juliensimon/nasa-apod huggingface dataset:
The Milky Way Over Mauna Kea (2009-01-27)

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

Image credit: Wally Pacholka
A Partial Eclipse Over Manila Bay (2009-01-28)

What's happened to the setting Sun?  An eclipse! Two days ago, the Moon eclipsed part of the Sun as visible from parts of Africa, Australia, and Asia.  In particular the above image, taken from the Mall of Asia seawall, caught a partially eclipsed Sun setting over Manila Bay in the Philippines.  Piers are visible in silhouette in the foreground.  Eclipse chasers and well placed sky enthusiasts captured many other interesting and artistic images of the year's only annular solar eclipse, including movies, eclipse shadow arrays, and rings of fire. Another partial solar eclipse will be visible from the Philippines in July.  That event, however, will likely be better remembered as a total solar eclipse visible to those occupying a long thin swath of Earth that starts in India and extends through China into the Pacific Ocean.

Image credit: Armando Lee 
(Astron. League Philippines),
F. Naelga Jr., 
100 Hours of Astronomy 
(IYA2009)
Eclipse Shirt 2009 (2009-01-29)

Of course, everyone is concerned about what to wear to a solar eclipse. This is a great example though, especially for the first eclipse of the International Year of Astronomy 2009. In the picture, recorded during the January 26 solar eclipse from the grounds of the South African Astronomical Observatory at Cape Town, repeated images of the eclipse adorn a well-chosen shirt. The effect is familiar to eclipse enthusiasts as small gaps, commonly between leaves on trees, act as pinhole cameras to generate multiple recognizable images of the eclipse. From the Cape Town perspective, the solar eclipse was a partial one, with a maximum of about 65% of the Sun covered. But along a track extending across the Indian Ocean and western Indonesia the eclipse became annular, the solar disk briefly appearing as a fiery ring around the silhouetted Moon.

Image credit: SAAO
NGC 1579: Trifid of the North (2009-01-30)

Colorful NGC 1579 resembles the better known Trifid Nebula, but lies much farther north in planet Earth's sky, in the heroic constellation Perseus. About 2,100 light-years away and 3 light-years across, NGC 1579 is, like the Trifid, a study in contrasting blue and red colors, with dark dust lanes prominent in the nebula's central regions. In both, dust reflects starlight to produce beautiful blue reflection nebulae. But unlike the Trifid, in NGC 1579 the reddish glow is not emission from clouds of glowing hydrogen gas excited by ultraviolet light from a nearby hot star. Instead, the dust in NGC 1579 drastically diminishes, reddens, and scatters the light from an embedded, extremely young, massive star, itself a strong emitter of the characteristic red hydrogen alpha light.

Image credit: Don Goldman
Simeis 147: Supernova Remnant (2009-01-31)

It's easy to get lost following the intricate filaments in this detailed image of faint supernova remnant Simeis 147. Also cataloged as Sh2-240 and seen towards the constellation Taurus, it covers nearly 3 degrees (6 full moons) on the sky. That corresponds to a width of 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. The remarkable narrow-band composite image in the Hubble color palette includes emission from hydrogen, sulfur, and oxygen atoms tracing regions of shocked, glowing gas. This supernova remnant has an estimated age of about 40,000 years - meaning light from the massive stellar explosion first reached Earth 40,000 years ago. But this expanding remnant is not the only aftermath. The cosmic catastrophe also left behind a spinning neutron star or pulsar, all that remains of the original star's core.

Image credit: Astro Anarchy
Auroral Corona Over Norway (2009-02-01)

Higher than highest communications tower, higher than highest mountain, higher than highest airplane, lies the realm of the aurora.  Auroras rarely reach below 60 kilometers, and can range up to 1000 kilometers.  Aurora light results from energetic electrons and protons striking molecules in the Earth's atmosphere.  Frequently, when viewed from space, a complete aurora will appear as a circle around one of the Earth's magnetic poles.  This particularly rare purple auroral corona occurred in 2004 high above Harstad, Norway.

Image credit: highest
communications tower
Comet Lulin Approaches (2009-02-02)

How bright will Comet Lulin become? No one knows for sure.  Although it is notoriously difficult to accurately predict the brightness of newly discovered comets, Comet Lulin could well become visible to the unaided eye later this month. As Comet Lulin moves into the northern sky in mid February to rise around midnight, it should at least be spotted by comet watchers with binoculars and a good sky chart.  Tracking observations indicate that the comet officially designated C/2007 N3 (Lulin) has now swung by the Sun and is approaching Earth on a trajectory that will bring it within half the Earth-Sun distance in late February. Comet Lulin's orbit indicates that this is likely the comet's first trip into the inner Solar System. The comet was discovered by Quanzhi Ye of Sun Yat-sen University on images obtained by Chi-Sheng Lin at the Lu-Lin Observatory of National Central University.  In this picture, taken from Italy last Friday, are Comet Lulin's coma and tails, one tail pointing away from the Sun, and an anti-tail -- dust that trails the comet in its orbit and may appear to point toward the Sun.

Image credit: Paolo Candy
Lenticular Clouds Above Washington (2009-02-03)

Are those UFOs near that mountain?  No -- they are multilayered lenticular clouds. Moist air forced to flow upward around mountain tops can create lenticular clouds. Water droplets condense from moist air cooled below the dew point, and clouds are opaque groups of water droplets. Waves in the air that would normally be seen horizontally can then be seen vertically, by the different levels where clouds form.  On some days the city of Seattle, Washington, USA, is treated to an unusual sky show when lenticular clouds form near Mt. Rainier, a large mountain that looms just under 100 kilometers southeast of the city. This image of a spectacular cluster of lenticular clouds was taken last December.

Image credit: Tim Thompson
A Dangerous Summer on HD 80606b (2009-02-04)

On the distant planet HD 80606b, summers might be dangerous. Hypothetic life forms floating in HD 080606b's atmosphere or lurking on one of its (presently hypothetical) moons might fear the 1,500 Kelvin summer heat, which is hot enough not only to melt lead but also nickel.  Although summers are defined for Earth by the daily amount of sunlight, summers on HD 80606b are more greatly influenced by how close the planet gets to its parent star. HD 80606b, about 200 light years distant, has the most elliptical orbit of any planet yet discovered.  In comparison to the Solar System, the distance to its parent star would range from outside the orbit of Venus to well inside the orbit of Mercury.  In this sequence, the night side of HD 80606b is computer simulated as it might glow in infrared light in nearly daily intervals as it passed the closest point in its 111-day orbit around its parent star.   The simulation is based on infrared data taken in late 2007 by the Spitzer Space Telescope.
NGC 604: X-rays from a Giant Stellar Nursery (2009-02-05)

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.
Space Station in the Moon (2009-02-06)

On February 2nd, a first quarter Moon shone in planet Earth's early evening sky. As seen from a location on the US west coast near Mt. Hamilton, California, the International Space Station also arched above the horizon, crossing in front of the Moon's sunlit surface. The space station's transit lasted 0.49 seconds. This sharp exposure, a well-timed telescopic image, recorded the space station during the transit against the background of the Moon's smooth Mare Serenitatis (Sea of Serenity). The orbital outpost was traveling northwest to southeast (from 2 o'clock to 8 o'clock) at a range of 389 kilometers or about 230 miles. Of course, the Moon itself was 1,000 times farther away. In the remarkable photo, the glinting station also offers a hint of the bluish reflection of earthlight.

Image credit: Eric J. Zbinden
Comet Lulin Tails (2009-02-07)

Sweeping through the inner solar system, Comet Lulin is easily visible in both northern and southern hemispheres with binoculars or a small telescope. Recent changes in Lulin's lovely greenish coma and tails are featured in this two panel comparison of images taken on January 31st (top) and February 4th. Taken from dark New Mexico Skies, the images span over 2 degrees. In both views the comet sports an apparent antitail at the left -- the comet's dust tail appearing almost edge on from an earth-based perspective as it trails behind in Lulin's orbit. Extending to the right of the coma, away from the Sun, is the beautiful ion tail. Remarkably, as captured in the bottom panel, Comet Lulin's ion tail became disconnected on February 4, likely buffeted and torn away by magnetic fields in the solar wind. In 2007 NASA satellites recorded a similar disconnection event for Comet Encke. Don't worry, though. Comet tails can grow back.

Image credit: Joseph Brimacombe
Inside the Eagle Nebula (2009-02-08)

From afar, the whole thing looks like an Eagle.  A closer look at the Eagle Nebula, however, shows the bright region is actually a window into the center of a larger dark shell of dust.  Through this window, a brightly-lit workshop appears where a whole open cluster of stars is being formed.  In this cavity tall pillars and round globules of dark dust and cold molecular gas remain where stars are still forming.  Already visible are several young bright blue stars whose light and winds are burning away and pushing back the remaining filaments and walls of gas and dust.  The Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with binoculars toward the constellation of the Serpent (Serpens).  This picture combines three specific emitted colors and was taken with the 0.9-meter telescope on Kitt Peak, Arizona, USA.

Image credit: T. A. Rector
Anemic Galaxy NGC 4921 at the Edge (2009-02-09)

How far away is spiral galaxy NGC 4921? Although presently estimated to be about 320 million light years distant, a more precise determination could be coupled with its known recession speed to help humanity better calibrate the expansion rate of the entire visible universe.  Toward this goal, this image was taken by the Hubble Space Telescope in order to help identify key stellar distance markers known as Cepheid variable stars.   Since NGC 4921 is a member of the Coma Cluster of Galaxies, refining its distance would also allow a better distance determination to one of the largest nearby clusters in the local universe. The magnificent spiral NGC 4921 has been informally dubbed anemic because of its low rate of star formation and low surface brightness. The remarkably sharp image was made with Hubble's Advanced Camera for Surveys, currently in need of repair. Visible in the image are, from the center, a bright nucleus, a bright central bar, a prominent ring of dark dust, blue clusters of recently formed stars, several smaller companion galaxies, unrelated galaxies in the far distant universe, and unrelated stars in our Milky Way Galaxy.
Orion's Belt (2009-02-10)

Alnitak, Alnilam, and Mintaka, are the bright bluish stars from east to west (left to right) along the diagonal in this gorgeous cosmic vista. Otherwise known as the Belt of Orion, these three blue supergiant stars are hotter and much more massive than the Sun. They lie about 1,500 light-years away, born of Orion's well-studied interstellar clouds. In fact, clouds of gas and dust adrift in this region have intriguing and some surprisingly familiar shapes, including the dark Horsehead Nebula and Flame Nebula near Alnitak at the lower left. The famous Orion Nebula itself lies off the bottom of this star field that covers about 4.5x3.5 degrees on the sky. This image was taken last month with a digital camera attached to a small telescope in Switzerland, and better matches human color perception than a more detailed composite taken over 15 years ago.

Image credit: Martin Mutti,  
Astronomical Image Data
Archive
Orion's Belt Continued (2009-02-11)

Yesterday's skyscape featured Alnitak, Alnilam, and Mintaka, the stars of Orion's Belt. Today's also presents the easternmost belt star, Alnitak, at the bottom right of the field, surrounded by the well-known Horsehead and Flame nebulae. But this view sweeps farther to the east (left) and north (top) detailing subtler cosmic clouds of gas and dust scattered through the fertile, nebula rich region. The scene is anchored at the top left by the eerie blue glow and ominous dark dust lanes of reflection nebula M78. Like the Horsehead, the Flame, and the Orion Nebula itself, M78 is a readily visible part of the large Orion Molecular Cloud complex some 1,500 light-years distant.

Image credit: Alan Smallbone
Zodiacal Light Vs. Milky Way (2009-02-12)

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

Image credit: Daniel López
Circle 'round the Moon (2009-02-13)

If your sister-in-law phoned you at 1am to tell you there was a circle around the Moon, how would you react? When it happened to him early last Sunday morning, photographer Laurent Laveder, grabbed his equipment and ran outside! He was rewarded with the sight of a bright lunar halo shining in his neighborhood skies above Quimper, France. With a radius of 22 degrees, the beautiful halo is produced by the refraction of moonlight in hexagonal-shaped ice crystals formed in thin, high clouds. Laveder captured a series of digital images that he used to create this composite fisheye view as well as a remarkable 360 degree VR panorama.

Image credit: PixHeaven.net
IC 1805: The Heart Nebula (2009-02-14)

Sprawling across almost 200 light-years, emission nebula IC 1805 is a mix of glowing interstellar gas and dark dust clouds. Derived from its Valentine's-Day-approved shape, its nickname is the Heart Nebula. About 7,500 light-years away in the Perseus spiral arm of our galaxy, stars were born in IC 1805. In fact, near the cosmic heart's center are the massive hot stars of a newborn star cluster also known as Melotte 15, about 1.5 million years young. A little ironically, the Heart Nebula is located in the constellation Cassiopeia. From Greek mythology, the northern constellation is named for a vain and boastful queen.  This deep view of the region around the Heart Nebula, cropped from a larger mosaic, spans about 2.5 degrees on the sky or about 5 times the diameter of the Full Moon.

Image credit: Daniel Marquardt
Antarctic Ice Shelf Vista (2009-02-15)

It's all gone but the mountains.  Most of the sprawling landscape of ice that lies between the mountains visible above has now disintegrated.  The above picture was taken in Antarctica from the top of Grey Nunatak, one of three Seal Nunatak mountains that border the Larsen B Ice-Shelf.  The other two nunataks are visible in the picture taken in 1994.  Over the past several years large chunks of the 200-meter thick Larsen B Ice-Shelf have been breaking off and disintegrating.  The cause is the local high temperatures of recent years, part of a planet wide climate change called  global warming.  Over the past few years, the area that has disintegrated is roughly the size of Luxembourg.  As ice-shelves break up, they unblock other ice sheets that fall onto the ocean, raising sea levels everywhere.  Scientists are watching the much-larger Ross Ice Shelf, which, if it fully collapses, could cause global sea levels to rise five meters over the next few hundred years.

Image credit: Helmut Rott (U. Innsbruck)
The Great Carina Nebula (2009-02-16)

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).
Unusual Red Glow Over Minnesota (2009-02-17)

What in heaven's blazes is that? When landing in Minneapolis, Minnesota, USA in 2002, just before his flight ascended above cloud level in the early evening, passenger Tyler Blessing saw and photographed "huge curved sheets of glowing light extending from cloud to ground." The glow appeared unlike other unusual lights more typically seen, including crepuscular rays, anticrepuscular rays and the glory. A leading possibility, mentioned initially by the photographer, is that the light sheets are setting sunlight scattered off of falling rain.  Alternatively, the phenomenon could just be a peculiar window reflection. APOD readers, who have previously shown an impressive ability to pool their collective intelligence to create a better understanding of photographed sky anomalies, are invited to discuss this online. It might help to know that EXIF data indicates that the image was captured on 2002 September 23 at about 8:07 pm in the evening (local time), and that the camera was reported to be pointing north of west at that time. The oval on the ground, visible in the lower right of the above image, is Canterbury Downs race track.

Image credit: Tyler Blessing �
Satellites Collide in Low Earth Orbit (2009-02-18)

How often do satellites collide? Although minuscule space debris may strike any satellite on occasion, the first known collision between time two full satellites occurred only last week. Even though thousands of satellites have been launched, the low collision rate is caused by the great vastness of space. Last week, however, a defunct Russian communications satellite named Cosmos 2251 smashed right into an operational US communications satellite named Iridium 33 over Siberia, Russia.  Both satellites were destroyed.  The sheer number of massive particles in a dispersing debris cloud, depicted in an inset image above, increases the risk that other operating satellites might be struck by a harmful fast-moving projectile.  The collision occurred in low Earth orbit only 750 kilometers up, a height shared by many satellites but significantly higher than the 350-km high human-occupied International Space Station.  Since satellites may disintegrate when struck by fast-moving space junk, the crash focuses concern that a future dramatic satellite collision may one day start an ablation cascade of increasingly more collisions.  The result could then render future human space flights increasingly risky and expensive satellite lifetimes increasingly short.

Image credit: Analytical Graphics, Inc.
Mauna Kea Milky Way Panorama (2009-02-19)

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

Image credit: Wally Pacholka