was one of the brightest stars in the sky in the 1830s, but then faded dramatically.

APOD: 2024 February 4 – The Cone Nebula from Hubble
Explanation: Stars are forming in the gigantic dust pillar called the Cone Nebula. Cones, pillars, and majestic flowing shapes abound in stellar nurseries where natal clouds of gas and dust are buffeted by energetic winds from newborn stars. The Cone Nebula, a well-known example, lies within the bright galactic star-forming region NGC 2264. The Cone was captured in unprecedented detail in this close-up composite of several observations from the Earth-orbiting Hubble Space Telescope. While the Cone Nebula, about 2,500 light-years away in Monoceros, is around 7 light-years long, the region pictured here surrounding the cone's blunted head is a mere 2.5 light-years across. In our neck of the galaxy that distance is just over half way from our Sun to its nearest stellar neighbors in the Alpha Centauri star system. The massive star NGC 2264 IRS, seen by Hubble's infrared camera in 1997, is the likely source of the wind sculpting the Cone Nebula and lies off the top of the image. The Cone Nebula's reddish veil is produced by dust and glowing hydrogen gas.

APOD: 2024 February 2 - NGC 1893 and the Tadpoles of IC 410
Explanation: This cosmic view shows off an otherwise faint emission nebula IC 410, captured under clear Netherlands skies with telescope and narrowband filters. Above and right of center you can spot two remarkable inhabitants of the interstellar pond of gas and dust, known as the tadpoles of IC 410. Partly obscured by foreground dust, the nebula itself surrounds NGC 1893, a young galactic cluster of stars. Formed in the interstellar cloud a mere 4 million years ago, the intensely hot, bright cluster stars energize the glowing gas. Globules composed of denser cooler gas and dust, the tadpoles are around 10 light-years long and are likely sites of ongoing star formation. Sculpted by stellar winds and radiation their heads are outlined by bright ridges of ionized gas while their tails trail away from the cluster's central young stars. IC 410 and embedded NGC 1893 lie some 10,000 light-years away, toward the nebula-rich constellation Auriga.

APOD: 2024 January 29 – The Pleiades: Seven Dusty Sisters
Explanation: The well-known Pleiades star cluster is slowly destroying part of a passing cloud of gas and dust. The Pleiades is the brightest open cluster of stars on Earth's sky and can be seen from almost any northerly location with the unaided eye. Over the past 100,000 years, a field of gas and dust is moving by chance right through the Pleiades star cluster and is causing a strong reaction between the stars and dust. The passing cloud might be part of the Radcliffe wave, a newly discovered structure of gas and dust connecting several regions of star formation in the nearby part of our Milky Way galaxy. Pressure from the stars' light significantly repels the dust in the surrounding blue reflection nebula, with smaller dust particles being repelled more strongly. A short-term result is that parts of the dust cloud have become filamentary and stratified. The featured deep image incorporates nearly 9 hours of exposure and was captured from Utah Desert Remote Observatory in Utah, USA, last year.

APOD: 2024 January 25 - Jyväskylä in the Sky
Explanation: You might not immediately recognize this street map of a neighborhood in Jyväskylä, Finland, planet Earth. But that's probably because the map was projected into the night sky and captured with an allsky camera on January 16. The temperature recorded on that northern winter night was around minus 20 degrees Celsius. As ice crystals formed in the atmosphere overhead, street lights spilling illumination into the sky above produced visible light pillars, their ethereal appearance due to specular reflections from the fluttering crystals' flat surfaces. Of course, the projected light pillars trace a map of the brightly lit local streets, though reversed right to left in the upward looking camera's view. This light pillar street map was seen to hover for hours in the Jyväskylä night.

APOD: 2024 January 23 – Deep Nebulas: From Seagull to California
Explanation: How well do you know the night sky? OK, but how well can you identify famous sky objects in a very deep image? Either way, here is a test: see if you can find some well-known night-sky icons in a deep image filled with faint nebulosity. This image contains the Pleiades star cluster, Barnard's Loop, Horsehead Nebula, Orion Nebula, Rosette Nebula, Cone Nebula, Rigel, Jellyfish Nebula, Monkey Head Nebula, Flaming Star Nebula, Tadpole Nebula, Aldebaran, Simeis 147, Seagull Nebula and the California Nebula. To find their real locations, here is an annotated image version. The reason this task might be difficult is similar to the reason it is initially hard to identify familiar constellations in a very dark sky: the tapestry of our night sky has an extremely deep hidden complexity. The featured composite reveals some of this complexity in a mosaic of 28 images taken over 800 hours from dark skies over Arizona, USA.

APOD: 2024 January 22 – Shadows of Mountain and Moon
Explanation: Can the Moon and a mountain really cast similar shadows? Yes, but the division between light and dark does not have to be aligned. Pictured, a quarter moon was captured above the mountain Grivola in Italy in early October of 2022. The Sun is to the right of the featured picturesque landscape, illuminating the right side of the Moon in a similar way that it illuminates the right side of the mountain. This lunar phase is called "quarter", in part, because the lit fraction visible from Earth is one quarter of the entire lunar surface. Digital post-processing of this single exposure gave both gigantic objects more prominence. Capturing the terminator of this quarter moon in close alignment with nearly vertical mountain ridge required careful timing because the Earth rotates once a day.

APOD: 2024 January 20 - Falcon Heavy Boostback Burn
Explanation: The December 28 night launch of a Falcon Heavy rocket from Kennedy Space Center in Florida marked the fifth launch for the rocket's reusable side boosters. About 2 minutes 20 seconds into the flight, the two side boosters separated from the rocket's core stage. Starting just after booster separation, this three minute long exposure captures the pair's remarkable boostback burns, maneuvers executed prior to their return to landing zones on planet Earth. While no attempt was made to recover the Falcon Heavy's core stage, both side boosters landed successfully and can be flown again. The four previous flights for these side boosters included last October's launch of NASA's asteroid-bound Psyche mission. Their next planned flight is on the Europa Clipper mission scheduled for launch in October 2024.

APOD: 2024 January 18 - Northern Lights from the Stratosphere
Explanation: Northern lights shine in this night skyview from planet Earth's stratosphere, captured on January 15. The single, 5 second exposure was made with a hand-held camera on board an aircraft above Winnipeg, Canada. During the exposure, terrestrial lights below leave colorful trails along the direction of motion of the speeding aircraft. Above the more distant horizon, energetic particles accelerated along Earth's magnetic field at the planet's polar regions excite atomic oxygen to create the shimmering display of Aurora Borealis. The aurora's characteristic greenish hue is generated at altitudes of 100-300 kilometers and red at even higher altitudes and lower atmospheric densities. The luminous glow of faint stars along the plane of our Milky Way galaxy arcs through the night, while the Andromeda galaxy extends this northern skyview to extragalactic space. A diffuse hint of Andromeda, the closest large spiral to the Milky Way, can just be seen to the upper left.

APOD: 2024 January 13 - Circling the Sun
Explanation: Earth's orbit around the Sun is not a circle, it's an ellipse. The point along its elliptical orbit where our fair planet is closest to the Sun is called perihelion. This year, perihelion was on January 2 at 01:00 UTC, with the Earth about 3 million miles closer to the Sun than it was at aphelion (last July 6), the farthest point in its elliptical orbit. Of course, distance from the Sun doesn't determine the seasons, and it doesn't the determine size of Sun halos. Easier to see with the Sun hidden behind a tall tree trunk, this beautiful ice halo forms a 22 degree-wide circle around the Sun, recorded while strolling through the countryside near Heroldstatt, Germany. The Sun halo's 22 degree angular diameter is determined by the six-sided geometry of water ice crystals drifting high in planet Earth's atmosphere.

APOD: 2024 January 11 - Quadrantids of the North
Explanation: Named for a forgotten constellation, the Quadrantid Meteor Shower puts on an annual show for planet Earth's northern hemisphere skygazers. The shower's radiant on the sky lies within the old, astronomically obsolete constellation Quadrans Muralis. That location is not far from the Big Dipper asterism, known to some as the Plough, at the boundaries of the modern constellations Bootes and Draco. The Big Dipper "handle" stars are near the upper right corner in this frame, with the meteor shower radiant just below. North star Polaris is toward the top left. Pointing back toward the radiant, Quadrantid meteors streak through the night in this skyscape from Jangsu, South Korea. The composite image was recorded in the hours around the shower's peak on January 4, 2024. A likely source of the dust stream that produces Quadrantid meteors was identified in 2003 as an asteroid.

APOD: 2024 January 8 – The Phases of Venus
Explanation: Venus goes through phases. Just like our Moon, Venus can appear as a full circular disk, a thin crescent, or anything in between. Venus, frequently the brightest object in the post-sunset or pre-sunrise sky, appears so small, however, that it usually requires binoculars or a small telescope to clearly see its current phase. The featured time-lapse sequence was taken over the course of six months in 2015 from Surgères, Charente-Maritime, France, and shows not only how Venus changes phase, but changes angular size as well. When Venus is on the far side of the Sun from the Earth, it appears angularly smallest and nearest to full phase, while when Venus and Earth are on the same side of the Sun, Venus appears larger, but as a crescent. This month Venus rises before dawn in waxing gibbous phases.

APOD: 2024 January 6 - The Snows of Churyumov-Gerasimenko
Explanation: You couldn't really be caught in this blizzard while standing by a cliff on periodic comet 67P/Churyumov-Gerasimenko. Orbiting the comet in June of 2016, the Rosetta spacecraft's narrow angle camera did record streaks of dust and ice particles similar to snow as they drifted across the field of view close to the camera and above the comet's surface. Still, some of the bright specks in the scene are likely due to a rain of energetic charged particles or cosmic rays hitting the camera, and the dense background of stars in the direction of the constellation of the Big Dog (Canis Major). In the video, the background stars are easy to spot trailing from top to bottom. The stunning movie was constructed from 33 consecutive images taken over 25 minutes while Rosetta cruised some 13 kilometers from the comet's nucleus. In September 2016, the nucleus became the final resting place for the Rosetta spacecraft after its mission was ended with a successful controlled impact on 67P/Churyumov-Gerasimenko.

APOD: 2024 January 1 – NGC 1232: A Grand Design Spiral Galaxy
Explanation: Galaxies are fascinating not only for what is visible, but for what is invisible. Grand spiral galaxy NGC 1232, captured in detail by one of the Very Large Telescopes, is a good example. The visible is dominated by millions of bright stars and dark dust, caught up in a gravitational swirl of spiral arms revolving about the center. Open clusters containing bright blue stars can be seen sprinkled along these spiral arms, while dark lanes of dense interstellar dust can be seen sprinkled between them. Less visible, but detectable, are billions of dim normal stars and vast tracts of interstellar gas, together wielding such high mass that they dominate the dynamics of the inner galaxy. Leading theories indicate that even greater amounts of matter are invisible, in a form we don't yet know. This pervasive dark matter is postulated, in part, to explain the motions of the visible matter in the outer regions of galaxies.