Astronomy Picture of the Day Search Results for "nursery OR creation OR birth"

APOD: 2024 April 19 - The Great Carina Nebula
Explanation: A jewel of the southern sky, the Great Carina Nebula is more modestly known as NGC 3372. One of our Galaxy's largest star forming regions, it spans over 300 light-years. Like the smaller, more northerly Great Orion Nebula, the Carina Nebula is easily visible to the unaided eye. But at a distance of 7,500 light-years it lies some 5 times farther away. This stunning telescopic view reveals remarkable details of the region's glowing filaments of interstellar gas and obscuring cosmic dust clouds. The Carina Nebula is home to young, extremely massive stars, including the still enigmatic variable Eta Carinae, a star with well over 100 times the mass of the Sun. Eta Carinae is the bright star above the central dark notch in this field and left of the dusty Keyhole Nebula (NGC 3324).

APOD: 2024 February 20 – AM1054: Stars Form as Galaxies Collide
Explanation: When galaxies collide, how many stars are born? For AM1054-325, featured here in a recently released image by the Hubble Space Telescope, the answer is millions. Instead of stars being destroyed as galaxy AM1054-325 and a nearby galaxy circle each other, their gravity and motion has ignited stellar creation. Star formation occurs rapidly in the gaseous debris stretching from AM1054-325’s yellowish body due to the other galaxy’s gravitational pull. Hydrogen gas surrounding newborn stars glows pink. Bright infant stars shine blue and cluster together in compact nurseries of thousands to millions of stars. AM1054-325 possesses over 100 of these intense-blue, dot-like star clusters, some appearing like a string of pearls. Analyzing ultraviolet light helped determine that most of these stars are less than 10 million years old: stellar babies. Many of these nurseries may grow up to be globular star clusters, while the bundle of young stars at the bottom tip may even detach and form a small galaxy.

APOD: 2024 January 16 – The Orion You Can Almost See
Explanation: Do you recognize this constellation? Although it is one of the most recognizable star groupings on the sky, this is a more full Orion than you can see -- an Orion only revealed with long exposure digital camera imaging and post- processing. Here the cool red giant Betelgeuse takes on a strong orange tint as the brightest star on the upper left. Orion's hot blue stars are numerous, with supergiant Rigel balancing Betelgeuse on the lower right, and Bellatrix at the upper right. Lined up in Orion's belt are three stars all about 1,500 light-years away, born from the constellation's well-studied interstellar clouds. Just below Orion's belt is a bright but fuzzy patch that might also look familiar -- the stellar nursery known as Orion's Nebula. Finally, just barely visible to the unaided eye but quite striking here is Barnard's Loop -- a huge gaseous emission nebula surrounding Orion's Belt and Nebula discovered over 100 years ago by the pioneering Orion photographer E. E. Barnard.

APOD: 2023 July 23 – The Antikythera Mechanism
Explanation: It does what? No one knew that 2,000 years ago, the technology existed to build such a device. The Antikythera mechanism, pictured, is now widely regarded as the first computer. Found at the bottom of the sea aboard a decaying Greek ship, its complexity prompted decades of study, and even today some of its functions likely remain unknown. X-ray images of the device, however, have confirmed that a main function of its numerous clock-like wheels and gears is to create a portable, hand-cranked, Earth-centered, orrery of the sky, predicting future star and planet locations as well as lunar and solar eclipses. The corroded core of the Antikythera mechanism's largest gear is featured, spanning about 13 centimeters, while the entire mechanism was 33 centimeters high, making it similar in size to a large book. Recently, modern computer modeling of missing components is allowing for the creation of a more complete replica of this surprising ancient machine.

APOD: 2023 June 14 – The Shark Nebula
Explanation: There is no sea on Earth large enough to contain the Shark nebula. This predator apparition poses us no danger as it is composed only of interstellar gas and dust. Dark dust like that featured here is somewhat like cigarette smoke and created in the cool atmospheres of giant stars. After being expelled with gas and gravitationally recondensing, massive stars may carve intricate structures into their birth cloud using their high energy light and fast stellar winds as sculpting tools. The heat they generate evaporates the murky molecular cloud as well as causing ambient hydrogen gas to disperse and glow red. During disintegration, we humans can enjoy imagining these great clouds as common icons, like we do for water clouds on Earth. Including smaller dust nebulae such as Lynds Dark Nebula 1235 and Van den Bergh 149 & 150, the Shark nebula spans about 15 light years and lies about 650 light years away toward the constellation of the King of Aethiopia (Cepheus).

APOD: 2023 April 22 - NGC 1333: Stellar Nursery in Perseus
Explanation: In visible light NGC 1333 is seen as a reflection nebula, dominated by bluish hues characteristic of starlight reflected by interstellar dust. A mere 1,000 light-years distant toward the heroic constellation Perseus, it lies at the edge of a large, star-forming molecular cloud. This Hubble Space Telescope close-up frames a region just over 1 light-year wide at the estimated distance of NGC 1333. It shows details of the dusty region along with telltale hints of contrasty red emission from Herbig-Haro objects, jets and shocked glowing gas emanating from recently formed stars. In fact, NGC 1333 contains hundreds of stars less than a million years old, most still 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. Hubble's stunning image of the stellar nursery was released to celebrate the 33rd anniversary of the space telescope's launch.

APOD: 2023 March 20 – M1: The Expanding Crab Nebula
Explanation: Are your eyes good enough to see the Crab Nebula expand? The Crab Nebula is cataloged as M1, the first on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, an expanding cloud of debris from the explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across today, the nebula is still expanding at a rate of over 1,000 kilometers per second. Over the past decade, its expansion has been documented in this stunning time-lapse movie. In each year from 2008 to 2022, an image was produced with the same telescope and camera from a remote observatory in Austria. The sharp, processed frames even reveal the dynamic energetic emission surrounding the rapidly spinning pulsar at the center. The Crab Nebula lies about 6,500 light-years away toward the constellation of the Bull (Taurus).

APOD: 2023 March 10 - Orion and the Running Man
Explanation: Few cosmic vistas excite the imagination like The Great Nebula in Orion. Visible as a faint celestial smudge to the naked-eye, the nearest large star-forming region sprawls across this sharp telescopic image, recorded on a cold January night in dark skies from West Virginia, planet Earth. Also known as M42, the Orion Nebula's glowing gas surrounds hot, young stars. About 40 light-years across, it lies at the edge of an immense interstellar molecular cloud only 1,500 light-years away within the same spiral arm of our Milky Way galaxy as the Sun. Along with dusty bluish reflection nebula NGC 1977 and friends near the top of the frame, the eye-catching nebulae represent only a small fraction of our galactic neighborhood's wealth of star-forming material. Within the well-studied stellar nursery, astronomers have also identified what appear to be numerous infant solar systems.

APOD: 2023 January 8 – Where Your Elements Came From
Explanation: The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe. The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen. Much of the iron in your body was made during supernovas of stars that occurred long ago and far away. The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts or gravitational wave events. Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life. The featured periodic table is color coded to indicate humanity's best guess as to the nuclear origin of all known elements. The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research.

APOD: 2022 December 6 - M16: A Star Forming Pillar from Webb
Explanation: What’s happening inside this interstellar mountain? Stars are forming. The mountain is actually a column of gas and dust in the picturesque Eagle Nebula (M16). A pillar like this is so low in density that you could easily fly though it -- it only appears solid because of its high dust content and great depth. The glowing areas are lit internally by newly formed stars. These areas shine in red and infrared light because blue light is scattered away by intervening interstellar dust. The featured image was captured recently in near-infrared light in unprecedented detail by the James Webb Space Telescope (JWST), launched late last year. Energetic light, abrasive winds, and final supernovas from these young stars will slowly destroy this stellar birth column over the next 100,000 years.

APOD: 2022 October 29 - LDN 673: Dark Clouds in Aquila
Explanation: Part of a dark expanse that splits the crowded plane of our Milky Way galaxy, the Aquila Rift arcs through planet Earth's skies near bright star Altair. In eerie silhouette against the Milky Way's faint starlight, its dusty molecular clouds likely contain raw material to form hundreds of thousands of stars and astronomers search the dark clouds for telltale signs of star birth. This telescopic close-up looks toward the region at a fragmented Aquila dark cloud complex identified as LDN 673, stretching across a field of view slightly wider than the full moon. In the scene, visible indications of energetic outflows associated with young stars include the small red tinted nebulosity RNO 109 above and right of center, and Herbig-Haro object HH32 below. These dark clouds might look scary, but they're estimated to be some 600 light-years away. At that distance, this field of view spans about 7 light-years.

APOD: 2022 October 20 - Pillars of Creation
Explanation: A now famous picture from the Hubble Space Telescope featured these star forming columns of cold gas and dust light-years long inside M16, the Eagle Nebula, dubbed the Pillars of Creation. This James Webb Space Telescope NIRCam image expands Hubble's exploration of that region in greater detail and depth inside the iconic stellar nursery. Particularly stunning in Webb's near infrared view is the telltale reddish emission from knots of material undergoing gravitational collapse to form stars within the natal clouds. The Eagle Nebula is some 6,500 light-years distant. The larger bright emission nebula is itself an easy target for binoculars or small telescopes. M16 lies along the plane of our Milky Way galaxy in a nebula rich part of the sky, toward the split constellation Serpens Cauda (the tail of the snake).

APOD: 2022 October 15 - GRB 221009A
Explanation: Gamma-ray burst GRB 221009A likely signals the birth of a new black hole, formed at the core of a collapsing star long ago in the distant universe. The extremely powerful blast is depicted in this animated gif constructed using data from the Fermi Gamma Ray Space Telescope. Fermi captured the data at gamma-ray energies, detecting photons with over 100 million electron volts. In comparison visible light photons have energies of about 2 electron volts. A steady, high energy gamma-ray glow from the plane of our Milky Way galaxy runs diagonally through the 20 degree wide frame at the left, while the transient gamma-ray flash from GRB 221009A appears at center and then fades. One of the brightest gamma-ray bursts ever detected GRB 221009A is also close as far as gamma-ray bursts go, but still lies about 2 billion light-years away. In low Earth orbit Fermi’s Large Area Telescope recorded gamma-ray photons from the burst for more than 10 hours as high-energy radiation from GRB 221009A swept over planet Earth last Sunday, October 9.

APOD: 2022 September 25 - The Fairy of Eagle Nebula
Explanation: The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains, the statuesque pillars that remain might be imagined as mythical beasts. Featured here is one of several striking dust pillars of the Eagle Nebula that might be described as a gigantic alien fairy. This fairy, however, is ten light years tall and spews radiation much hotter than common fire. The greater Eagle Nebula, M16, is actually a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars. This great pillar, which is about 7,000 light years away, will likely evaporate away in about 100,000 years. The featured image is in scientifically re-assigned colors and was taken by the Earth-orbiting Hubble Space Telescope.

APOD: 2022 August 27 - IC 5146: The Cocoon Nebula
Explanation: Inside the Cocoon Nebula is a newly developing cluster of stars. Cataloged as IC 5146, the beautiful nebula is nearly 15 light-years wide. Soaring high in northern summer night skies, it's located some 4,000 light years away toward the constellation Cygnus the Swan. Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by young, hot stars, and dust-reflected starlight at the edge of an otherwise invisible molecular cloud. In fact, the bright star found near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it clears out a cavity in the molecular cloud's star forming dust and gas. A 29 hour long integration with a small telescope from Ayr, Ontario, Canada resulted in this exceptionally deep color view tracing tantalizing features within and surrounding the dusty stellar nursery.

APOD: 2022 August 12 - Portrait of the Eagle Nebula
Explanation: A star cluster around 2 million years young surrounded by natal clouds of dust and glowing gas, Messier 16 (M16) is also known as The Eagle Nebula. This beautifully detailed image of the region adopts the colorful Hubble palette and includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the ridge of bright emission left of center is another dusty starforming column known as the Fairy of Eagle Nebula. M16 lies about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake). As framed, this telescopic portrait of the Eagle Nebula is about 70 light-years across.

APOD: 2022 July 19 - Pleiades over Half Dome
Explanation: Stars come in bunches. The most famous bunch of stars on the sky is the Pleiades, a bright cluster that can be easily seen with the unaided eye. The Pleiades lies only about 450 light years away, formed about 100 million years ago, and will likely last about another 250 million years. Our Sun was likely born in a star cluster, but now, being about 4.5 billion years old, its stellar birth companions have long since dispersed. The Pleiades star cluster is pictured over Half Dome, a famous rock structure in Yosemite National Park in California, USA. The featured image is a composite of 28 foreground exposures and 174 images of the stellar background, all taken from the same location and by the same camera on the same night in October 2019. After calculating the timing of a future juxtaposition of the Pleiades and Half Dome, the astrophotrographer was unexpectedly rewarded by an electrical blackout, making the background sky unusually dark.

APOD: 2021 November 11 - NGC 1333: Stellar Nursery in Perseus
Explanation: NGC 1333 is seen in visible light as a reflection nebula, dominated by bluish hues characteristic of starlight reflected by interstellar dust. A mere 1,000 light-years distant toward the heroic constellation Perseus, it lies at the edge of a large, star-forming molecular cloud. This telescopic close-up spans about two full moons on the sky or just over 15 light-years at the estimated distance of NGC 1333. It shows details of the dusty region along with telltale hints of contrasty red emission from Herbig-Haro objects, jets and shocked glowing gas emanating from recently formed stars. In fact, NGC 1333 contains hundreds of stars less than a million years old, most still 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: 2021 September 9 - M16 Close Up
Explanation: A star cluster around 2 million years young surrounded by natal clouds of dust and glowing gas, M16 is also known as The Eagle Nebula. This beautifully detailed image of the region adopts the colorful Hubble palette and includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the ridge of bright emission left of center is another dusty starforming column known as the Fairy of Eagle Nebula. M16 lies about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).

APOD: 2021 April 17 - Inside the Flame Nebula
Explanation: The Flame Nebula is a stand out in optical images of the dusty, crowded star forming regions toward Orion's belt and the easternmost belt star Alnitak, a mere 1,400 light-years away. Alnitak is the bright star at the right edge of this infrared image from the Spitzer Space Telescope. About 15 light-years across, the infrared view takes you inside the nebula's glowing gas and obscuring dust clouds though. It reveals many stars of the recently formed, embedded cluster NGC 2024 concentrated near the center. The stars of NGC 2024 range in age from 200,000 years to 1.5 million years young. In fact, data indicate that the youngest stars are concentrated near the middle of the Flame Nebula cluster. That's the opposite of the simplest models of star formation for a stellar nursery that predict star formation begins in the denser center of a molecular cloud core. The result requires a more complex model for star formation inside the Flame Nebula.

APOD: 2021 March 21 - The Antikythera Mechanism
Explanation: No one knew that 2,000 years ago, the technology existed to build such a device. The Antikythera mechanism, pictured, is now widely regarded as the first computer. Found at the bottom of the sea aboard a decaying Greek ship, its complexity prompted decades of study, and even today some of its functions likely remain unknown. X-ray images of the device, however, have confirmed that a main function of its numerous clock-like wheels and gears is to create a portable, hand-cranked, Earth-centered, orrery of the sky, predicting future star and planet locations as well as lunar and solar eclipses. The corroded core of the Antikythera mechanism's largest gear is featured, spanning about 13 centimeters, while the entire mechanism was 33 centimeters high, making it similar in size to a large book. Recently, modern computer modeling of missing components is allowing for the creation of a more complete replica of this surprising ancient machine.

APOD: 2021 March 19 - Central Lagoon in Infrared
Explanation: Stars fill this infrared view, spanning 4 light-years across the center of the Lagoon Nebula. Visible light images show the glowing gas and obscuring dust clouds that dominate the scene. But this infrared image, constructed from Hubble Space Telescope data, peers closer to the heart of the active star-forming region revealing newborn stars scattered within, against a crowded field of background stars toward the center of our Milky Way galaxy. This tumultuous stellar nursery's central regions are sculpted and energized by the massive, young Herschel 36, seen as the bright star near center in the field of view. Herschel 36 is actually a multiple system of massive stars. At over 30 times the mass of the Sun and less than 1 million years old, the most massive star in the system should live to a stellar old age of 5 million years. Compare that to the almost 5 billion year old Sun which will evolve into a red giant in only another 5 billion years or so. The Lagoon Nebula, also known as M8, lies about 4,000 light-years away within the boundaries of the constellation Sagittarius.

APOD: 2020 December 25 - Northern Winter Night
Explanation: Orion always seems to come up sideways on northern winter evenings. Those familiar stars of the constellation of the Hunter are caught above the trees in this colorful night skyscape. Not a star at all but still visible to eye, the Great Nebula of Orion shines below the Hunter's belt stars. The camera's exposure reveals the stellar nursery's faint pinkish glow. Betelgeuse, giant star at Orion's shoulder, has the color of warm and cozy terrestrial lighting, but so does another familiar stellar giant, Aldebaran. Alpha star of the constellation Taurus the Bull, Aldebaran anchors the recognizable V-shape traced by the Hyades Cluster toward the top of the starry frame.

APOD: 2020 December 6 - M16: Pillars of Star Creation
Explanation: These dark pillars may look destructive, but they are creating stars. This pillar-capturing image of the inside of the Eagle Nebula, taken with the Hubble Space Telescope in 1995, shows 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 pillars' 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. The pillars of creation have been imaged more recently in infrared light by Hubble, NASA's Spitzer Space Telescope, and ESA's Herschel Space Observatory -- showing new detail.

APOD: 2020 November 26 - The Great Turkey Nebula
Explanation: Surprisingly reminiscent of The Great Nebula in Orion, The Great Turkey Nebula spans this creative field of view. Of course if it were the Orion Nebula it would be our closest large stellar nursery, found at the edge of a large molecular cloud a mere 1,500 light-years away. Also known as M42, the Orion Nebula is visible to the eye as the middle "star" in the sword of Orion the Hunter, a constellation now rising in planet Earth's evening skies. Stellar winds from clusters of newborn stars scattered throughout the Orion Nebula sculpt its ridges and cavities seen in familiar in telescopic images. Much larger than any bird you might be cooking, this Great Turkey Nebula was imagined to be similar in size to the Orion Nebula, about 13 light-years across. Stay safe and well.

APOD: 2020 August 28 - The Valley of Orion
Explanation: This exciting and unfamiliar view of the Orion Nebula is a visualization based on astronomical data and movie rendering techniques. Up close and personal with a famous stellar nursery normally seen from 1,500 light-years away, the digitally modeled frame transitions from a visible light representation based on Hubble data on the left to infrared data from the Spitzer Space Telescope on the right. The perspective at the center looks along a valley over a light-year wide, in the wall of the region's giant molecular cloud. Orion's valley ends in a cavity carved by the energetic winds and radiation of the massive central stars of the Trapezium star cluster. The single frame is part of a multiwavelength, three-dimensional video that lets the viewer experience an immersive, three minute flight through the Great Nebula of Orion.

APOD: 2019 November 15 - M16 and the Eagle Nebula
Explanation: A star cluster around 2 million years young surrounded by natal clouds of dust and glowing gas, M16 is also known as The Eagle Nebula. This beautifully detailed portrait of the region was made with groundbased narrow and broadband image data. It includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the ridge of bright emission at lower left is another dusty starforming column known as the Fairy of Eagle Nebula. M16 lies about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).

APOD: 2019 November 2 - Inside the Flame Nebula
Explanation: The Flame Nebula stands out in this optical image of the dusty, crowded star forming regions toward Orion's belt, a mere 1,400 light-years away. X-ray data from the Chandra Observatory and infrared images from the Spitzer Space Telescope can take you inside the glowing gas and obscuring dust clouds though. Swiping your cursor (or clicking the image) will reveal many stars of the recently formed, embedded cluster NGC 2024, ranging in age from 200,000 years to 1.5 million years young. The X-ray/infrared composite image overlay spans about 15 light-years across the Flame's center. The X-ray/infrared data also indicate that the youngest stars are concentrated near the middle of the Flame Nebula cluster. That's the opposite of the simplest models of star formation for the stellar nursery that predict star formation begins in the denser center of a molecular cloud core. The result requires a more complex model; perhaps star formation continues longer in the center, or older stars are ejected from the center due to subcluster mergers.

APOD: 2019 August 31 - Spitzer's Orion
Explanation: Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. Spanning about 40 light-years across the region, this infrared image from the Spitzer Space Telescope was constructed from data intended to monitor the brightness of the nebula's young stars, many still surrounded by dusty, planet-forming disks. Orion's young stars are only about 1 million years old, compared to the Sun's age of 4.6 billion years. The region's hottest stars are found in the Trapezium Cluster, the brightest cluster near picture center. Launched into orbit around the Sun on August 25, 2003 Spitzer's liquid helium coolant ran out in May 2009. The infrared space telescope continues to operate though, its mission scheduled to end on January 30, 2020. Recorded in 2010, this false color view is from two channels that still remain sensitive to infrared light at Spitzer's warmer operating temperatures.

APOD: 2019 August 21 - The Orion You Can Almost See
Explanation: Do you recognize this constellation? Although it is one of the most recognizable star groupings on the sky, this is a more full Orion than you can see -- an Orion only revealed with long exposure digital camera imaging and post-processing. Here the cool red giant Betelgeuse takes on a strong orange tint as the brightest star at the lower left. Orion's hot blue stars are numerous, with supergiant Rigel balancing Betelgeuse on the upper right, and Bellatrix at the upper left. Lined up in Orion's belt are three stars all about 1,500 light-years away, born from the constellation's well-studied interstellar clouds. To the right of Orion's belt is a bright but fuzzy patch that might also look familiar -- the stellar nursery known as Orion's Nebula. Finally, just barely visible to the unaided eye but quite striking here is Barnard's Loop -- a huge gaseous emission nebula surrounding Orion's Belt and Nebula discovered over 100 years ago by the pioneering Orion photographer E. E. Barnard.

APOD: 2019 August 10 - M16 Close Up
Explanation: A star cluster around 2 million years young surrounded by natal clouds of dust and glowing gas, M16 is also known as The Eagle Nebula. This beautifully detailed image of the region adopts the colorful Hubble palette and includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the ridge of bright emission left of center is another dusty starforming column known as the Fairy of Eagle Nebula. M16 lies about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).

APOD: 2019 July 28 - The North America Nebula in Infrared
Explanation: The North America Nebula can do what most North Americans cannot -- form stars. Precisely where in the nebula these stars are forming has been mostly obscured by some of the nebula's thick dust that is opaque to visible light. However, a view of the North America Nebula in infrared light by the orbiting Spitzer Space Telescope has peered through much of the dust and uncovered thousands of newly formed stars. Rolling your cursor over the above scientifically-colored infrared image will bring up a corresponding optical image of the same region for comparison. The infrared image neatly captures young stars in many stages of formation, from being imbedded in dense knots of gas and dust, to being surrounded by disks and emitted jets, to being clear of their birth cocoons. The North America Nebula (NGC 7000) spans about 50 light years and lies about 1,500 light years away toward the constellation of the Swan (Cygnus). Still, of all the stars known in the North America Nebula, which massive stars emit the energetic light that gives the ionized red glow is still debated.

APOD: 2019 April 26 - Southern Cross to Eta Carinae
Explanation: Tracking along the southern Milky Way this beautiful celestial mosaic was recorded under dark Brazilian skies. Spanning some 20 degrees it actually starts with the dark expanse of the Coalsack nebula at the lower left, tucked under an arm of the Southern Cross. That compact constellation is topped by bright yellowish Gamma Crucis, a cool giant star a mere 88 light-years distant. A line from Gamma Crucis through the blue star at the bottom of the cross, Alpha Crucis, points toward the South Celestial Pole. Follow the Milky Way to the right and your gaze will sweep across IC 2948, popularly known as the Running Chicken nebula, before it reaches Eta Carinae and the Carina Nebula near the right edge of the frame. About 200 light-years across, the Carina Nebula is a star forming region much larger than the more northerly stellar nursery the Orion Nebula. The Carina Nebula lies around 7,500 light-years from Earth along the plane of the Milky Way.

APOD: 2019 April 12 - A Cosmic Rose: The Rosette Nebula in Monoceros
Explanation: The Rosette Nebula, NGC 2237, is not the only cosmic cloud of gas and dust to evoke the imagery of flowers, but it is the most famous. At the edge of a large molecular cloud in Monoceros some 5,000 light years away, the petals of this cosmic rose are actually a stellar nursery. The lovely, symmetric shape is sculpted by the winds and radiation from its central cluster of hot young, O-type stars. Stars in the energetic cluster, cataloged as NGC 2244, are only a few million years young, while the central cavity in the Rosette Nebula, is about 50 light-years in diameter. The nebula can be seen with a small telescope toward the constellation of Monoceros, the Unicorn. This natural appearing telescopic portrait of the Rosette Nebula was made using broadband and narrowband filters, because sometimes roses aren't red.

APOD: 2019 March 27 - NGC 1333: Stellar Nursery in Perseus
Explanation: NGC 1333 is seen in visible light as a reflection nebula, dominated by bluish hues characteristic of starlight reflected by interstellar dust. A mere 1,000 light-years distant toward the heroic constellation Perseus, it lies at the edge of a large, star-forming molecular cloud. This striking close-up spans about two full moons on the sky or just over 15 light-years at the estimated distance of NGC 1333. It shows details of the dusty region along with telltale hints of contrasty red emission from Herbig-Haro objects, jets and shocked glowing gas emanating from recently formed stars. In fact, NGC 1333 contains hundreds of stars less than a million years old, most still 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: 2019 January 3 - Ultima and Thule
Explanation: On January 1 New Horizons encountered the Kuiper Belt object nicknamed Ultima Thule. Some 6.5 billion kilometers from the Sun, Ultima Thule is the most distant world ever explored by a spacecraft from Earth. This historic image, the highest resolution image released so far, was made at a range of about 28,000 kilometers only 30 minutes before the New Horizons closest approach. Likely the result of a gentle collision shortly after the birth of the Solar System, Ultima Thule is revealed to be a contact binary, two connected sphere-like shapes held in contact by mutual gravity. Dubbed separately by the science team Ultima and Thule, the larger lobe Ultima is about 19 kilometers in diameter. Smaller Thule is 14 kilometers across.

APOD: 2018 November 14 - The Cave Nebula in Hydrogen, Oxygen, and Sulfur
Explanation: What's inside this cosmic cave? A stellar nursery 10 light-years deep. The featured skyscape is dominated by dusty Sh2-155, the Cave Nebula. In the telescopic image, data taken through a narrowband filters tracks the nebular glow of hydrogen, oxygen, and sulfur, colors that together form the Hubble Palette. About 2,400 light-years away, the scene lies along the plane of our Milky Way Galaxy toward the royal northern constellation of Cepheus. Astronomical explorations of the region reveal that it has formed at the boundary of the massive Cepheus B molecular cloud and the hot, young stars of the Cepheus OB 3 association. The bright rim of ionized hydrogen gas is energized by radiation from the hot stars, dominated by the bright star just to the left of the cave entrance. Radiation driven ionization fronts are likely triggering collapsing cores and new star formation within.

APOD: 2018 September 19 - Cocoon Nebula Deep Field
Explanation: Inside the Cocoon Nebula is a newly developing cluster of stars. The cosmic Cocoon on the upper right also punctuates a long trail of obscuring interstellar dust clouds to its left. Cataloged as IC 5146, the beautiful nebula is nearly 15 light-years wide, located some 3,300 light years away toward the northern constellation of the Swan (Cygnus). Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by young, hot stars and blue, dust-reflected starlight at the edge of a nearly invisible molecular cloud. In fact, the bright star near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it slowly clears out a cavity in the molecular cloud's star forming dust and gas. This exceptionally deep color view of the Cocoon Nebula traces tantalizing features within and surrounding the dusty stellar nursery.

APOD: 2018 March 21 - Camera Orion
Explanation: Do you recognize this constellation? Although it is one of the most recognizable star groupings on the sky, Orion's icons don't look quite as colorful to the eye as they do to a camera. In this 20-image digitally-composed mosaic, cool red giant Betelgeuse takes on a strong orange tint as the brightest star at the upper left. Orion's hot blue stars are numerous, with supergiant Rigel balancing Betelgeuse at the lower right, and Bellatrix at the upper right Lined up in Orion's belt are three stars all about 1,500 light-years away, born from the constellation's well-studied interstellar clouds. Below Orion's belt a reddish and fuzzy patch that might also look familiar -- the stellar nursery known as Orion's Nebula. Finally, just barely visible to the unaided eye but quite striking here by camera is Barnard's Loop -- a huge gaseous emission nebula surrounding Orion's Belt and Nebula discovered over 100 years ago by the pioneering Orion photographer E. E. Barnard.

APOD: 2018 February 18 - LL Ori and the Orion Nebula
Explanation: Stars can make waves in the Orion Nebula's sea of gas and dust. This esthetic close-up of cosmic clouds and stellar winds features LL Orionis, interacting with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged Sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The small, arcing, graceful structure just above and left of center is LL Ori's cosmic bow shock, measuring about half a light-year across. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the upper left corner of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. This beautiful painting-like photograph is part of a large mosaic view of the complex stellar nursery in Orion, filled with a myriad of fluid shapes associated with star formation.

APOD: 2018 January 17 - In the Valley of Orion
Explanation: This exciting and unfamiliar view of the Orion Nebula is a visualization based on astronomical data and movie rendering techniques. Up close and personal with a famous stellar nursery normally seen from 1,500 light-years away, the digitally modeled frame transitions from a visible light representation based on Hubble data on the left to infrared data from the Spitzer Space Telescope on the right. The perspective at the center looks along a valley over a light-year wide, in the wall of the region's giant molecular cloud. Orion's valley ends in a cavity carved by the energetic winds and radiation of the massive central stars of the Trapezium star cluster. The single frame is part of a multiwavelength, three-dimensional video that lets the viewer experience an immersive, three minute flight through the Great Nebula of Orion.

APOD: 2017 November 29 - M42: The Great Orion Nebula
Explanation: Few astronomical sights excite the imagination like the nearby stellar nursery known as the Orion Nebula. The Nebula's glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud. Many of the filamentary structures visible in the featured image are actually shock waves - fronts where fast moving material encounters slow moving gas. The Orion Nebula spans about 40 light years and is located about 1500 light years away in the same spiral arm of our Galaxy as the Sun. The Great Nebula in Orion can be found with the unaided eye just below and to the left of the easily identifiable belt of three stars in the popular constellation Orion. The featured image, taken last month, shows a two-hour exposure of the nebula in three colors. The whole Orion Nebula cloud complex, which includes the Horsehead Nebula, will slowly disperse over the next 100,000 years.

APOD: 2017 November 19 - NGC 7822: Stars and Dust Pillars in Infrared
Explanation: Young stars themselves are clearing out their nursery in NGC 7822. Within the nebula, bright edges and complex dust sculptures dominate this detailed skyscape taken in infrared light by NASA's Wide Field Infrared Survey Explorer (WISE) satellite. NGC 7822 lies at the edge of a giant molecular cloud toward the northern constellation Cepheus, a glowing star forming region that lies about 3,000 light-years away. The atomic emission of light by the nebula's gas is powered by energetic radiation from the hot stars, whose powerful winds and light also sculpt and erode the denser pillar shapes. Stars could still be forming inside the pillars by gravitational collapse, but as the pillars are eroded away, any forming stars will ultimately be cut off from their reservoir of star stuff. This field spans around 40 light-years at the estimated distance of NGC 7822.

APOD: 2017 March 23 - SH2-155: The Cave Nebula
Explanation: This skyscape features dusty Sharpless catalog emission region Sh2-155, the Cave Nebula. In the telescopic image, data taken through a narrowband filter tracks the reddish glow of ionized hydrogen atoms. About 2,400 light-years away, the scene lies along the plane of our Milky Way Galaxy toward the royal northern constellation of Cepheus. Astronomical explorations of the region reveal that it has formed at the boundary of the massive Cepheus B molecular cloud and the hot, young stars of the Cepheus OB 3 association. The bright rim of ionized hydrogen gas is energized by radiation from the hot stars, dominated by the brightest star above and left of picture center. Radiation driven ionization fronts are likely triggering collapsing cores and new star formation within. Appropriately sized for a stellar nursery, the cosmic cave is over 10 light-years across.

APOD: 2016 October 14 - Herschel's Orion
Explanation: This dramatic image peers within M42, the Orion Nebula, the closest large star-forming region. Using data at infrared wavelengths from the Herschel Space Observatory, the false-color composite explores the natal cosmic cloud a mere 1,500 light-years distant. Cold, dense filaments of dust that would otherwise be dark at visible wavelengths are shown in reddish hues. Light-years long, the filaments weave together bright spots that correspond to regions of collapsing protostars. The brightest bluish area near the top of the frame is warmer dust heated by the hot Trapezium cluster stars that also power the nebula's visible glow. Herschel data has recently indicated ultraviolet starlight from the hot newborn stars likely contributes to the creation of carbon-hydrogen molecules, basic building blocks of life. This Herschel image spans about 3 degrees on the sky. That's about 80 light-years at the distance of the Orion Nebula.

APOD: 2016 August 29 - Young Suns of NGC 7129
Explanation: Young suns still lie within dusty NGC 7129, some 3,000 light-years away toward the royal constellation Cepheus. While these stars are at a relatively tender age, only a few million years old, it is likely that our own Sun formed in a similar stellar nursery some five billion years ago. Most noticeable in the sharp image are the lovely bluish dust clouds that reflect the youthful starlight. But the compact, deep red crescent shapes are also markers of energetic, young stellar objects. Known as Herbig-Haro objects, their shape and color is characteristic of glowing hydrogen gas shocked by jets streaming away from newborn stars. Paler, extended filaments of reddish emission mingling with the bluish clouds are caused by dust grains effectively converting the invisible ultraviolet starlight to visible red light through photoluminesence. Ultimately the natal gas and dust in the region will be dispersed, the stars drifting apart as the loose cluster orbits the center of the Galaxy. The processing of this remarkable composite image has revealed the faint red strands of emission at the upper right. They are recently recognized as a likely supernova remnant and are currently being analyzed by Bo Reipurth (Univ. Hawaii) who obtained the image data at the Subaru telescope. At the estimated distance of NGC 7129, this telescopic view spans over 40 light-years.

APOD: 2016 July 28 - Herschel's Eagle Nebula
Explanation: A now famous picture from the Hubble Space Telescope featured Pillars of Creation, star forming columns of cold gas and dust light-years long inside M16, the Eagle Nebula. This false-color composite image views the nearby stellar nursery using data from the Herschel Space Observatory's panoramic exploration of interstellar clouds along the plane of our Milky Way galaxy. Herschel's far infrared detectors record the emission from the region's cold dust directly. The famous pillars are included near the center of the scene. While the central group of hot young stars is not apparent at these infrared wavelengths, the stars' radiation and winds carve the shapes within the interstellar clouds. Scattered white spots are denser knots of gas and dust, clumps of material collapsing to form new stars. The Eagle Nebula is some 6,500 light-years distant, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).

APOD: 2016 May 22 - LL Orionis: When Cosmic Winds Collide
Explanation: What created this great arc in space? This arcing, graceful structure is actually a bow shock about half a light-year across, created as the wind from young star LL Orionis collides with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the lower right hand edge of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. The complex stellar nursery in Orion shows a myriad of similar fluid shapes associated with star formation, including the bow shock surrounding a faint star at the upper right. Part of a mosaic covering the Great Nebula in Orion, this composite color image was recorded in 1995 by the Hubble Space Telescope.

APOD: 2016 April 24 - M16: Pillars of Star Creation
Explanation: Newborn stars are forming in the Eagle Nebula. This image, taken with the Hubble Space Telescope in 1995, shows 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 pillars' 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. The pillars of creation were imaged again in 2007 by the orbiting Spitzer Space Telescope in infrared light, leading to the conjecture that the pillars may already have been destroyed by a local supernova, but light from that event has yet to reach the Earth.

APOD: 2016 January 25 - Where Your Elements Came From
Explanation: The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe. The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen. Much of the iron in your body was made during supernovas of stars that occurred long ago and far away. The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts. Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life. The featured periodic table is color coded to indicate humanity's best guess as to the nuclear origin of all known elements. The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research.

APOD: 2016 January 13 - Reflections on the 1970s
Explanation: The 1970s are sometimes ignored by astronomers, like this beautiful grouping of reflection nebulae in Orion - NGC 1977, NGC 1975, and NGC 1973 - usually overlooked in favor of the substantial glow from the nearby stellar nursery better known as the Orion Nebula. Found along Orion's sword just north of the bright Orion Nebula complex, these reflection nebulae are also associated with Orion's giant molecular cloud about 1,500 light-years away, but are dominated by the characteristic blue color of interstellar dust reflecting light from hot young stars. In this sharp color image a portion of the Orion Nebula appears along the bottom border with the cluster of reflection nebulae at picture center. NGC 1977 stretches across the field just below center, separated from NGC 1973 (above right) and NGC 1975 (above left) by dark regions laced with faint red emission from hydrogen atoms. Taken together, the dark regions suggest to many the shape of a running man.

APOD: 2015 November 5 - NGC 1333: Stellar Nursery in Perseus
Explanation: NGC 1333 is seen in visible light as a reflection nebula, dominated by bluish hues characteristic of starlight reflected by interstellar dust. A mere 1,000 light-years distant toward the heroic constellation Perseus, it lies at the edge of a large, star-forming molecular cloud. This striking close-up spans about two full moons on the sky or just over 15 light-years at the estimated distance of NGC 1333. It shows details of the dusty region along with hints of contrasting red emission from Herbig-Haro objects, jets and shocked glowing gas emanating from recently formed stars. In fact, NGC 1333 contains hundreds of stars less than a million years old, most still 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: 2015 November 4 - The Great Orion Nebula M42
Explanation: The Great Nebula in Orion, also known as M42, is one of the most famous nebulae in the sky. The star forming region's glowing gas clouds and hot young stars are on the right in this sharp and colorful image that includes the bluish reflection nebulae NGC 1977 and friends on the left. Located at the edge of an otherwise invisible giant molecular cloud complex, these eye-catching nebulas represent only a small fraction of this galactic neighborhood's wealth of interstellar material. Within the well-studied stellar nursery, astronomers have also identified what appear to be numerous infant planetary systems. The gorgeous skyscape spans nearly two degrees or about 45 light-years at the Orion Nebula's estimated distance of 1,500 light-years.

APOD: 2015 October 15 - M16 and the Eagle Nebula
Explanation: A star cluster around 2 million years young surrounded by natal clouds of dust and glowing gas, M16 is also known as The Eagle Nebula. This beautifully detailed image of the region includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the ridge of bright emission left of center is another dusty starforming column known as the Fairy of Eagle Nebula. M16 and the Eagle Nebula lie about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).

APOD: 2015 September 7 - The Shark Nebula
Explanation: There is no sea on Earth large enough to contain the Shark nebula. This predator apparition poses us no danger, though, as it is composed only of interstellar gas and dust. Dark dust like that featured here is somewhat like cigarette smoke and created in the cool atmospheres of giant stars. After being expelled with gas and gravitationally recondensing, massive stars may carve intricate structures into their birth cloud using their high energy light and fast stellar winds as sculpting tools. The heat they generate evaporates the murky molecular cloud as well as causing ambient hydrogen gas to disperse and glow red. During disintegration, we humans can enjoy imagining these great clouds as common icons, like we do for water clouds on Earth. Including smaller dust nebulae such as Lynds Dark Nebula 1235 and Van den Bergh 149 & 150, the Shark nebula spans about 15 light years and lies about 650 light years away toward the constellation of the King of Aethiopia (Cepheus).

APOD: 2015 July 25 - Infrared Trifid
Explanation: The Trifid Nebula, also known as Messier 20, is easy to find with a small telescope, a well known stop in the nebula rich constellation Sagittarius. But where visible light pictures show the nebula divided into three parts by dark, obscuring dust lanes, this penetrating infrared image reveals filaments of glowing dust clouds and newborn stars. The spectacular false-color view is courtesy of the Spitzer Space Telescope. Astronomers have used the Spitzer infrared image data to count newborn and embryonic stars which otherwise can lie hidden in the natal dust and gas clouds of this intriguing stellar nursery. As seen here, the Trifid is about 30 light-years across and lies only 5,500 light-years away.

APOD: 2015 April 25 - Cluster and Starforming Region Westerlund 2
Explanation: Located 20,000 light-years away in the constellation Carina, the young cluster and starforming region Westerlund 2 fills this cosmic scene. Captured with Hubble's cameras in near-infrared and visible light, the stunning image is a celebration of the 25th anniversary of the launch of the Hubble Space Telescope on April 24, 1990. The cluster's dense concentration of luminous, massive stars is about 10 light-years across. Strong winds and radiation from those massive young stars have sculpted and shaped the region's gas and dust, into starforming pillars that point back to the central cluster. Red dots surrounding the bright stars are the cluster's faint newborn stars, still within their natal gas and dust cocoons. But brighter blue stars scattered around are likely not in the Westerlund 2 cluster and instead lie in the foreground of the Hubble anniversary field of view.

APOD: 2015 April 4 - Voorwerpjes in Space
Explanation: Mysterious Hanny's Voorwerp, Dutch for "Hanny's Object", is really enormous, about the size of the Milky Way Galaxy and glowing strongly in the greenish light produced by ionized oxygen atoms. It is thought to be a tidal tail of material left by an ancient galaxy merger, illuminated and ionized by the outburst of a quasar inhabiting the center of distant spiral galaxy IC 2497. Its exciting 2007 discovery by Dutch schoolteacher Hanny van Arkel while participating online in the Galaxy Zoo project has since inspired a search and discovery of eight more eerie green cosmic features. Imaged in these panels by the Hubble Space Telescope, all eight appear near galaxies with energetic cores. Far outside their associated galaxies, these objects are also likely echoes of quasar activity, illuminated only as light from a core quasar outburst reaches them and ultimately fading tens of thousands of years after the quasar outburst itself has faded away. Of course a galaxy merger like the impending merger of our own Milky Way and the Andromeda Galaxy, could also trigger the birth of a quasar that would illuminate our distant future version of Hanny's Voorwerp.

APOD: 2015 March 26 - Orion Spring
Explanation: As spring comes to planet Earth's northern hemisphere, familiar winter constellation Orion sets in early evening skies and budding trees frame the Hunter's stars. The yellowish hue of cool red supergiant Alpha Orionis, the great star Betelgeuse, mingles with the branches at the top of this colorful skyscape. Orion's alpha star is joined on the far right by Alpha Tauri. Also known as Aldebaran and also a giant star cooler than the Sun, it shines with a yellow light at the head of Taurus, the Bull. Contrasting blue supergiant Rigel, Beta Orionis, is Orion's other dominant star though, and marks the Hunter's foot below center. Of course, the sword of Orion hangs from the Hunter's three blue belt stars near picture center, but the middle star in the sword is not a star at all. A slightly fuzzy pinkish glow hints at its true nature, a nearby stellar nursery visible to the unaided eye known as the Orion Nebula.

APOD: 2015 February 25 - The Rosette Nebula in Hydrogen and Oxygen
Explanation: The Rosette Nebula is not the only cosmic cloud of gas and dust to evoke the imagery of flowers -- but it is the most famous. At the edge of a large molecular cloud in Monoceros, some 5,000 light years away, the petals of this rose are actually a stellar nursery whose lovely, symmetric shape is sculpted by the winds and radiation from its central cluster of hot young stars. The stars in the energetic cluster, cataloged as NGC 2244, are only a few million years old, while the central cavity in the Rosette Nebula, cataloged as NGC 2237, is about 50 light-years in diameter. The nebula can be seen firsthand with a small telescope toward the constellation of the Unicorn (Monoceros).

APOD: 2015 January 7 - Hubble 25th Anniversary: Pillars of Creation
Explanation: To celebrate 25 years (1990-2015) of exploring the Universe from low Earth orbit, the Hubble Space Telescope's cameras were used to revisit its most iconic image. The result is this sharper, wider view of the region dubbed the Pillars of Creation, first imaged by Hubble in 1995. Stars are forming deep inside the towering structures. The light-years long columns of cold gas and dust are some 6,500 light-years distant in M16, the Eagle Nebula, toward the constellation Serpens. Sculpted and eroded by the energetic ultraviolet light and powerful winds from M16's cluster of young, massive stars, the cosmic pillars themselves are destined for destruction. But the turbulent environment of star formation within M16, whose spectacular details are captured in this Hubble visible-light snapshot, is likely similar to the environment that formed our own Sun.

APOD: 2014 December 19 - Reflections on the 1970s
Explanation: The 1970s are sometimes ignored by astronomers, like this beautiful grouping of reflection nebulae in Orion - NGC 1977, NGC 1975, and NGC 1973 - usually overlooked in favor of the substantial glow from the nearby stellar nursery better known as the Orion Nebula. Found along Orion's sword just north of the bright Orion Nebula complex, these reflection nebulae are also associated with Orion's giant molecular cloud about 1,500 light-years away, but are dominated by the characteristic blue color of interstellar dust reflecting light from hot young stars. In this sharp color image a portion of the Orion Nebula appears along the bottom border with the cluster of reflection nebulae at picture center. NGC 1977 stretches across the field just below center, separated from NGC 1973 (above right) and NGC 1975 (above left) by dark regions laced with faint red emission from hydrogen atoms. Taken together, the dark regions suggest to many the shape of a running man.

APOD: 2014 November 11 - Orion in Gas, Dust, and Stars
Explanation: The constellation of Orion holds much more than three stars in a row. A deep exposure shows everything from dark nebulae to star clusters, all embedded in an extended patch of gaseous wisps in the greater Orion Molecular Cloud Complex. The brightest three stars on the far left are indeed the famous three stars that make up the belt of Orion. Just below Alnitak, the lowest of the three belt stars, is the Flame Nebula, glowing with excited hydrogen gas and immersed in filaments of dark brown dust. Below and left of the frame center and just to the right of Alnitak lies the Horsehead Nebula, a dark indentation of dense dust that has perhaps the most recognized nebular shapes on the sky. On the upper right lies M42, the Orion Nebula, an energetic caldron of tumultuous gas, visible to the unaided eye, that is giving birth to a new open cluster of stars. Immediately to the left of M42 is a prominent bluish reflection nebula sometimes called the Running Man that houses many bright blue stars. The featured image covers an area with objects that are roughly 1,500 light years away and spans about 75 light years.

APOD: 2014 November 6 - SH2-155: The Cave Nebula
Explanation: This colorful skyscape features the dusty Sharpless catalog emission region Sh2-155, the Cave Nebula. In the composite image, data taken through narrowband filters tracks the glow of ionized sulfur, hydrogen, and oxygen atoms in red, green, and blue hues. About 2,400 light-years away, the scene lies along the plane of our Milky Way Galaxy toward the royal northern constellation of Cepheus. Astronomical explorations of the region reveal that it has formed at the boundary of the massive Cepheus B molecular cloud and the hot, young stars of the Cepheus OB 3 association. The bright rim of ionized interstellar gas is energized by radiation from the hot stars, dominated by the bright star just above picture center. Radiation driven ionization fronts are likely triggering collapsing cores and new star formation within. Appropriately sized for a stellar nursery, the cosmic cave is over 10 light-years across.

APOD: 2014 June 30 - Peculiar Elliptical Galaxy Centaurus A
Explanation: What's happened to the center of this galaxy? Unusual and dramatic dust lanes run across the center of elliptical galaxy Centaurus A. These dust lanes are so thick they almost completely obscure the galaxy's center in visible light. This is particularly unusual as Cen A's red stars and round shape are characteristic of a giant elliptical galaxy, a galaxy type usually low in dark dust. Cen A, also known as NGC 5128, is also unusual compared to an average elliptical galaxy because it contains a higher proportion of young blue stars and is a very strong source of radio emission. Evidence indicates that Cen A is likely the result of the collision of two normal galaxies. During the collision, many young stars were formed, but details of the creation of Cen A's unusual dust belts are still being researched. Cen A lies only 13 million light years away, making it the closest active galaxy. Cen A, pictured above, spans 60,000 light years and can be seen with binoculars toward the constellation of Centaurus.

APOD: 2014 June 7 - M16 and the Eagle Nebula
Explanation: A star cluster around 2 million years young, M16 is surrounded by natal clouds of dust and glowing gas also known as The Eagle Nebula. This beautifully detailed image of the region includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the left edge of the frame is another dusty starforming column known as the Fairy of Eagle Nebula. M16 and the Eagle Nebula lie about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).

APOD: 2014 May 10 - Inside the Flame Nebula
Explanation: The Flame Nebula stands out in this optical image of the dusty, crowded star forming regions toward Orion's belt, a mere 1,400 light-years away. X-ray data from the Chandra Observatory and infrared images from the Spitzer Space Telescope can take you inside the glowing gas and obscuring dust clouds though. Swiping your cursor (or clicking the image) will reveal many stars of the recently formed, embedded cluster NGC 2024, ranging in age from 200,000 years to 1.5 million years young. The X-ray/infrared composite image overlay spans about 15 light-years across the Flame's center. The X-ray/infrared data also indicate that the youngest stars are concentrated near the middle of the Flame Nebula cluster. That's the opposite of the simplest models of star formation for the stellar nursery that predict star formation begins in the denser center of a molecular cloud core. The result requires a more complex model; perhaps star formation continues longer in the center, or older stars are ejected from the center due to subcluster mergers.

APOD: 2014 March 16 - The Antennae Galaxies in Collision
Explanation: Two galaxies are squaring off in Corvus and here are the latest pictures. When two galaxies collide, the stars that compose them usually do not. That's because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space. During the slow, hundred million year collision, one galaxy can still rip the other apart gravitationally, and dust and gas common to both galaxies does collide. In this clash of the titans, dark dust pillars mark massive molecular clouds are being compressed during the galactic encounter, causing the rapid birth of millions of stars, some of which are gravitationally bound together in massive star clusters.

APOD: 2014 January 15 - Spitzer's Orion
Explanation: Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This stunning false-color view spans about 40 light-years across the region, constructed using infrared data from the Spitzer Space Telescope. Compared to its visual wavelength appearance, the brightest portion of the nebula is likewise centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But the infrared image also detects the nebula's many protostars, still in the process of formation, seen here in red hues. In fact, red spots along the dark dusty filament to the left of the bright cluster include the protostar cataloged as HOPS 68, recently found to have crystals of the silicate mineral olivine within its protostellar envelope.

APOD: 2013 October 19 - Sh2-155: The Cave Nebula
Explanation: This colorful skyscape features the dusty, reddish glow of Sharpless catalog emission region Sh2-155, the Cave Nebula. About 2,400 light-years away, the scene lies along the plane of our Milky Way Galaxy toward the royal northern constellation of Cepheus. Astronomical explorations of the region reveal that it has formed at the boundary of the massive Cepheus B molecular cloud and the hot, young, blue stars of the Cepheus OB 3 association. The bright rim of ionized hydrogen gas is energized by the radiation from the hot stars, dominated by the bright blue O-type star above picture center. Radiation driven ionization fronts are likely triggering collapsing cores and new star formation within. Appropriately sized for a stellar nursery, the cosmic cave is over 10 light-years across.

APOD: 2013 September 29 - The Fairy of Eagle Nebula
Explanation: The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains, the statuesque pillars that remain might be imagined as mythical beasts. Pictured above is one of several striking dust pillars of the Eagle Nebula that might be described as a gigantic alien fairy. This fairy, however, is ten light years tall and spews radiation much hotter than common fire. The greater Eagle Nebula, M16, is actually a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars. The above image in scientifically re-assigned colors was released in 2005 as part of the fifteenth anniversary celebration of the launch of the Hubble Space Telescope.

APOD: 2013 August 17 - M8: The Lagoon Nebula
Explanation: This beautiful cosmic cloud is a popular stop on telescopic tours of the constellation Sagittarius. Eighteenth century cosmic tourist Charles Messier cataloged the bright nebula as M8. Modern day astronomers recognize the Lagoon Nebula as an active stellar nursery about 5,000 light-years distant, in the direction of the center of our Milky Way Galaxy. Hot stars in the embedded open star cluster NGC 6530 power the nebular glow. Remarkable features can be traced through this sharp picture, showing off the Lagoon's filaments of glowing gas and dark dust clouds. Twisting near the center of the Lagoon, the small, bright hourglass shape is the turbulent result of extreme stellar winds and intense starlight. The alluring color view was captured with a telescope and digital camera while M8 was high in dark, rural Argentina skies. At the nebula's estimated distance, the picture spans over 60 light-years.

APOD: 2013 July 14 - The Pillars of Eagle Castle
Explanation: What lights up this castle of star formation? The familiar Eagle Nebula glows bright in many colors at once. The above image is a composite of three of these glowing gas colors. Pillars of dark dust nicely outline some of the denser towers of star formation. Energetic light from young massive stars causes the gas to glow and effectively boils away part of the dust and gas from its birth pillar. Many of these stars will explode after several million years, returning most of their elements back to the nebula which formed them. This process is forming an open cluster of stars known as M16.

APOD: 2013 June 4 - Orion Nebula in Oxygen, Hydrogen, and Sulfur
Explanation: Few astronomical sights excite the imagination like the nearby stellar nursery known as the Orion Nebula. The Nebula's glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud. Many of the filamentary structures visible in the above image are actually shock waves - fronts where fast moving material encounters slow moving gas. The Orion Nebula spans about 40 light years and is located about 1500 light years away in the same spiral arm of our Galaxy as the Sun. The Great Nebula in Orion can be found with the unaided eye just below and to the left of the easily identifiable belt of three stars in the popular constellation Orion. The above image shows the nebula in three colors specifically emitted by hydrogen, oxygen, and sulfur gas. The whole Orion Nebula cloud complex, which includes the Horsehead Nebula, will slowly disperse over the next 100,000 years.

APOD: 2013 March 24 - Dust Pillar of the Carina Nebula
Explanation: Inside the head of this interstellar monster is a star that is slowly destroying it. The monster, actually an inanimate pillar of gas and dust, measures over a light year in length. The star, not itself visible through the opaque dust, is bursting out partly by ejecting energetic beams of particles. Similar epic battles are being waged all over the star-forming Carina Nebula (NGC 3372). The stars will win in the end, destroying their pillars of creation over the next 100,000 years, and resulting in a new open cluster of stars. The pink dots are newly formed stars that have already been freed from their birth monster. The above image is only a small part of a highly detailed panoramic mosaic of the Carina Nebula taken by the Hubble Space Telescope in 2007. The technical name for the stellar jets are Herbig-Haro objects. How a star creates Herbig-Haro jets is an ongoing topic of research, but it likely involves an accretion disk swirling around a central star. A second impressive Herbig-Haro jet is visible across the bottom of a larger image.

APOD: 2013 February 3 - LL Ori and the Orion Nebula
Explanation: This esthetic close-up of cosmic clouds and stellar winds features LL Orionis, interacting with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged Sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The small, arcing, graceful structure just above and left of center is LL Ori's cosmic bow shock, measuring about half a light-year across. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the upper left corner of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. The beautiful picture is part of a large mosaic view of the complex stellar nursery in Orion, filled with a myriad of fluid shapes associated with star formation.

APOD: 2013 January 19 - Barnard Stares at NGC 2170
Explanation: A gaze across a cosmic skyscape, this telescopic mosaic reveals the continuous beauty of things that are. The evocative scene spans some 6 degrees or 12 Full Moons in planet Earth's sky. At the left, folds of red, glowing gas are a small part of an immense, 300 light-year wide arc. Known as Barnard's loop, the structure is too faint to be seen with the eye, shaped by long gone supernova explosions and the winds from massive stars, and still traced by the light of hydrogen atoms. Barnard's loop lies about 1,500 light-years away roughly centered on the Great Orion Nebula, a stellar nursery along the edge of Orion's molecular clouds. But beyond lie other fertile star fields in the plane of our Milky Way Galaxy. At the right, the long-exposure composite finds NGC 2170, a dusty complex of nebulae near a neighboring molecular cloud some 2,400 light-years distant.

APOD: 2012 December 11 - NGC 604: Giant Stellar Nursery
Explanation: Stars are sometimes born in the midst of chaos. About 3 million years ago in the nearby galaxy M33, a large cloud of gas spawned dense internal knots which gravitationally collapsed to form stars. NGC 604 was so large, however, it could form enough stars to make a globular cluster. Many young stars from this cloud are visible in the above image from the Hubble Space Telescope, along with what is left of the initial gas cloud. Some stars were so massive they have already evolved and exploded in a supernova. The brightest stars that are left emit light so energetic that they create one of the largest clouds of ionized hydrogen gas known, comparable to the Tarantula Nebula in our Milky Way's close neighbor, the Large Magellanic Cloud.

APOD: 2012 July 22 - M16: Pillars of Creation
Explanation: It was one of the most famous images of the 1990s. This image, taken with the Hubble Space Telescope in 1995, shows 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 pillars' 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. The pillars of creation were imaged again in 2007 by the orbiting Spitzer Space Telescope in infrared light, leading to the conjecture that the pillars may already have been destroyed by a local supernova, but light from that event has yet to reach the Earth.

APOD: 2012 June 29 - Dark Clouds in Aquila
Explanation: Part of a dark expanse that splits the crowded plane of our Milky Way galaxy, the Aquila Rift arcs through the northern hemisphere's summer skies near bright star Altair and the Summer Triangle. In silhouette against the Milky Way's faint starlight, its dusty molecular clouds likely contain raw material to form hundreds of thousands of stars and astronomers eagerly search the clouds for telltale signs of star birth. This telescopic close-up looks toward the region at a fragmented Aquila dark cloud complex identified as LDN 673, stretching across a field of view slightly wider than the full moon. In the scene, visible indications of energetic outflows associated with young stars include the small red tinted nebulosity RNO 109 at top left and Herbig-Haro object HH32 above and right of center. The dark clouds in Aquila are estimated to be some 600 light-years away. At that distance, this field of view spans about 7 light-years.

APOD: 2012 May 17 - Herschel's Cygnus X
Explanation: The Herschel Space Observatory's infrared view of Cygnus X spans some 6x2 degrees across one of the closest, massive star forming regions in the plane of our Milky Way galaxy. In fact, the rich stellar nursery already holds the massive star cluster known as the Cygnus OB2 association. But those stars are more evident by the region cleared by their energetic winds and radiation near the bottom center of this field, and are not detected by Herschel instruments operating at long infrared wavelengths. Herschel does reveal the region's complex filaments of cool gas and dust that lead to dense locations where new massive stars are forming. Cygnus X lies some 4500 light-years away toward the heart of the northern constellation of the Swan. At that distance this picture would be almost 500 light-years wide.

APOD: 2012 May 6 - In the Center of the Omega Nebula
Explanation: In the depths of the dark clouds of dust and molecular gas known as the Omega Nebula, stars continue to form. The above image from the Hubble Space Telescope's Advanced Camera for Surveys shows exquisite detail in the famous star-forming region. The dark dust filaments that lace the center of Omega Nebula were created in the atmospheres of cool giant stars and in the debris from supernova explosions. The red and blue hues arise from glowing gas heated by the radiation of massive nearby stars. The points of light are the young stars themselves, some brighter than 100 Suns. Dark globules mark even younger systems, clouds of gas and dust just now condensing to form stars and planets. The Omega Nebula lies about 5000 light years away toward the constellation of Sagittarius. The region shown spans about 3000 times the diameter of our Solar System.

APOD: 2012 February 14 - The Rosette Nebula
Explanation: The Rosette Nebula is not the only cosmic cloud of gas and dust to evoke the imagery of flowers -- but it is the most famous. At the edge of a large molecular cloud in Monoceros, some 5,000 light years away, the petals of this rose are actually a stellar nursery whose lovely, symmetric shape is sculpted by the winds and radiation from its central cluster of hot young stars. The stars in the energetic cluster, cataloged as NGC 2244, are only a few million years old, while the central cavity in the Rosette Nebula, cataloged as NGC 2237, is about 50 light-years in diameter. The nebula can be seen firsthand with a small telescope toward the constellation of the Unicorn (Monoceros).

APOD: 2012 February 12 - Orion in Gas, Dust, and Stars
Explanation: The constellation of Orion holds much more than three stars in a row. A deep exposure shows everything from dark nebula to star clusters, all embedded in an extended patch of gaseous wisps in the greater Orion Molecular Cloud Complex. The brightest three stars on the far left are indeed the famous three stars that make up the belt of Orion. Just below Alnitak, the lowest of the three belt stars, is the Flame Nebula, glowing with excited hydrogen gas and immersed in filaments of dark brown dust. Below the frame center and just to the right of Alnitak lies the Horsehead Nebula, a dark indentation of dense dust that has perhaps the most recognized nebular shapes on the sky. On the upper right lies M42, the Orion Nebula, an energetic caldron of tumultuous gas, visible to the unaided eye, that is giving birth to a new open cluster of stars. Immediately to the left of M42 is a prominent bluish reflection nebula sometimes called the Running Man that houses many bright blue stars. The above image, a digitally stitched composite taken over several nights, covers an area with objects that are roughly 1,500 light years away and spans about 75 light years.

APOD: 2012 February 3 - Inside the Eagle Nebula
Explanation: In 1995, a now famous picture from the Hubble Space Telescope featured Pillars of Creation, star forming columns of cold gas and dust light-years long inside M16, the Eagle Nebula. This remarkable false-color composite image revisits the nearby stellar nursery with image data from the orbiting Herschel Space Observatory and XMM-Newton telescopes. Herschel's far infrared detectors record the emission from the region's cold dust directly, including the famous pillars and other structures near the center of the scene. Toward the other extreme of the electromagnetic spectrum, XMM-Newton's X-ray vision reveals the massive, hot stars of the nebula's embedded star cluster. Hidden from Hubble's view at optical wavelengths, the massive stars have a profound effect, sculpting and transforming the natal gas and dust structures with their energetic winds and radiation. In fact, the massive stars are short lived and astronomers have found evidence in the image data pointing to the remnant of a supernova explosion with an apparent age of 6,000 years. If true, the expanding shock waves would have destroyed the visible structures, including the famous pillars. But because the Eagle Nebula is some 6,500 light-years distant, their destruction won't be witnessed for hundreds of years.

APOD: 2011 December 18 - Hints of Higgs from the Large Hadron Collider
Explanation: Why do objects have mass? To help find out, Europe's CERN has built the Large Hadron Collider (LHC), the most powerful particle accelerator yet created by humans. Since 2008, the LHC has smashed protons into each other with unprecedented impact speeds. The LHC is exploring the leading explanation that mass arises from ordinary particles slogging through an otherwise invisible but pervasive field of virtual Higgs particles. Were high energy colliding particles to create real Higgs bosons, the Higgs mechanism for mass creation would be bolstered. Last week, two LHC groups reported on preliminary indications that the Higgs boson might exist around 120 GeV in mass. Data from the LHC collisions are also being scanned for micro black holes, magnetic monopoles, and exploring the possibility that every type of fundamental particle we know about has a nearly invisible supersymmetric counterpart. You can help -- the LHC@Home project will allow anyone with a home computer to help LHC scientists search archived LHC data for these strange beasts. Pictured above, a person stands in front of the huge ATLAS detector, one of six detectors attached to the LHC.

APOD: 2011 October 27 - Young Suns of NGC 7129
Explanation: Young suns still lie within dusty NGC 7129, some 3,000 light-years away toward the royal constellation Cepheus. While these stars are at a relatively tender age, only a few million years old, it is likely that our own Sun formed in a similar stellar nursery some five billion years ago. Most noticeable in the sharp image are the lovely bluish dust clouds that reflect the youthful starlight. But the compact, deep red crescent shapes are also markers of energetic, young stellar objects. Known as Herbig-Haro objects, their shape and color is characteristic of glowing hydrogen gas shocked by jets streaming away from newborn stars. Paler, extended filaments of reddish emission mingling with the bluish clouds are caused by dust grains effectively converting the invisible ultraviolet starlight to visible red light through photoluminesence. Ultimately the natal gas and dust in the region will be dispersed, the stars drifting apart as the loose cluster orbits the center of the Galaxy. At the estimated distance of NGC 7129, this telescopic view spans about 40 light-years.

APOD: 2011 September 17 - Spitzer's Orion
Explanation: Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This stunning false-color view spans about 40 light-years across the region, constructed using infrared data from the Spitzer Space Telescope. Compared to its visual wavelength appearance, the brightest portion of the nebula is likewise centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But the infrared image also detects the nebula's many protostars, still in the process of formation, seen here in red hues. In fact, red spots along the dark dusty filament to the left of the bright cluster include the protostar cataloged as HOPS 68, recently found to have crystals of the silicate mineral olivine within its protostellar envelope.

APOD: 2011 September 13 - Great Orion Nebulae
Explanation: The Great Nebula in Orion, also known as M42, is one of the most famous nebulas in the sky. The star forming region's glowing gas clouds and hot young stars are on the right in this sharp and colorful image that includes the smaller nebula M43 near center and dusty, bluish reflection nebulae NGC 1977 and friends on the left. Located at the edge of an otherwise invisible giant molecular cloud complex, these eye-catching nebulae represent only a small fraction of this galactic neighborhood's wealth of interstellar material. Within the well-studied stellar nursery, astronomers have also identified what appear to be numerous infant planetary systems. The gorgeous skyscape spans nearly two degrees or about 45 light-years at the Orion Nebula's estimated distance of 1,500 light-years.

APOD: 2011 August 21 - The Fairy of Eagle Nebula
Explanation: The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains, the statuesque pillars that remain might be imagined as mythical beasts. Pictured above is one of several striking dust pillars of the Eagle Nebula that might be described as a gigantic alien fairy. This fairy, however, is ten light years tall and spews radiation much hotter than common fire. The greater Eagle Nebula, M16, is actually a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars. The above image in scientifically re-assigned colors was released in 2005 as part of the fifteenth anniversary celebration of the launch of the Hubble Space Telescope.

APOD: 2011 June 11 - Supernovae in the Whirlpool
Explanation: Where do spiral galaxies keep their supernovae? Near their massive star forming regions, of course, and those regions tend to lie along sweeping blue spiral arms. Because massive stars are very short-lived, they don't have a chance to wander far from their birth place. Remarkably, in the last 6 years two Type II supernovae, representing the death explosions of massive stars, have been detected in nearby spiral M51. Along with a third supernova seen in 1994, that amounts to a supernova bonanza for a single galaxy. As demonstrated in these comparison images, SN2005cs, the supernova discovered in 2005, and more recently SN2011dh, the exceptionally bright supernova first recorded just last month, both lie along M51's grand spiral arms. Perhaps the original spiral nebula, M51 is also known as the Whirlpool Galaxy.

APOD: 2011 June 9 - The Great Carina Nebula
Explanation: A jewel of the southern sky, the Great Carina Nebula, also known as NGC 3372, spans over 300 light-years, one of our galaxy's largest star forming regions. Like the smaller, more northerly Great Orion Nebula, the Carina Nebula is easily visible to the unaided eye, though at a distance of 7,500 light-years it is some 5 times farther away. This gorgeous telescopic portrait reveals remarkable details of the region's glowing filaments of interstellar gas and obscuring cosmic dust clouds. Wider than the Full Moon in angular size, the field of view stretches nearly 100 light-years across the nebula. The Carina Nebula is home to young, extremely massive stars, including the still enigmatic variable Eta Carinae, a star with well over 100 times the mass of the Sun. Eta Carinae is the brightest star at the left, near the dusty Keyhole Nebula (NGC 3324). While Eta Carinae itself maybe on the verge of a supernova explosion, X-ray images indicate that the Great Carina Nebula has been a veritable supernova factory.

APOD: 2011 February 9 - NGC 2174: Stars Versus Mountains
Explanation: It's stars versus gas mountains in NGC 2174 and the stars are winning. More precisely, the energetic light and winds from massive newly formed stars are evaporating and dispersing the dark stellar nurseries in which they formed. The structures of NGC 2174 are actually much thinner than air and only appear as mountains due to relatively small amounts of opaque interstellar dust. A lesser known sight in the nebula-rich constellation Orion, NGC 2174 can be found with binoculars near the head of the celestial hunter. About 6,400 light-years distant, the entire glowing cosmic cloud covers an area larger than the full Moon and surrounds loose open clusters of young stars. The above image from the Hubble Space Telescope shows a dense interior region which spans only about three light years while adopting a color map that portrays otherwise red hydrogen emission in green hues and emphasizes sulfur emission in red and oxygen in blue. Within a few million years, the stars will likely win out completely and the entire dust mountain will be dispersed.

APOD: 2011 January 11 - The Cosmic Web of the Tarantula Nebula
Explanation: It is the largest and most complex star forming region in the entire galactic neighborhood. Located in the Large Magellanic Cloud, a small satellite galaxy orbiting our Milky Way galaxy, the region's spidery appearance is responsible for its popular name, the Tarantula nebula. This tarantula, however, is about 1,000 light-years across. Were it placed at the distance of Milky Way's Orion Nebula, only 1,500 light-years distant and the nearest stellar nursery to Earth, it would appear to cover about 30 degrees (60 full moons) on the sky. Intriguing details of the nebula are visible in the above image shown in scientific colors. The spindly arms of the Tarantula nebula surround NGC 2070, a star cluster that contains some of the brightest, most massive stars known, visible in blue on the right. Since massive stars live fast and die young, it is not so surprising that the cosmic Tarantula also lies near the site of the closest recent supernova.

APOD: 2010 November 2 - Spicules: Jets on the Sun
Explanation: Imagine a pipe as wide as a state and as long as the Earth. Now imagine that this pipe is filled with hot gas moving 50,000 kilometers per hour. Further imagine that this pipe is not made of metal but a transparent magnetic field. You are envisioning just one of thousands of young spicules on the active Sun. Pictured above is one of the highest resolution image yet of these enigmatic solar flux tubes. Spicules line the above frame of solar active region 11092 that crossed the Sun last month, but are particularly evident converging on the sunspot on the lower left. Time-sequenced images have recently shown that spicules last about five minutes, starting out as tall tubes of rapidly rising gas but eventually fading as the gas peaks and falls back down to the Sun. What determines the creation and dynamics of spicules remains a topic of active research.

APOD: 2010 October 23 - Orion: Head to Toe
Explanation: Cradled in cosmic dust and glowing hydrogen, stellar nurseries in Orion the Hunter lie at the edge of a giant molecular cloud some 1,500 light-years away. Spanning nearly 25 degrees, this breath-taking vista stretches across the well-known constellation from head to toe (left to right). The Great Orion Nebula, the closest large star forming region, is right of center. To its left are the Horsehead Nebula, M78, and Orion's belt stars. Sliding your cursor over the picture will also find red giant Betelgeuse at the hunter's shoulder, bright blue Rigel at his foot, and the glowing Lambda Orionis (Meissa) nebula at the far left, near Orion's head. Of course, the Orion Nebula and bright stars are easy to see with the unaided eye, but dust clouds and emission from the extensive interstellar gas in this nebula-rich complex, are too faint and much harder to record. In this mosaic of broadband telescopic images, additional image data acquired with a narrow hydrogen alpha filter was used to bring out the pervasive tendrils of energized atomic hydrogen gas and the arc of the giant Barnard's Loop.

APOD: 2010 August 5 - M8: The Lagoon Nebula
Explanation: This beautiful cosmic cloud is a popular stop on telescopic tours of the constellation Sagittarius. Eighteenth century cosmic tourist Charles Messier cataloged the bright nebula as M8. Modern day astronomers recognize the Lagoon Nebula as an active stellar nursery about 5,000 light-years distant, in the direction of the center of our Milky Way Galaxy. Remarkable features can be traced through this sharp picture, showing off the Lagoon's filaments of glowing gas and dark dust clouds. Twisting near the center of the Lagoon, the bright hourglass shape is the turbulent result of extreme stellar winds and intense starlight. The alluring view is a color composite of both broad and narrow band images captured while M8 was high in dark, Chilean skies. It records the Lagoon with a bluer hue than typically represented in images dominated by the red light of the region's hydrogen emission. At the nebula's estimated distance, the picture spans about 30 light-years.

APOD: 2010 July 18 - The Antennae Galaxies in Collision
Explanation: Two galaxies are squaring off in Corvus and here are the latest pictures. But when two galaxies collide, the stars that compose them usually do not. That's because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space. During the slow, hundred million year collision, one galaxy can still rip the other apart gravitationally, and dust and gas common to both galaxies does collide. In this clash of the titans, dark dust pillars mark massive molecular clouds are being compressed during the galactic encounter, causing the rapid birth of millions of stars, some of which are gravitationally bound together in massive star clusters.

APOD: 2010 June 26 - Young Star Cluster Westerlund 2
Explanation: Dusty stellar nursery RCW 49 surrounds young star cluster Westerlund 2 in this remarkable composite skyscape from beyond the visible spectrum of light. Infrared data from the Spitzer Space Telescope is shown in black and white, complementing the Chandra X-ray image data (in false color) of the hot energetic stars within the cluster's central region. Looking toward the grand southern constellation Centaurus, both views reveal stars and structures hidden from optical telescopes by obscuring dust. Westerlund 2 itself is a mere 2 million years old or less, and contains some of our galaxy's most luminous, massive and therefore short-lived stars. The infrared signatures of proto-planetary disks have also been identified in the intense star forming region. At the cluster's estimated distance of 20,000 light-years, the square marking the Chandra field of view would be about 50 light-years on a side.

APOD: 2010 May 1 - A Pulsar s Hand
Explanation: As far as pulsars go, PSR B1509-58 appears young. Light from the supernova explosion that gave birth to it would have first reached Earth some 1,700 years ago. The magnetized, 20 kilometer-diameter neutron star spins 7 times per second, a cosmic dynamo that powers a wind of charged particles. The energetic wind creates the surrounding nebula's X-ray glow in this tantalizing image from the Chandra X-ray Observatory. Low energy X-rays are in red, medium energies in green, and high energies in blue. The pulsar itself is in the bright central region. Remarkably, the nebula's tantalizing, complicated structure resembles a hand. PSR B1509-58 is about 17,000 light-years away in the southern constellation Circinus. At that distance the Chandra image spans 100 light-years.

APOD: 2010 April 26 - Dust Pillar of the Carina Nebula
Explanation: Inside the head of this interstellar monster is a star that is slowly destroying it. The monster, on the right, is actually an inanimate pillar of gas and dust that measures over a light year in length. The star, not itself visible through the opaque dust, is bursting out partly by ejecting energetic beams of particles. Similar epic battles are being waged all over the star-forming Carina Nebula. The stars will win in the end, destroying their pillars of creation over the next 100,000 years, and resulting in a new open cluster of stars. The pink dots around the image are newly formed stars that have already been freed from their birth monster. The above image was released last week in commemoration of the Hubble Space Telescopes 20th year of operation. The technical name for the stellar jets are Herbig-Haro objects. How a star creates Herbig-Haro jets is an ongoing topic of research, but it likely involves an accretion disk swirling around a central star. A second impressive Herbig-Haro jet occurs diagonally near the image center.

APOD: 2010 March 28 - M16: Pillars of Creation
Explanation: It has become one of the most famous images of modern times. This image, taken with the Hubble Space Telescope in 1995, shows 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 pillars' 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. The pillars of creation were again imaged by the orbiting Chandra X-ray Observatory, and it was found that most EGGS are not strong emitters of X-rays.

APOD: 2009 December 8 - Ice Moon Tethys from Saturn Orbiting Cassini
Explanation: What processes formed the unusual surface of Saturn's moon Tethys? To help find out, NASA sent the robotic Cassini spacecraft right past the enigmatic ice moon in 2005. Pictured above is one of the highest resolution images of an entire face of Tethys yet created. The pervasive white color of Tethys is thought to be created by fresh ice particles continually falling onto the moon from Saturn's diffuse E-ring -- particles expelled by Saturn's moon Enceladus. Some of the unusual cratering patterns on Tethys remain less well understood, however. Close inspection of the above image of Tethys' south pole will reveal a great rift running diagonally down from the middle: Ithaca Chasma. A leading theory for the creation of this great canyon is anchored in the tremendous moon-wide surface cracking that likely occurred when Tethys' internal oceans froze. If so, Tethys may once have harbored internal oceans, possibly similar to the underground oceans some hypothesize to exist under the surface of Enceladus today. Might ancient life be frozen down there?

APOD: 2009 October 20 - A Solar Prominence Erupts in STEREO
Explanation: What does a solar prominence look like in three dimensions? To help find out, NASA launched the STEREO satellites to keep a steady eye on the Sun from two different vantage points. The STEREO satellites orbit the Sun nearly along Earth's orbit, but one (dubbed Ahead) currently leads the Earth, while the other (dubbed Behind) currently trails. Three weeks ago, a powerful prominence erupted and remained above the Sun for about 30 hours, allowing the STEREO satellites to get numerous views of the prominence from different angles. Pictured above is a high-resolution image of the event from the STEREO Ahead satellite. A video of the prominence erupting as seen from both spacecraft can be found here. The unusually quiet nature of the Sun over the past two years has made large prominences like this relatively rare. The combined perspective of STEREO will help astronomers better understand the mechanisms for the creation and evolution of prominences, coronal mass ejections, and flares.

APOD: 2009 October 2 - Comet and Orion
Explanation: These colorful panels both feature a familiar astronomical sight: the stellar nursery known as the Great Orion Nebula. They also offer an intriguing and unfamiliar detail of the nebula rich skyscape -- a passing comet. Recorded this weekend with a remotely operated telescope in New Mexico, the right hand image was taken on September 26 and the left on September 27. Comet 217P Linear sports an extended greenish tail and lies above the bluish Running Man reflection nebula near the top of both frames. Nearby and moving rapidly through the night sky, the comet's position clearly shifts against the cosmic nebulae and background stars from one night to the next. In fact, the comet was a mere 5 light-minutes away on September 27, compared to 1,500 light-years for the Orion Nebula. Much too faint to be seen with the unaided eye, Comet 217P Linear is a small periodic comet with an orbital period of about 8 years. At its most distant point from the Sun, the comet's orbit is calculated to reach beyond the orbit of Jupiter At its closest point to the Sun, the comet still lies just beyond the orbit of planet Earth.

APOD: 2009 September 29 - Orion in Gas, Dust, and Stars
Explanation: The constellation of Orion holds much more than three stars in a row. A deep exposure shows everything from dark nebula to star clusters, all imbedded in an extended patch of gaseous wisps in the greater Orion Molecular Cloud Complex. The brightest three stars on the far left are indeed the famous three stars that make up the belt of Orion. Just below Alnitak, the lowest of the three belt stars, is the Flame Nebula, glowing with excited hydrogen gas and immersed in filaments of dark brown dust. Below the frame center and just to the right of Alnitak lies the Horsehead Nebula, a dark indentation of dense dust that has perhaps the most recognized nebular shapes on the sky. On the upper right lies M42, the Orion Nebula, an energetic caldron of tumultuous gas, visible to the unaided eye, that is giving birth to a new open cluster of stars. Immediately to the left of M42 is a prominent bluish reflection nebula sometimes called the Running Man that houses many bright blue stars. The above image, a digitally stitched composite taken over several nights, covers an area with objects that are roughly 1,500 light years away and spans about 75 light years.

APOD: 2009 August 2 - Stars, Dust and Nebula in NGC 6559
Explanation: When stars form, pandemonium reigns. A textbook case is the star forming region NGC 6559. Visible above are red glowing emission nebulas of hydrogen, blue reflection nebulas of dust, dark absorption nebulas of dust, and the stars that formed from them. The first massive stars formed from the dense gas will emit energetic light and winds that erode, fragment, and sculpt their birthplace. And then they explode. The resulting morass can be as beautiful as it is complex. After tens of millions of years, the dust boils away, the gas gets swept away, and all that is left is a naked open cluster of stars.

APOD: 2009 July 10 - The Pillars of Eagle Castle
Explanation: What lights up this castle of star formation? The familiar Eagle Nebula glows bright in many colors at once. The above image is a composite of three of these glowing gas colors. Pillars of dark dust nicely outline some of the denser towers of star formation. Energetic light from young massive stars causes the gas to glow and effectively boils away part of the dust and gas from its birth pillar. Many of these stars will explode after several million years, returning most of their elements back to the nebula which formed them. This process is forming an open cluster of stars known as M16.

APOD: 2009 June 2 - Spoke's Reappear on Saturns Rings
Explanation: What causes the mysterious spokes in Saturn's rings? Visible in the above image as light ghostlike impressions, spokes were first discovered in the mid-1970s and first photographed by the Voyager spacecraft that buzzed by Saturn in the early 1980s. Their existence was unexpected. Oddly, the spokes are more commonly observed when Saturn's rings are more nearly edge on to the Sun, and so were conspicuously absent from initial images sent back by the robot Cassini spacecraft now orbiting Saturn. Analyses of archived Voyager images have led to the conclusions that the transient spokes, which may form and dissipate over a few hours, are composed of electrically charged sheets of small dust-sized particles. Hypotheses for spoke creation include small meteors impacting the rings and electron beams from Saturnian atmospheric lightning spraying the rings. As Saturn approaches equinox, spoke sightings like that pictured above are becoming increasingly common, giving planetary scientists fresh images and data with which to test origin hypotheses.

APOD: 2009 April 29 - GRB 090423: The Farthest Explosion Yet Measured
Explanation: An explosion so powerful it was seen clear across the visible universe was recorded in gamma-radiation last week by NASA's orbiting Swift Observatory. Farther than any known galaxy, quasar, or optical supernova, the gamma-ray burst recorded last week was clocked at redshift 8.2, making it the farthest explosion of any type yet detected. Occurring only 630 million years after the Big Bang, GRB 090423 detonated so early that astronomers had no direct evidence that anything explodable even existed back then. The faint infrared afterglow of GRB 090423 was recovered by large ground telescopes within minutes of being discovered. The afterglow is circled in the above picture taken by the large Gemini North Telescope in Hawaii, USA. An exciting possibility is that this gamma-ray burst occurred in one of the very first generation of stars and announced the birth of an early black hole. Surely, GRB 090423 provides unique data from a relatively unexplored epoch in our universe and a distant beacon from which the intervening universe can be studied.

APOD: 2009 April 21 - Global Warming Predictions
Explanation: How much will the Earth's surface warm up over the lives of our children? No one is sure. Compared to the past 100 million years, the Earth is currently enduring a relative cold spell, possibly about four degrees Celsius below average. Over the past 100 years, however, data indicate the average global temperature of the Earth has increased by nearly one degree Celsius. Few disagree that recent global warming is occurring, and the Intergovernmental Panel on Climate Change (IPCC) has concluded that we humans have created a warming surge that is likely to continue. A future temperature increase like that shown on the above predictive map may cause sea levels to rise, precipitation patterns to change, and much pole ice to melt. The result could impact many local agricultures and the global economy. Geoengineering projects that might include artificial cloud creation might reduce the amount of warming sunlight that reaches the Earth's surface.

APOD: 2009 March 5 - IC 5146: The Cocoon Nebula
Explanation: Inside the Cocoon Nebula is a newly developing cluster of stars. Cataloged as IC 5146, the beautiful nebula is nearly 15 light-years wide, located some 4,000 light years away toward the northern constellation Cygnus. Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by young, hot stars and blue, dust-reflected starlight at the edge of an otherwise invisible molecular cloud. In fact, the bright star near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it clears out a cavity in the molecular cloud's star forming dust and gas. This exceptionally deep color view of the Cocoon Nebula traces tantalizing features within and surrounding the dusty stellar nursery.

APOD: 2009 February 16 - The Great Carina Nebula
Explanation: A jewel of the southern sky, the Great Carina Nebula, aka NGC 3372, spans over 300 light-years, one of our Galaxy's largest star forming regions. Like the smaller, more northerly Great Orion Nebula, the Carina Nebula is easily visible to the unaided eye, though at a distance of 7,500 light-years it is some 5 times farther away. This stunning telescopic view from the 2.2-meter ESO/MPG telescope La Silla Observatory in Chile reveals remarkable details of the region's glowing filaments of interstellar gas and dark cosmic dust clouds. The Carina Nebula is home to young, extremely massive stars, including the still enigmatic variable Eta Carinae, a star with well over 100 times the mass of the Sun. Eta Carinae is the bright star left of the central dark notch in this field and near the dusty Keyhole Nebula (NGC 3324).

APOD: 2009 February 5 - NGC 604: X-rays from a Giant Stellar Nursery
Explanation: Some 3 million light-years distant in nearby spiral galaxy M33, giant stellar nursery NGC 604 is about 1,300 light-years across, or nearly 100 times the size of the Orion Nebula. In fact, among the star forming regions within the Local Group of galaxies, NGC 604 is second in size only to 30 Doradus, also known as the Tarantula Nebula in the Large Magellanic Cloud. This space-age color composite of X-ray data (in blue hues) from the Chandra Observatory, and Hubble optical data shows that NGC 604's cavernous bubbles and cavities are filled with a hot, tenuous, X-ray emitting gas. Intriguingly, NGC 604 itself is divided by a wall of relatively cool gas. On the western (right) side of the nebula, measurements indicate that material is likely heated to X-ray temperatures by the energetic winds from a cluster of about 200 young, massive stars. On the eastern side the X-ray filled cavities seem to be older, suggesting supernova explosions from the end of massive star evolution contribute to their formation.

APOD: 2008 November 11 - The Cosmic Web of the Tarantula Nebula
Explanation: First cataloged as a star, 30 Doradus is actually an immense star forming region in nearby galaxy The Large Magellanic Cloud. The region's spidery appearance is responsible for its popular name, the Tarantula nebula, except that this tarantula is about 1,000 light-years across, and 180,000 light-years away in the southern constellation Dorado. If the Tarantula nebula were at the distance of the Orion Nebula (1,500 light-years), the nearest stellar nursery to Earth, it would appear to cover about 30 degrees (60 full moons) on the sky. The spindly arms of the Tarantula nebula surround NGC 2070, a star cluster that contains some of the brightest, most massive stars known. Intriguing details of the nebula are visible in this scientifically-colored image. The cosmic Tarantula also lies near the site of the closest recent supernova.

APOD: 2008 October 23 - Great Orion Nebulae
Explanation: The Great Nebula in Orion, also known as M42, is one of the most famous nebulae in the sky. The star forming region's glowing gas clouds and hot young stars are on the right in this sharp and colorful two frame mosaic that includes the smaller nebula M43 near center and dusty, bluish reflection nebulae NGC 1977 and friends on the left. Located at the edge of an otherwise invisible giant molecular cloud complex, these eye-catching nebulae represent only a small fraction of this galactic neighborhood's wealth of interstellar material. Within the well-studied stellar nursery, astronomers have also identified what appear to be numerous infant solar systems. The gorgeous skyscape spans nearly two degrees or about 45 light-years at the Orion Nebula's estimated distance of 1,500 light-years.

APOD: 2008 October 3 - Young Suns of NGC 7129
Explanation: Young suns still lie within dusty NGC 7129, some 3,000 light-years away toward the royal constellation Cepheus. While these stars are at a relatively tender age, only about a million years old, it is likely that our own Sun formed in a similar stellar nursery some five billion years ago. Most noticeable in the striking image are the lovely bluish dust clouds that reflect the youthful starlight, but the smaller, deep red crescent shapes are also markers of energetic, young stellar objects. Known as Herbig-Haro objects, their shape and color is characteristic of glowing hydrogen gas shocked by jets streaming away from newborn stars. Ultimately the natal gas and dust in the region will be dispersed, the stars drifting apart as the loose cluster orbits the center of the Galaxy. At the estimated distance of NGC 7129, this telescopic view spans about 40 light-years.

APOD: 2008 September 16 - W5: Pillars of Star Creation
Explanation: How do stars form? A study of star forming region W5 by the sun-orbiting Spitzer Space Telescope provides clear clues by recording that massive stars near the center of empty cavities are older than stars near the edges. A likely reason for this is that the older stars in the center are actually triggering the formation of the younger edge stars. The triggered star formation occurs when hot outflowing gas compresses cooler gas into knots dense enough to gravitationally contract into stars. Spectacular pillars, left slowly evaporating from the hot outflowing gas, provide further visual clues. In the above scientifically-colored infrared image, red indicates heated dust, while white and green indicate particularly dense gas clouds. W5 is also known as IC 1848, and together with IC 1805 form a complex region of star formation popularly dubbed the Heart and Soul Nebulas. The above image highlights a part of W5 spanning about 2,000 light years that is rich in star forming pillars. W5 lies about 6,500 light years away toward the constellation of Cassiopeia.

APOD: 2008 August 29 - Generations of Stars in W5
Explanation: Giant star forming region W5 is over 200 light-years across and about 6,500 light-years away in the constellation Cassiopeia. W5's sculpted clouds of cold gas and dust seem to form fantastic shapes in this impressive mosaic of infrared images from the Spitzer Space Telescope. In fact, the area on the right includes the structures previously dubbed the Mountains of Creation. New evidence indicates that successive generations of stars formed in the W5 region in an expanding pattern of triggered star formation. The older, earlier generations of stars seem to cluster near the middle of the enormous cavities, with younger stars seen near the rims. Winds and radiation from the older, central stars likely carve out and compress surrounding interstellar material, triggering the collapse that gave rise to younger, later generations of stars farther out. In the false-color image, heated dust still within the cavities appears red, while the youngest stars are forming in the whitish areas. W5 is also known as IC 1848, and together with IC 1805 it is part of a complex region popularly dubbed the Heart and Soul Nebulae.

APOD: 2008 August 27 - IC 5146: The Cocoon Nebula
Explanation: Inside the Cocoon Nebula is a newly developing cluster of stars. Cataloged as IC 5146, the beautiful nebula is nearly 15 light-years wide, located some 4,000 light years away toward the northern constellation Cygnus. Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by young, hot stars and blue, dust-reflected starlight at the edge of an otherwise invisible molecular cloud. In fact, the bright star near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it clears out a cavity in the molecular cloud's star forming dust and gas. This color view of the Cocoon Nebula traces remarkably subtle features within and surrounding the dusty stellar nursery.

APOD: 2008 August 15 - 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 10 million light-years away, behind a veil of foreground dust and stars in the high and far-off constellation of Cepheus. 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 at least nine supernovae, the death explosions of massive stars, were discovered in NGC 6946. In this deep color composite image, a small barred structure is just visible at the galaxy's core. Nearly 40,000 light-years across, NGC 6946 is also known as the Fireworks Galaxy.

APOD: 2008 July 19 - M16 and the Eagle Nebula
Explanation: Young star cluster M16 is surrounded by natal clouds of cosmic dust and glowing gas also known as The Eagle Nebula. This beautifully detailed image of the region includes fantastic shapes made famous in well-known Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the upper left edge of the nebula is another dusty starforming column known as the Fairy of Eagle Nebula. M16 and the Eagle Nebula lie about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).

APOD: 2008 February 27 - The Eagle Nebula in Hydrogen, Oxygen, and Sulfur
Explanation: Bright blue stars are still forming in the dark pillars of the Eagle Nebula. Made famous by a picture from the Hubble Space Telescope in 1995, the Eagle Nebula shows the dramatic process of star formation. The above picture taken by a 0.8-meter telescope in the Canary Islands captures part of M16, the open cluster of stars that is being created. The high amount of detail in the above image results from it being taken only in specific colors of light emitted by hydrogen, oxygen, and sulfur. The bright blue stars of M16 have been continually forming over the past 5 million years, most recently in the famous central gas and dust columns that have been informally dubbed the Pillars of Creation and the Fairy. Light takes about 7,000 years to reach us from M16, which spans about 20 light years and can be seen with binoculars toward the constellation of the Serpent (Serpens).

APOD: 2008 February 14 - Long Stem Rosette
Explanation: The Rosette Nebula (aka NGC 2237) is not the only cosmic cloud of gas and dust to evoke the imagery of flowers. But it is the one most often suggested as a suitable astronomy image for Valentine's Day. Of the many excellent Rosette Nebula pictures submitted to APOD editors, this view seemed most appropriate, with a long stem of glowing hydrogen gas in the region included in the composition. At the edge of a large molecular cloud in Monoceros, some 5,000 light years away, the petals of this rose are actually a stellar nursery whose lovely, symmetric shape is sculpted by the winds and radiation from its central cluster of hot young stars. The stars in the energetic cluster, cataloged as NGC 2244, are only a few million years old, while the central cavity in the Rosette Nebula is about 50 light-years in diameter. Happy Valentine's Day!

APOD: 2008 January 31 - Young Star Cluster Westerlund 2
Explanation: Dusty stellar nursery RCW 49 surrounds young star cluster Westerlund 2 in this remarkable composite skyscape from beyond the visible spectrum of light. Infrared data from the Spitzer Space Telescope is shown in black and white, complimenting the Chandra X-ray image data (in false color) of the hot energetic stars within the cluster's central region. Looking toward the grand southern constellation Centaurus, both views reveal stars and structures hidden from optical telescopes by obscuring dust. Westerlund 2 itself is a mere 2 million years old or less, and contains some of our galaxy's most luminous, massive and therefore short-lived stars. The infrared signatures of proto-planetary disks have also been identified in the intense star forming region. At the cluster's estimated distance of 20,000 light-years, the square marking the Chandra field of view would be about 50 light-years on a side.

APOD: 2007 December 20 - Reflections on the 1970s
Explanation: The 1970s are sometimes ignored by astronomers. In particular, this beautiful grouping of reflection nebulae in Orion - NGC 1977, NGC 1975, and NGC 1973 - are usually overlooked in favor of the substantial glow from the nearby stellar nursery better known as the Orion Nebula. Found along Orion's sword just north of the bright Orion Nebula complex, these reflection nebulae are also associated with Orion's giant molecular cloud about 1,500 light-years away, but are dominated by the characteristic blue color of interstellar dust reflecting light from hot young stars. North is down in this sharp color telescopic image from New South Wales, Australia, so the more familiar Orion Nebula borders the top of the view. NGC 1977 stretches across the field just above center, separated from NGC 1973 (below left) and NGC 1975 (below right) by darker regions of obscuring dust. Many northern hemisphere observers claim to see the general shape of a running man in the cosmic dust cloud but, of course, they're looking at the view upside down.

APOD: 2007 December 15 - Mountains of Creation
Explanation: This fantastic skyscape lies at the eastern edge of giant stellar nursery W5, about 7,000 light-years away in the constellation Cassiopeia. An infrared view from the Spitzer Space Telescope, it features interstellar clouds of cold gas and dust sculpted by winds and radiation from a hot, massive star outside the picture (just above and to the right). Still swaddled within the cosmic clouds, newborn stars are revealed by Spitzer's penetrating gaze, their formation also triggered by the massive star. Fittingly dubbed "Mountains of Creation", these interstellar clouds are about 10 times the size of the analogous Pillars of Creation in M16, made famous in a 1995 Hubble Space Telescope view. W5 is also known as IC 1848 and together with IC 1805 it is part of a complex region popularly dubbed the Heart and Soul Nebulae. The Spitzer image spans about 70 light-years at the distance of W5.

APOD: 2007 October 6 - X-Ray Stars of Orion
Explanation: The stars of Orion shine brightly in visible light in planet Earth's night sky. The constellation harbors the closest large stellar nursery, the Great Nebula of Orion, a mere 1,500 light-years away. In fact, the apparently bright clump of stars near the center of this false color Chandra x-ray telescope picture are the massive stars of the Trapezium - the young star cluster which powers much of the nebula's visible-light glow. The stars shown in blue and orange are young sun-like stars; prodigious sources of x-rays thought to be produced in hot stellar coronae and surface flares in a young star's strong magnetic field. Our middle-aged Sun itself was probably thousands of times brighter in x-rays when, like the Trapezium stars, it was only a few million years old. The x-ray image spans about 2.5 light-years across the central region of the Orion Nebula.

APOD: 2007 July 7 - Infrared Trifid
Explanation: The Trifid Nebula, aka Messier 20, is easy to find with a small telescope, a well known stop in the nebula rich constellation Sagittarius. But where visible light pictures show the nebula divided into three parts by dark, obscuring dust lanes, this penetrating infrared image reveals filaments of glowing dust clouds and newborn stars. The spectacular false-color view is courtesy of the Spitzer Space Telescope. Astronomers have used the Spitzer infrared image data to count newborn and embryonic stars which otherwise can lie hidden in the natal dust and gas clouds of this intriguing stellar nursery. As seen here, the Trifid is about 30 light-years across and lies only 5,500 light-years away.

APOD: 2007 April 30 - Dust Pillar of the Carina Nebula
Explanation: Inside the head of this interstellar monster is a star that is slowly destroying it. The monster, actually an inanimate pillar of gas and dust, measures over a light year in length. The star, not itself visible through the opaque dust, is bursting out partly by ejecting energetic beams of particles. Similar epic battles are being waged all over the star-forming Carina Nebula. The stars will win in the end, destroying their pillars of creation over the next 100,000 years, and resulting in a new open cluster of stars. The pink dots are newly formed stars that have already been freed from their birth monster. The above image is only a small part of a highly detailed panoramic mosaic of the Carina Nebula taken by the Hubble Space Telescope and released last week. The technical name for the stellar jets are Herbig-Haro objects. How a star creates Herbig-Haro jets is an ongoing topic of research, but it likely involves an accretion disk swirling around a central star. A second impressive Herbig-Haro jet is visible across the bottom of a larger image.

APOD: 2007 February 18 - M16: Pillars of Creation
Explanation: It has become one of the most famous images of modern times. This image, taken with the Hubble Space Telescope in 1995, shows 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 pillars' 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. The pillars of creation were imaged recently by the orbiting Chandra X-ray Observatory, and it was found that most EGGS are not strong emitters of X-rays.

APOD: 2007 January 25 - Orion's Cradle
Explanation: Cradled in glowing hydrogen, stellar nurseries in Orion lie at the edge of a giant molecular cloud some 1,500 light-years away. This breath-taking view spans about 13 degrees across the center of the well-known constellation with the Great Orion Nebula, the closest large star forming region, just right of center. The deep mosaic also includes (left of center), the Horsehead Nebula, the Flame Nebula, and Orion's belt stars. Image data acquired with a hydrogen alpha filter adds other remarkable features to this wide angle cosmic vista -- pervasive tendrils of energized atomic hydrogen gas and portions of the surrounding Barnard's Loop. While the Orion Nebula and belt stars are easy to see with the unaided eye, emission from the extensive interstellar gas is faint and much harder to record, even in telescopic views of the nebula-rich complex.

APOD: 2006 October 24 - The Antennae Galaxies in Collision
Explanation: Two galaxies are squaring off in Corvus and here are the latest pictures. When two galaxies collide, however, the stars that compose them usually do not. This is because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space. During the slow, hundred million year collision, however, one galaxy can rip the other apart gravitationally, and dust and gas common to both galaxies does collide. In the above clash of the titans, dark dust pillars mark massive molecular clouds are being compressed during the galactic encounter, causing the rapid birth of millions of stars, some of which are gravitationally bound together in massive star clusters.

APOD: 2006 September 19 - Beagle Crater on Mars
Explanation: What have we found on the way to large Victoria Crater? Smaller Beagle Crater. The robotic Opportunity rover rolling across Mars stopped at Beagle Crater early last month and took an impressively detailed 360-degree panorama of the alien Martian landscape. Beagle crater appears in the center as a dip exposing relatively dark sand. Surrounding 35-meter Beagle Crater are many of the rocks ejected during its creation impact. Opportunity's detailed images show significant erosion on the rocks and walls of Beagle Crater, indicating that the crater is not fresh. Beagle Crater's unofficial name derives from the ship HMS Beagle where Charles Darwin observations led him to postulate his theory of natural selection. That ship was named after the dog breed of beagle. Opportunity is scheduled to roll up to expansive Victoria Crater this week.

APOD: 2006 August 18 - Spitzer's Orion
Explanation: Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. Also known as M42, the nebula is visible to the unaided eye, but this stunning infrared view from the Spitzer Space Telescope penetrates the turbulent cosmic gas and dust clouds to explore the region in unprecedented detail. At full resolution, the remarkable image data yields a census of new stars and potential solar systems. About 2,300 young stars surrounded by planet-forming disks were detected based on the infrared glow of their warm dust, along with about 200 stellar embryos, stars too young to have developed disks. This 0.8 by 1.4 degree false-color image is about 20 light-years wide at the distance of the Orion Nebula.

APOD: 2006 February 25 - SOFIA's Window Seat
Explanation: Earlier this month, a 2.5-meter diameter infrared telescope was permanently assigned a window seat, looking through this opening in the fuselage of a historic Boeing 747 aircraft. The telescope mirror, about the size of the Hubble Space Telescope mirror, is protected by a red covering. Known as the Stratospheric Observatory For Infrared Astronomy (SOFIA), the airborne observatory is intended to fly at altitudes up to 45,000 feet - above more than 99% of the atmospheric water vapor. Water vapor strongly absorbs infrared light, so at that altitude SOFIA will be able to acquire infrared images not possible for even the largest ground-based telescopes. SOFIA's unique capabilities will include the ability to trace complex molecules in the cosmic environments surrounding star birth and death and the formation of new solar systems. The SOFIA aircraft was operated by Pan American World Airways and was originally christened the "Clipper Lindbergh". The airborne observatory was designed with an on board console for teachers and other educators to participate in research flights.

APOD: 2006 February 10 - M8: The Lagoon Nebula
Explanation: This beautiful cosmic cloud is a popular stop on telescopic tours of the constellation Sagittarius. Eighteenth century cosmic tourist Charles Messier cataloged the bright nebula as M8, while modern day astronomers recognize the Lagoon Nebula as an active stellar nursery about 5,000 light-years distant, in the direction of the center of our Milky Way Galaxy. Striking details can be traced through this remarkable picture, processed to reveal the Lagoon's range of filaments of glowing hydrogen gas and dark dust clouds along with the brighter, turbulent hourglass region at the upper right. The view is a color composite of narrow and broad band images recorded under dark skies in northwestern Arizona. At the Lagoon's estimated distance, the picture spans about 30 light-years.

APOD: 2006 January 20 - LL Ori and the Orion Nebula
Explanation: This esthetic close-up of cosmic clouds and stellar winds features LL Orionis, interacting with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged Sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The small, arcing, graceful structure just above and left of center is LL Ori's cosmic bow shock, measuring about half a light-year across. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the upper left corner of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. The beautiful picture is part of a large mosaic view of the complex stellar nursery in Orion, filled with a myriad of fluid shapes associated with star formation.

APOD: 2006 January 6 - The Tarantula Nebula
Explanation: First cataloged as a star, 30 Doradus is actually an immense star forming region in nearby galaxy The Large Magellanic Cloud. The region's spidery appearance is responsible for its popular name, the Tarantula Nebula, except that this tarantula is about 1,000 light-years across, and 180,000 light-years away in the southern constellation Dorado. If the Tarantula Nebula were at the distance of the Orion Nebula (1,500 light-years), the nearest stellar nursery to Earth, it would appear to cover about 30 degrees on the sky or 60 full moons. The spindly arms of the Tarantula Nebula surround NGC 2070, a cluster that contains some of the intrinsically brightest, most massive stars known. Intriguing details of the nebula's core can be seen in this remarkable skyscape, a composite of 31 hours of exposure time. This cosmic Tarantula also lies near the site of the closest recent supernova.

APOD: 2005 November 11 - Mountains of Creation
Explanation: This fantastic skyscape lies at the eastern edge of giant stellar nursery W5, about 7,000 light-years away in the constellation Cassiopeia. An infrared view from the Spitzer Space Telescope, it features interstellar clouds of cold gas and dust sculpted by winds and radiation from a hot, massive star outside the picture (just above and to the right). Still swaddled within the cosmic clouds, newborn stars are revealed by Spitzer's penetrating gaze, their formation also triggered by the massive star. Fittingly dubbed "Mountains of Creation", these interstellar clouds are about 10 times the size of the analogous Pillars of Creation in M16, made famous in a 1995 Hubble Space Telescope view. W5 is also known as IC 1848 and together with IC 1805 it is part of a complex region popularly dubbed the Heart and Soul Nebulae. The Spitzer image spans about 70 light-years at the distance of W5.

APOD: 2005 September 23 - Portrait of RY Tauri
Explanation: A star emerges from its natal cloud of gas and dust in this tantalizing portrait of RY Tauri, a small stellar nursery at the edge of the Taurus molecular cloud, a mere 450 light-years away. Illuminating a region that spans about 2/3 of a light-year, the youthful, central star is large, cool, and known to vary in brightness. Still collapsing, in a few million years the star's winds will likely clear out the gas and dust clouds, as it settles down to become a steady main sequence star like the Sun. What remains could well include a planetary system. The image data for RY Tauri is from the Gemini Observatory, on Mauna Kea, Hawaii -- based on observations proposed by the Astronomy Club of Dorval, Quebec.

APOD: 2005 May 19 - X Ray Stars in the Orion Nebula
Explanation: When our middle-aged Sun was just a few million years old it was thousands of times brighter in x-rays. In fact, it was likely similar to some of the stars found in this false-color x-ray composite of the Orion Nebula region from the Chandra Observatory. The image is centered on bright stars of the nebula's Trapezium star cluster, and while analyzing the Chandra data astronomers have now found examples of young, sun-like stars producing intense x-ray flares. It sounds dangerous, but the situation may actually favor the formation of hospitable planetary systems like our own. Energetic flares can produce turbulence in the planet-forming disks surrounding the stars - preventing rocky earth-like planets from spiraling uncomfortably close to and even falling into their active, young parent stars. About 1,500 light-years away, the Orion Nebula is the closest large stellar nursery. At that distance, this Chandra image spans about 10 light-years.

APOD: 2005 April 25 - The Fairy of Eagle Nebula
Explanation: The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains, the statuesque pillars that remain might be imagined as mythical beasts. Pictured above is one of several striking dust pillars of the Eagle Nebula that might be described as a gigantic alien fairy. This fairy, however, is ten light years tall and spews radiation much hotter than common fire. The greater Eagle Nebula, M16, is actually a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars. The above image in scientifically re-assigned colors was released as part of the fifteenth anniversary celebration of the launch of the Hubble Space Telescope.

APOD: 2005 April 22 - Albert Einstein's Miraculous Year
Explanation: In 1905 Albert Einstein had a miraculous year. One hundred years ago, he wrote four papers which revolutionized our understanding of the Universe. The papers outlined; the idea that light could behave as a quantized particle (a photon), an explanation of the thermal motion of atoms and molecules (at a time when atoms themselves were just theories), a theory reconciling motion and the constant speed of light (Special Relativity), and the idea of mass-energy equivalence (E=mc²). Virtually every facet of our modern exploration of the Universe is touched by his now century old insights, along with his later theory of gravity and space-time - General Relativity. In centennial celebration, consider this thoughtful view of a small telescope beside the Einstein Memorial on the grounds of the National Academy of Sciences in Washington DC, USA. The marble platform at the bronze statue's feet is embedded with a map showing the positions of the planets, sun, moon and stars on the memorial's dedication date, 100 years after Einstein's birth in 1879. Albert Einstein died 50 years ago, on April 18, 1955.

APOD: 2005 February 9 - Heat Shield Impact Crater on Mars
Explanation: Broken metal and scorched Mars make the impact site of Opportunity's heat shield one of the more interesting sites inspected by the rolling robot. Visible on the image left is the conical outer hull of the shattered heat shield expelled by Opportunity as it plummeted toward Mars last year. Scrolling right will show not only another section of the heat shield but the impact site itself. The site is of interest partly because its creation was relatively well understood. The impact splattered subsurface light red dirt, while a darker material appears to track toward the large debris. Behind the impromptu space exhibit lies a vast alien landscape of featureless plains and rust-tinted sky.

APOD: 2005 January 31 - NGC 2467: From Gas to Stars
Explanation: One might guess that the group of stars on the left is responsible for shaping the gas cloud on the right -- but it probably is not. Observations of many of the stars in the NGC 2467 show them to be more a superposition of loose groups of stars at different distances than a coherent open cluster of stars energizing the nebula. Still, the above image captures various stages of star formation. The stars at the far left have already formed and their birth nebulae have already dispersed. At the lower left lies a very young star that is breaking free of its surrounding birth cocoon of gas. On the right of the above image, a bright wall of bright gas glows as it evaporates from the energy of many newly formed bright stars. Toward the center, deep dark lanes of dust hide parts of the nebula that surely are forming new stars. The 8-meter Gemini South Telescope, perched on a mountaintop in Cerro Pachon, Chile, took the above image. NGC 2467 lies toward the southern constellation of Puppis, with many of the stars being about 17,000 light years distant.

APOD: 2005 January 13 - Infrared Trifid
Explanation: The Trifid Nebula, aka M20, is easy to find with a small telescope, a well known stop in the nebula rich constellation Sagittarius. But where visible light pictures show the nebula divided into three parts by dark, obscuring dust lanes, this penetrating infrared image reveals filaments of luminous gas and newborn stars. The spectacular false-color view is courtesy of the Spitzer Space Telescope. Astronomers have used the Spitzer infrared image data to count newborn and embryonic stars which otherwise can lie hidden in the natal dust and glowing clouds of this intriguing stellar nursery. As seen here, the Trifid is about 30 light-years across and lies only 5,500 light-years away.

APOD: 2004 October 22 - SOFIA's Mirror
Explanation: The candy-dish appearance of this high-tech astronomical mirror is striking. Made of a special glass ceramic material called Zerodur, it actually measures 2.7 meters across. The transparent surface has not yet received a reflective coating, so the weight-reducing internal honeycomb structure is visible with attractive blue and yellow tints provided by a protective tarp and background lighting. Recently unveiled, the telescope mirror is destined to fly on the Stratospheric Observatory For Infrared Astronomy (SOFIA). Since water vapor in Earth's troposphere tends to block infrared light, SOFIA will operate from a modified Boeing 747 jetliner at altitudes above 40,000 feet. As the largest airborne observatory in the world, SOFIA will explore a host of cosmic environments including sites of star birth and death, the formation of distant solar systems, and black holes in active galaxies.

APOD: 2004 October 6 - N11: A Giant Ring of Emission Nebulas
Explanation: How did this unusually large nebula form? One of the largest nebulas yet detected is actually a complex ring of emission nebulas connected by glowing filaments. The unusual network, known as N11, spans over 1000 light years and is a prominent structure of the Large Magellanic Cloud, the largest satellite galaxy of our Milky Way Galaxy. In the center of the above image is open star cluster LH9, also known as NGC 1760, composed of about 50 bright blue stars that emit radiation that has eroded a hole in their surroundings. A leading hypothesis for the formation of N11 is shells of successive generations of stars being formed further out from the center. The bright region just above center is N11B, an explosive domain where stars are being formed even today.

APOD: 2004 August 28- M17: A Hubble Close-Up
Explanation: Sculpted by stellar winds and radiation, these fantastic, undulating shapes lie within the stellar nursery known as M17, the Omega Nebula, some 5,500 light-years away in the nebula-rich constellation Sagittarius. The lumpy features in the dense cold gas and dust are illuminated by stars off the upper left of the image and may themselves represent sites of future star formation. Colors in the fog of surrounding hotter material indicate M17's chemical make up. The predominately green glow corresponds to abundant hydrogen, with trace sulfur and oxygen atoms contributing red and blue hues. The picture spans about 3 light-years and was released in the thirteenth year of the Hubble Space Telescope's cosmic voyage of exploration.

APOD: 2004 June 3 - Cosmic Construction Zone RCW 49
Explanation: Stars and planets appear to be under construction in dusty nebula RCW 49. This Spitzer Space Telescope false-color infrared view of the nearby stellar nursery shows that known, hot stars are well on their way to clearing out the nebula's central regions. But it also uncovers more than 300 newborn stars, seen here strewn throughout the cosmic dust clouds and filaments. The infrared data indicate the likely presence of protoplanetary discs around some of the infant suns, among the faintest and farthest potential planet-forming discs ever observed. Such exciting results give further support to the idea that planet-forming discs are a natural part of a star's evolution. A mere 14,000 light-years away toward the constellation Centaurus, the industrious RCW 49 is about 350 light-years across.

APOD: 2004 June 1 - The Supergalactic Wind from Starburst Galaxy M82
Explanation: Star formation occurs at a faster pace in M82 -- a galaxy with about ten times the rate of massive star birth (and death) compared to our Milky Way. Winds from massive stars and blasts from supernova explosions have created a billowing cloud of expanding gas from this remarkable starburst galaxy. The above scientifically color-coded image highlights the complexity and origin of the plume by combining a wide field image from the WIYN Telescope in Arizona with a smaller high-resolution image from the orbiting Hubble Space Telescope. M82's aspect in optical pictures has led to its popular moniker, the Cigar Galaxy. M82's burst of star formation was likely triggered a mere 100 million years ago in the latest of a series of bouts with neighboring large galaxy M81.

APOD: 2004 April 29 - Titan's X-Ray
Explanation: This June's rare and much heralded transit of Venus will feature our currently brilliant evening star in silhouette, as the inner planet glides across the face of the Sun. But on January 5, 2003 an even rarer transit took place. Titan, large moon of ringed gas giant Saturn, crossed in front of the Crab Nebula, a supernova remnant some 7,000 light-years away. During Titan's transit, the orbiting Chandra Observatory's x-ray detectors recorded the shadowing of cosmic x-rays generated by the Crab's amazing pulsar nebula, pictured above, in a situation analogous to a medical x-ray. The resulting image (inset at left) probes the extent of Titan's atmosphere. So, how rare was Titan's transit of the Crab? While Saturn itself passes within a few degrees of the Crab Nebula every 30 years, the next similar transit is reportedly due in 2267. And since the stellar explosion which gave birth to the Crab was seen in 1054, the 2003 Titan transit may have been the first to occur ... ever.

APOD: 2004 April 15 - Venus and the Pleiades
Explanation: Venus still rules the western skies after sunset as the brilliant evening star. While wandering the ecliptic with its fellow naked-eye planets earlier this month, it passed near the Pleiades star cluster, providing a striking photo opportunity for earthbound skygazers. Cataloged as M45, the Pleiades stars make for a lovely sight on their own, often shown in long exposure images immersed in hazy blue reflection nebulae. In this picture though, recorded on the evening of April 3rd, brilliant Venus closes with the Seven Sisters and overwhelms the light from the delicate cosmic clouds. The view offers a study in contrasts as Venus appears about 700 times brighter than Alcyone, the Pleiades brightest star. With Venus just over 5 light-minutes from Earth, Alcyone and the other Pleiades cluster stars are about 400 light-years distant. Formed out of the contracting nebula which gave birth to the Sun, Venus is also roughly 4.5 billion years old. The stars of the Pleiades are likely aged a mere hundred million years.

APOD: 2004 April 14 - Massive Star Forming Region DR21 in Infrared
Explanation: Deep in the normally hidden recesses of giant molecular cloud DR21, a stellar nursery has been found creating some of the most massive stars yet recorded. The orbiting Spitzer Space Telescope's Infrared Array Camera opened the window into the cloud last year in mid- infrared light. The cloud is opaque to visible light because of dense interstellar dust. Noticeable in the above representative color infrared Spitzer image are huge bubbles, a complex tapestry of dust and gas, and very massive stars. The infrared filaments actually glow because of organic compounds known as PAHs. The intricate patterns are caused by complex interactions between interstellar winds, radiation pressures, magnetic fields, and gravity. The pictured region spans about 75 light years and lies about 6,000 light years distant toward the constellation of Cygnus.

APOD: 2004 April 10 - 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 10 million light-years away, behind a veil of foreground stars in the high and far-off constellation of Cepheus. Looking from the bright core outward along the loose, fragmented spiral arms, the galaxy's colors show a striking change from the yellowish light of old stars in the galaxy's center to young blue star clusters and reddish star forming regions. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, during the 20th century, at least six supernovae, the death explosions of massive stars, were discovered in NGC 6946. In this sharp composite color digital image, a small barred structure is just visible at the gorgeous galaxy's core.

APOD: 2004 March 25 - An Orion of a Different Color
Explanation: Look up into the sky tonight, and even with a good telescope you won't come across a sight quite like this one. It is a familiar object though, the grand stellar nursery known as the Orion Nebula. But the striking picture combines images taken through three separate filters, each designed to record different emission lines - light from Sulfur, Oxygen, and Hydrogen atoms glowing in the tenuous nebular gas. At such low densities, Sulfur and Hydrogen atoms emit red colors while Oxygen glows green. To distinguish their contributions in the final image, Sulfur was assigned to red, Hydrogen to green, and Oxygen to blue, a color scheme used in mapped-color images of other astronomical nebulae as well. While the result is very different from what the eye might see, the image is still both beautiful and scientifically valuable, tracing elements and conditions within the nearby star forming region.

APOD: 2004 March 11 - Henize 206: Cosmic Generations
Explanation: Peering into a dusty nebula in nearby galaxy the Large Magellanic Cloud, infrared cameras on board the Spitzer Space Telescope recorded this detailed view of stellar nursery Henize 206 filled with newborn stars. The stars appear as white spots within the swirls of dust and gas in the false-color infrared image. Near the top, the sweeping telltale arcs of a supernova remnant are also visible, expanding debris from the final explosion of a massive star. The proximity of the ancient supernova indicates that the shockwave from that stellar death explosion itself likely triggered the formation of the new generation of emerging stars, compressing the gas and dust within Henize 206 and continuing the cosmic cycle of star death and star birth. At the distance of the Large Magellanic Cloud, about 163,000 light-years, this image covers an area about 1,000 light-years across.

APOD: 2004 February 19 - McNeil's Nebula
Explanation: It was a clear, cold western Kentucky night on January 23rd as seasoned amateur astronomer Jay McNeil tried out his recently acquired 3-inch refracting telescope by imaging the area around a familiar object, the M78 reflection nebula in Orion. Days later while processing the images, he noted a substantial but totally unfamiliar nebulosity in the region! With a little help from his friends, his amazing discovery is now recognized as a newly visible reflection nebula surrounding a newborn star -- McNeil's Nebula. Pictured here at the center of this close-up, McNeil's Nebula with its illuminating young star at the tip, do not appear in images of the area before September 2003. The emergence of McNeil's Nebula is a rare event to witness and astronomers are eagerly following its development, but Orion will soon lie too close to the Sun in the sky, interrupting further observations for several months. The Orion nebula complex itself is around 1,500 light-years away. At that distance, the above image spans less than 10 light-years.

APOD: 2003 December 9 - NGC 604: Giant Stellar Nursery
Explanation: Stars are sometimes born in the midst of chaos. About 3 million years ago in the nearby galaxy M33, a large cloud of gas spawned dense internal knots which gravitationally collapsed to form stars. NGC 604 was so large, however, it could form enough stars to make a globular cluster. Many young stars from this cloud are visible in the above image from the Hubble Space Telescope, along with what is left of the initial gas cloud. Some stars were so massive they have already evolved and exploded in a supernova. The brightest stars that are left emit light so energetic that they create one of the largest cloud of ionized hydrogen gas known, comparable to the Tarantula Nebula in our Milky Way's close neighbor, the Large Magellanic Cloud.

APOD: 2003 November 15 - LL Orionis: When Cosmic Winds Collide
Explanation: This arcing, graceful structure is actually a bow shock about half a light-year across, created as the wind from young star LL Orionis collides with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the lower right hand edge of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. The complex stellar nursery in Orion shows a myriad of similar fluid shapes associated with star formation, including the bow shock surrounding a faint star at the upper right. Part of a mosaic covering the Great Nebula in Orion, this composite color image was recorded in 1995 by the Hubble Space Telescope.

APOD: 2003 November 5 - The Lynx Arc
Explanation: While chasing the spectrum of a mysterious arc in a cluster of galaxies within the obscure northerly constellation Lynx, astronomers have stumbled upon the most massive and distant star-forming region ever discovered. The notably red "Lynx arc" lies right of center in this color image of the galaxy cluster, a composite of Hubble Space Telescope and ground-based data. While the galaxy cluster lies about 5 billion light-years distant, spectroscopic studies show that the arc itself is actually a distorted image of an even more distant but enormous star-forming region. The image is formed as the closer galaxy cluster's gravity bends light like a magnifying lens, an effect explained by Einstein's theory of gravity. In fact, the monster star-forming region is nearly 12 billion light-years away and about a million times brighter than the more familiar stellar nursery, the Orion Nebula. Estimates are that the star-forming region seen as the Lynx arc contains about a million massive, hot stars, compared to the four stars which power the Orion Nebula's glow. Stars within the Lynx arc are more than twice as hot as the Orion Nebula's central stars and were formed when the Universe was a mere 2 billion years old. Still, astronomers believe that the first stars were formed at even earlier times.

APOD: 2003 October 2 - Reflections on the 1970s
Explanation: The 1970s are often overlooked. In particular, the beautiful grouping of reflection nebulae NGC 1977, NGC 1975, and NGC 1973 in Orion are often overlooked in favor of the substantial stellar nursery better known as the Orion Nebula. Found along the sword of Orion just north of the bright Orion Nebula complex, these nebulae are also associated with Orion's giant molecular cloud which lies about 1,500 light-years away, but are dominated by the characteristic blue color of interstellar dust reflecting light from hot young stars. In this sharp color image a portion of the Orion Nebula appears along the bottom border with the cluster of reflection nebulae at picture center. NGC 1977 stretches across the field just below center, separated from NGC 1973 (above right) and NGC 1975 (above left) by dark regions laced with faint red emission from hydrogen atoms. Taken together, the dark regions suggest to many the shape of a running man.

APOD: 2003 June 25 - Galaxies in the GOODS
Explanation: This tantalizing view of galaxies scattered near and far is part of the Hubble Space Telescope's contribution to the GOODS - the Great Observatories Origins Deep Survey project. The GOODS' goal is to study galaxy formation and evolution over an unprecedent wide range of cosmic distances, therefore spanning time from the present to the early Universe. Joined by the Chandra X-ray Observatory and soon by the anticipated Space Infrared Telescope Facility along with major ground-based observatories, the project expands greatly on the past Hubble Deep Fields of regions in the northern constellation of Ursa Major and southern constellation Tucana. Across the electromagnetic spectrum, a sample of large nearby galaxies, like the interacting pair at the lower left above, will be compared with distant younger galaxies in a search for clues to the origins of these lighthouses of the cosmos. Preliminary results of the project confirm that the birth rate of stars was higher in the past and that galaxies have indeed been constructed from the "bottom up", growing from mergers and accretion of small infant galaxies to their present day forms.

APOD: 2003 June 10 - Zooming in on the First Stars
Explanation: What became of the first stars? No known stars appear to be composed of truly primordial gas -- all of the stars around us have too many heavy elements. Our own Sun is thought to be a third generation star, with many second-generation stars seen in globular clusters. This year, however, significant progress is being made on solving this perennial astronomical mystery. Analyses of recent WMAP satellite images of the cosmic microwave background indicate that this primordial light was ionized by a first generation of stars that came and went only 200 million years after the Big Bang. Additionally computer codes are now more-accurately tracking the likely creation and evolution of first stars in the early universe. Pictured above at a scale of one light-month, a computer-generated model resolves the scale of the first stars, indicating clean cocoons that condensed into stars always over 30 times the mass of our Sun. Stars like this quickly fused pristine gas into heavier elements and then exploded, seeding the universe with elements that would become part of the stars we know and, ultimately, ourselves.

APOD: 2003 April 25 - M17: A Hubble Close-Up
Explanation: Sculpted by stellar winds and radiation, these fantastic, undulating shapes lie within the stellar nursery known as M17, the Omega Nebula, some 5,500 light-years away in the nebula-rich constellation Sagittarius. The lumpy features in the dense cold gas and dust are illuminated by stars off the upper left of the image and may themselves represent sites of future star formation. Colors in the fog of surrounding hotter material indicate M17's chemical make up. The predominately green glow corresponds to abundant hydrogen, with trace sulfur and oxygen atoms contributing red and blue hues. The picture spans about 3 light-years and was released to celebrate the thirteenth year of the Hubble Space Telescope's cosmic voyage of exploration.

APOD: 2003 February 7 - Orion on Film
Explanation: Orion, the Hunter, is one of the most easily recognizable constellations in planet Earth's night sky. But Orion's stars and nebulae don't look quite as colorful to the eye as they do in this lovely photograph, taken last month from Vekol Ranch south of Phoenix, Arizona, USA. The celestial scene was recorded in a five minute time exposure using high-speed color print film and a 35mm camera mounted on a small telescope. In the picture, cool red giant Betelgeuse takes on a yellowish tint as the brightest star at the upper left. Otherwise Orion's hot blue stars are numerous, with supergiant Rigel balancing Betelgeuse at the lower right, Bellatrix at the upper right, and Saiph at the lower left. Lined up in Orion's belt (left to right) are Alnitak, Alnilam, and Mintaka all about 1,500 light-years away, born of the constellation's well studied interstellar clouds. And if the middle "star" of Orion's sword looks reddish and fuzzy to you, it should. It's the stellar nursery known as the Great Nebula of Orion.

APOD: 2002 November 2 - NGC 604: Giant Stellar Nursery
Explanation: Scattered within this cavernous nebula, cataloged as NGC 604, are over 200 newly formed hot, massive, stars. At 1,500 light-years across, this expansive cloud of interstellar gas and dust is effectively a giant stellar nursery located some three million light-years distant in the spiral galaxy, M33. The newborn stars irradiate the gas with energetic ultraviolet light stripping electrons from atoms and producing a characteristic nebular glow. The details of the nebula's structure hold clues to the mysteries of star formation and galaxy evolution.

APOD: 2002 October 4 - 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 10 million light-years away, behind a veil of foreground stars in the high and far-off constellation of Cepheus. Looking from the bright core outward along the loose, fragmented spiral arms, the galaxy's colors show a striking change from the yellowish light of old stars in the galaxy's center to young blue star clusters and reddish star forming regions. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, during the 20th century, at least six supernovae, the death explosions of massive stars, were discovered in NGC 6946. In this sharp composite color digital image, a small barred structure is just visible at the gorgeous galaxy's core.

APOD: 2002 June 6 - Cone Nebula Infrared Close-Up
Explanation: After astronauts repaired NICMOS - the Near Infrared Camera and Multi-Object Spectrometer - during the latest Hubble Space Telescope servicing mission, astronomers were quick to turn the sophisticated instrument on the photogenic stellar nursery known as the Cone Nebula. This remarkable NICMOS close-up of the Cone Nebula dramatically confirms that the Hubble's infrared vision has been restored. Gas and dust clouds at the blunted tip of the cone-shaped star-forming region are seen here in false-color covering an area about half a light-year across. Toward the left hand side of the picture, the four bright stars with diffraction spikes are also present in visible light images and are in front of the Cone Nebula, itself 2,500 light-years away. But the fainter stars to their right are embedded in or behind the nebula's obscuring dust clouds and are revealed only in this penetrating infrared view.

APOD: 2002 April 20 - Orion Nebula: The 2MASS View
Explanation: Few astronomical sights excite the imagination like the nearby stellar nursery known as the Orion Nebula. The Nebula's glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1,500 light-years away. This distinctively detailed image of the Orion Nebula was constructed using data from the 2 Micron All Sky Survey or 2MASS. Using telescopes in the Northern and Southern Hemispheres of planet Earth, the 2MASS project has mapped the entire sky in infrared light. The wavelength of infrared light is longer than visible light but more easily penetrates obscuring dust clouds. 2MASS cameras were sensitve to near infrared wavelengths around 2 microns or about 0.00008 inches. Visible light has a wavelength of about 0.00002 inches. Survey observations in three infrared bands were translated to blue, green, and red colors to produce this composite image.

APOD: 2002 March 13 - LL Orionis: When Cosmic Winds Collide
Explanation: This arcing, graceful structure is actually a bow shock about half a light-year across, created as the wind from young star LL Orionis collides with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the lower right hand edge of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. The complex stellar nursery in Orion shows a myriad of similar fluid shapes associated with star formation, including the bow shock surrounding a faint star at the upper right. Part of a mosaic covering the Great Nebula in Orion, this composite color image was recorded in 1995 by the Hubble Space Telescope.

APOD: 2002 February 13 - The Great Nebula in Orion
Explanation: Few astronomical sights excite the imagination like the nearby stellar nursery known as the Orion Nebula. The Nebula's glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1500 light-years away. The Great Nebula in Orion can be found with the unaided eye just below and to the left of the easily identifiable belt of three stars in the popular constellation Orion. The above image has been contrast balanced to bring out Orion's detail in spectacular fashion. Visible simultaneously are the bright stars of the Trapezium in Orion's heart, the sweeping lanes of dark dust that cross the center, the pervasive red glowing hydrogen gas, and the blue tinted dust that reflects the light of newborn stars. The whole Orion Nebula cloud complex, which includes the Horsehead Nebula, will slowly disperse over the next 100,000 years.

APOD: 2001 December 27 - The Incredible Expanding Crab
Explanation: The Crab Nebula is cataloged as M1, the first on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, an expanding cloud of debris from the explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across today, the nebula is still expanding at a rate of over 1,000 kilometers per second. Flipping between two images made nearly 30 years apart, this animation clearly demonstrates the expansion. The smaller Crab was recorded as a photographic image made in 1973 using the Kitt Peak National Observatory 4-meter telescope in 1973. The expanded Crab was made this year with the Kitt Peak Visitor Center's 0.4-meter telescope and digital camera. Background stars were used to register the two images.

APOD: 2001 October 19 - X-Ray Stars and Winds in the Rosette Nebula
Explanation: This mosaic of x-ray images cuts a swath across the photogenic Rosette Nebula, a stellar nursery 5,000 light-years from Earth in the constellation Monoceros, the Unicorn. Constructed from data recorded by the orbiting Chandra X-ray Observatory, the mosaic spans less than 100 light-years and is color coded to show low energies in red and high energy x-rays in blue. At the upper right is the young star cluster NGC 2244, central to the Rosette Nebula itself. The hot outer layers of the massive stars are seen to be copious sources of x-rays, but a diffuse x-ray glow also pervades this cluster of newborn stars. Since these stars are so young (less than few million years old!) the diffuse x-ray emission is thought to be powered by energetic, colliding stellar winds rather than remnants of supernovae explosions, a final act in the life cycle of a massive star. Moving away from the center, south and east across the nebula (upper right to lower left), the hot, blustery environment gives way to dense molecular gas, absorbing low energy x-rays while revealing the penetrating high energy x-rays from embedded stars.

APOD: 2001 May 4 - Protoplanetary Survivors in Orion
Explanation: The Orion Nebula is a nuturing stellar nursery filled with hot young stars and their natal clouds of gas and dust. But for planetary systems, the active star-forming region can present a hazardous and inhospitable birthplace. While the formation of dusty protoplanetary disks seems common in Orion, these Hubble Space Telescope close-up images dramatically reveal the torturous conditions they must face while trying to grow into full-fledged planetary systems. In each case, a central young star is surrounded by a disk substantially wider than our solar system. The disks likely contain material in the process of planet formation. However, withering ultraviolet radiation from one of Orion's nearby hot stars is rapidly destroying the disks -- ultimately creating the comet-shaped clouds of glowing gas seen engulfing the protoplanetary systems. Planet formation must occur quickly here, if at all. Researchers estimate that about 90 percent of Orion's youngest protoplanetary disks will not survive the next 100,000 years.

APOD: 2001 April 3 - New Stars Destroying NGC 1748
Explanation: NGC 1748 cannot contain all the new stars it has formed. The young stars, the most massive of which are bright blue, emit so much energy they are pushing out and dispersing the gas and dust that comprise this star forming nebula. Within only the past hundred thousand years, these stars have altered the bubble-like shape of the nebula and will likely destroy the nebula over the next few million years. Of particular interest is a bright region surrounded by a pink ring of dust and gas visible on the left of the above recently released picture by the Hubble Space Telescope. The center of this region is being evacuated by the wind of the brightest star in the nebula. A lane of cooler dust connects NGC 1748 to a larger more diffuse nebula seen on the right. NGC 1748 spans about 25 light-years in diameter and can be found in our galactic neighbor: the Large Magellanic Cloud.

APOD: 2001 February 20 - Star Forming Region S106
Explanation: Massive star IRS4 is beginning to spread its wings. Born only about 100,000 years ago, material streaming out from this newborn star has formed the nebula dubbed Sharpless 106 Nebula (S106), pictured above. A large disk of dust and gas orbiting Infrared Source 4 (IRS4), visible in dark red near the image center, gives the nebula an hourglass shape. S106 gas near IRS4 acts as an emission nebula as it emits light after being ionized, while dust far from IRS4 reflects light from the central star and so acts as a reflection nebula. Detailed inspection of this representative color infrared image has revealed hundreds of low-mass brown dwarf stars lurking in the nebula's gas. S106 spans about 2 light-years and lies about 2000 light-years away toward the constellation of Cygnus.

APOD: 2000 October 16 - Dust and Gas Surrounding Star R Coronae Australis
Explanation: Young star R Coronae Australis has a dusty home. The dust is so thick on the upper left of the above photograph that little light from background stars comes through. Thinner dust near the stars reflects light from R Coronae Australis (upper right) and neighbor TY Coronae Australis, giving their surroundings a flowing appearance. Were these stars more massive they would emit light energetic enough to ionize much of the nearly invisible surrounding hydrogen gas, causing it to appear bright red. The unusual structure above the center is a Herbig-Haro object, a knot of gas ejected from the star that has impacted surrounding gas. R Coronae Australis is about 500 light-years away, while the region shown is about four light years across.

APOD: 2000 October 7 - Sputnik: Traveling Companion
Explanation: Sputnik means "traveling companion". Despite the innocuous sounding name, the launch of the Earth's first "artificial moon", Sputnik 1, by the Soviet Union on October 4, 1957 shocked the free world, setting in motion events which resulted in the creation of NASA and the race to the Moon. Sputnik 1 was a 184 pound, 22 inch diameter sphere with four whip antennas connected to battery powered transmitters. The transmitters broadcast a continuous "beeping" signal to an astounded earthbound audience for 23 days. A short month later, on November 3, the Soviet Union followed this success by launching a dog into orbit aboard Sputnik 2.

APOD: 2000 October 5 - N81: Star Cradle in the SMC
Explanation: This dramatic Hubble Space Telescope image captures the birth of a cluster of massive stars. The newborn stars are seen just as they emerge from their natal nebula. Only 12 light-years across, the nebula is cataloged as N81 and lies some 200,000 light-years away within a neighboring galaxy known as the Small Magellanic Cloud (SMC). Other nebulae which surround massive star clusters can be a thousand or more light-years across. But, prior to the Hubble observations, it was unknown whether N81 and similar, compact emission nebulae were cradles of single stars or star clusters. In the case of N81, the Hubble data clearly reveal multiple hot stars, some nearly 300,000 times as luminous as the Sun. The colorful image emphasizes graceful arcs of dark interstellar dust and fluorescing gas sculpted by the young stars' energetic winds and radiation.

APOD: 2000 June 13 - The Keyhole Nebula in Infrared
Explanation: About three million years ago, the stars in the Keyhole Nebula began to form. The above picture of the Keyhole Nebula, also known as the Carina Nebula or NGC 3372, shows in infrared light many facets of this dramatic stellar nursery which lies only 9,000 light-years away. Fine dust reflects starlight while being heated and emitting light of its own. Open clusters Trumpler 14 and Trumpler 16 are visible in the lower left and upper right of the nebula. The bright star near Trumpler 14 is called Eta Carinae and is one of the most unusual stars known. A candidate for a supernova in the next few thousand years, Eta Carinae faded from being one of the brightest stars in the sky during the 1800s. Despite intensive study, astronomers remain unsure whether Eta Carinae is part of a binary star system.

APOD: 2000 February 11 - XMM-Newton First Light: X-Rays From The LMC
Explanation: Recently the European Space Agency released this and other spectacular "first light" pictures from its new orbiting x-ray observatory, christened XMM-Newton. A churning region of star birth and death in our small neighboring galaxy, the Large Magellanic Cloud (LMC), this field was one of several chosen to test out XMM-Newton's x-ray imaging capabilities. The picture is a false-colour one in which low energy x-rays are translated to red, medium energy to green, and high energy to blue. Image colours therefore represent the relative million degree temperatures of the x-ray emitting regions, red being the coolest and blue the hottest. Remains of the star that exploded as Supernova 1987a appear here as the white x-ray source at the lower right, while another supernova remnant, cataloged as N157D is the brightest source at the upper left. The bluish arc (near center) also appears to be a supernova remnant whose expanding debris cloud is interacting with the LMC's local interstellar gas.

APOD: 2000 February 4 - X-Ray Stars Of Orion
Explanation: The stars of Orion shine brightly in northern winter skies where the constellation harbors the closest large stellar nursery, the Great Nebula of Orion, a mere 1500 light-years away. In fact, the apparently bright clump of stars near the center of this Chandra X-ray telescope picture of a portion of the nebula are the massive stars of the Trapezium - the young star cluster which powers much of the nebula's visible-light glow. But the sheer number of other stars seen in this X-ray image, which spans about 10 light-years, has surprised and delighted astronomers and this picture was recently touted as the richest field of X-ray sources ever recorded in a single observation. The picture does dramatically illustrate that young stars are prodigious sources of X-rays, thought to be produced in hot stellar coronas and surface flares in a young star's strong magnetic field. Our middle-aged Sun itself was probably thousands of times brighter in X-rays when, like the Trapezium stars, it was only a few million years old. The dark lines through the image are instrumental artifacts.

APOD: October 26, 1999 - 30 Doradus: The Tarantula Nebula
Explanation: 30 Doradus is an immense star forming region in a nearby galaxy known as the Large Magellanic Cloud. Its spidery appearance is responsible for its popular name, the Tarantula Nebula, except that this tarantula is about 1,000 light-years across, and 165,000 light-years away in the southern constellation Dorado. If it were at the distance of the Orion Nebula, the nearest stellar nursery to Earth, it would appear to cover about 30 degrees on the sky or about 60 full moons. The above image was taken with the Big Throughput Camera and is shown in representative colors. The spindly arms of the Tarantula Nebula surround the NGC 2070 star cluster which contains some of the intrinsically brightest, most massive stars known. This celestial Tarantula is also seen near the site of the closest recent Supernova.

APOD: June 1, 1999 - A Gallery of Gravitational Mirages
Explanation: The deeper you peer into the universe, the harder it is to see straight. The reason is that distant galaxies act as gravitational lenses, deflecting light that passes nearby. These deflections result in the distortion of background sources, and in some cases the creation of multiple images. Pictured above, candidate artifacts of gravitational lensing have been found in images from the Medium Deep Survey being done with the Hubble Space Telescope. Background source images that are lensed by foreground galaxies include quasars, appearing as multiple blue smudges, and galaxies, distorted into curving arcs. Unusual and interesting candidates for gravitational lensing include an edge-on galaxy disk which might be acting as a lens (upper left) and an image nicknamed London Underground (far left) which could well be the distortion of a background galaxy into an optical Einstein ring.

APOD: April 7, 1999 - Denizen of the Tarantula Nebula
Explanation: The star cluster at lower right, cataloged as Hodge 301, is a denizen of the Tarantula Nebula. An evocative nebula in the southern sky, the sprawling cosmic Tarantula is an energetic star forming region some 168,000 light-years distant in our neighboring galaxy the Large Magellanic Cloud. The stars within Hodge 301 formed together tens of millions of years ago and as the massive ones quickly exhaust their nuclear fuel they explode. In fact, the red giant stars of Hodge 301 are rapidly approaching this violent final phase of stellar evolution - known as a supernova. These supernova blasts send material and shock waves back into the nebular gas to create the Tarantula's glowing filaments also visible in this Hubble Space Telescope Heritage image. But these spectacular stellar death explosions signal star birth as well, as the blast waves condense gas and dust to ultimately form the next generation of stars inside the Tarantula Nebula.

APOD: July 27, 1998 - N81: Starbirth in the SMC
Explanation: A very young star cluster has been discovered in a neighboring galaxy. The stars found in this cluster, dubbed N81, are so young and massive that they furiously eject matter and light up the surrounding nebula. The ejected stellar winds combine and interact to sculpt beautiful and complex structures. Visible near the center of the above representative-color picture are two of N81's brightest stars. Just above them lies a dark knot of dust and gas where these massive stars probably originated. The home galaxy of this stellar nursery is the Small Magellanic Cloud (SMC) located about 200,000 light-years away.

APOD: June 12, 1998 - Orion Nebula: The 2MASS View
Explanation: Few astronomical sights excite the imagination like the nearby stellar nursery known as the Orion Nebula. The Nebula's glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1,500 light-years away. This distinctively detailed image of the Orion Nebula was constructed using data from the 2 Micron All Sky Survey or 2MASS. Now underway with telescopes in the Northern and Southern Hemispheres of planet Earth, the 2MASS project will map the entire sky in infrared light. The wavelength of infrared light is longer than visible light but more easily penetrates obscuring dust clouds. 2MASS cameras are sensitve to near infrared wavelengths around 2 microns or about 0.00008 inches. Visible light has a wavelength of about 0.00002 inches. Survey observations in three infrared bands were translated to blue, green, and red colors to produce this composite image.

APOD: April 11, 1998 - NGC 604: Giant Stellar Nursery
Explanation: Scattered within this cavernous nebula, cataloged as NGC 604, are over 200 newly formed hot, massive, stars. At 1,500 light-years across, this expansive cloud of interstellar gas and dust is effectively a giant stellar nursery located some three million light-years distant in the spiral galaxy, M33. The newborn stars irradiate the gas with energetic ultraviolet light stripping electrons from atoms and producing a characteristic nebular glow. The details of the nebula's structure hold clues to the mysteries of star formation and galaxy evolution.

APOD: April 8, 1998 - Nabta: Older than Stonehenge
Explanation: In the Sahara Desert in Egypt lie the oldest known astronomically aligned stones in the world: Nabta. Over one thousand years before the creation of Stonehenge, local herders built a stone circle and other structures on the shoreline of a lake that has long since dried up. Over 6000 years ago, stone slabs three meters high were dragged over a kilometer to create the site. Shown above is one of the stones that remains. Little is known about the ultimate purpose of Nabta and the nature of the people who built it.

APOD: March 14, 1998 - A Spiral Galaxy Gallery
Explanation: A progression of beautiful spiral galaxies is illustrated above with three photographs from NASA's Ultraviolet Imaging Telescope (UIT). Flying above the Earth's obscuring layer of atmosphere on the Space Shuttle Columbia during the Astro-1 mission in 1990, UIT's cameras were able to image these distant spirals in the ultraviolet light produced by hot, young stars. These bright stars, newly condensed from gas and dust clouds, give away the location of the spiral arms they are born in. Because they are massive (many times the mass of the Sun), they are shortlived. Dying and fading before they move too far from their birth place they make excellent tracers of spiral structure. From left to right the galaxies are known as M33, M74, and M81 and have progressively more tightly wound spiral arms. Astronomers would classify these as Scd, Sc, and Sb type spirals using a galaxy classification scheme first worked out by Edwin Hubble.

APOD: February 6, 1998 - Happy Birthday Jules Verne
Explanation: Sunday marks the 170th anniversary of the birth of Jules Verne (born in Nantes, France on the 8th of February, 1828). Inspired by a lifelong fascination with machines, Verne wrote visionary works about "Extraordinary Voyages" including such terrestrial travels as Around the World in 80 Days, Journey to the Centre of the Earth, and Twenty Thousand Leagues Under the Sea. In 1865 he published the story of three adventurers who undertook a journey From the Earth to the Moon. Verne's characters rode a "projectile-vehicle" fired from a huge cannon constructed in Florida. Does that sound familiar? A century later, the Saturn V rocket and NASA's Apollo program finally turned this work of fiction into fact, propelling adventuresome trios on what was perhaps Verne's most extraordinary voyage. This stirring floodlit view shows the Apollo 9 space-vehicle atop its Saturn V. Launched from a spaceport in Florida in 1969, the Apollo 9 crew were the first to test all lunar landing hardware in space .

APOD: October 27, 1997 - Closeup of Antennae Galaxy Collision
Explanation: It's a clash of the titans. Two galaxies are squaring off in Corvus and here are the latest pictures. When two galaxies collide, however, the stars that compose them usually do not. This is because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space. But during the slow, hundred million year collision, one galaxy can rip the other apart gravitationally, and dust and gas common to both galaxies does collide. In the above wreckage, dark dust pillars mark massive molecular clouds, which are being compressed during the galactic encounter, causing the rapid birth of millions of stars.

APOD: June 16, 1997 - APOD is Two Years Old Today
Explanation: The first Astronomy Picture of the Day (APOD) appeared two years ago today. Pictured above is a scene surrounding the creation of an early APOD, depicting the famous astronomer Tycho Brahe demonstrating a celestial globe to Emperor Rudolph II. The image of a possible optical counterpart to a gamma-ray burst appears on the back wall. In Tycho's day, humanity discovered the nature of the Earth and the geometry of the Solar System. The times we live in are even more fascinating as we explore the nature of our Solar System and the geometry of our whole universe. APOD continues to chronicle these events by finding, presenting ,and annotating the most important astronomical pictures of our time, and cataloging them in an indexed and searchable archive. Link to APOD and discover the cosmos! With over five million pages served, we thank NASA, Michigan Tech, USRA, and most of all our readers, for their continued support.

APOD: April 27, 1997 - Sputnik: Traveling Companion
Explanation: Sputnik means "traveling companion". Despite the innocuous sounding name, the launch of the Earth's first "artificial moon", Sputnik 1, by the Soviets on October 4, 1957 shocked the free world, setting in motion events which resulted in the creation of NASA and the race to the Moon. Sputnik 1 was a 184 pound, 22 inch diameter sphere with four whip antennas connected to battery powered transmitters. The transmitters broadcast a continuous "beeping" signal to an astounded earthbound audience for 23 days. A short month later, on November 3, the Soviets followed this success by launching a dog into orbit aboard Sputnik 2.

APOD: January 23, 1997 - Twistin' by the Lagoon
Explanation: The awesome spectacle of starbirth produces extreme stellar winds and intense energetic starlight -- bombarding dusty molecular clouds inside the Lagoon Nebula (M8). At least two long funnel shaped clouds, each roughly half a light-year long, have apparently been formed by this activity. They extend from the upper left of this close-up of the bright area of the Lagoon known as 'the Hour Glass'. Are these interstellar funnel clouds actually swirling, twisting analogs to Earthly tornados? It's possible. As energy from nearby young hot stars, like the one at lower right, pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds. Confirmation of tornado-like motions within the Lagoon's stellar nursery could come from new instruments scheduled to be installed on the Hubble Space Telescope (HST) during February's servicing mission. This picture is a recently reprocessed HST image made in 1995 as researchers explored this nearby (5,000 light-year distant) starforming region which lies in the direction of Sagittarius.

APOD: January 19, 1997 - From Eagle's EGGs A Star Is Born
Explanation: Perhaps the most famous astronomical image in recent years reveals newborn stars upon pillars of gas and dust - uncovered as researchers used the Hubble Space Telescope to explore the Eagle Nebula in 1995. This stunning picture provides a first hand glimpse of star birth as evaporating gaseous globules (EGGs) are captured emerging from pillars of molecular hydrogen gas and dust. These pillars, dubbed "elephant trunks," are light years in length and are so dense that interior gas gravitationally contracts to form stars. At each pillars' end, the intense radiation of bright young stars causes low density gas to boil away, leaving stellar nurseries of dense EGGs exposed.

APOD: August 16, 1996 - NGC 604: Giant Stellar Nursery in M33
Explanation: The nebula cataloged as NGC 604 is a giant star forming region, 1500 light years across, in the nearby spiral galaxy, M33. Seen here in a snapshot by the Hubble Space Telescope, over 200 newly formed, hot, massive, stars are scattered within a cavern-like, gaseous, interstellar cloud. The stars irradiate the gas with energetic ultraviolet light stripping electrons from atoms and exciting them - producing a characteristic nebular glow. The details of the nebula's structure hold clues to the mysteries of star formation and its effect on the evolution of galaxies.

APOD: February 11, 1996 - Sputnik: The Traveling Companion
Explanation: Sputnik means "traveling companion". In stark contrast to this innocent sounding name, the launch of the Earth's first "artificial moon", Sputnik 1, by the Soviets on October 4, 1957 shocked the free world, setting in motion events which resulted in the creation of NASA and the race to the Moon. Sputnik I was a 184 pound, 22 inch diameter sphere with four whip antennas connected to battery powered transmitters. The transmitters broadcast a continuous "beeping" signal to an astounded earthbound audience for 23 days. A short month later, on November 3, the Soviets followed this success by launching a dog into orbit aboard Sputnik 2.