juliensimon/nasa-apod huggingface dataset:
Unusual Silica Rich Soil Discovered on Mars (2007-12-18)

You're rolling across Mars when you unexpectedly uncover some unusually light soil.   You stop. You turn. You return to inspect the soil and find out it is almost purely silica -- the main ingredient in quartz and glass.  Such soil has never been found on Mars before. What created this soil?  Since you are the robotic rover Spirit currently rolling across Mars, you send the images and data back to Earth for analysis.  Your scientist friends from the blue water planet say that such soil on Earth is usually created by either volcanic steam or a hot spring.  The second hypothesis in particular indicates, once again, a wet past for part of Mars, as possibly hot water saturated with silica deposited the white soil.  Intriguingly, on Earth, living microbes typically flourish under either condition.  Pictured above, the uncovered light soil is visible on the right.   APOD presents: Astronomy Pictures of the Year for 2007
Stars and Dust through Baade's Window (2007-12-19)

Billions of stars light up the direction toward the center of our Galaxy.  The vast majority of these stars are themselves billions of years old, rivaling their home Milky Way Galaxy in age.  Together with interstellar dust, these old stars combine to create this yellowish starscape. Although the opaque dust obscures the true Galactic center in visible light, there is a low density hole in the dust on the right of the image.  The region, named Baade's Window for the German astronomer who studied it, is used to inspect distant stars and to determine the internal geometry of the Milky Way.  Baade's Window lies toward the constellation of the Archer (Sagittarius).   APOD presents: Astronomy Pictures of the Year for 2007

Image credit: Stephane Guisard
Reflections on the 1970s (2007-12-20)

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 presents: Astronomy Pictures of the Year for 2007

Image credit: Martin Pugh
Horizon to Horizon (2007-12-21)

Scroll right and journey from horizon to horizon as your gaze sweeps through the zenith in the night sky over Beg-Meil, France. Recorded on December 13th, the entertaining panorama (image key) covers 210 degrees in 21 separate exposures, beginning on the beach with bright star Sirius rising in the southeast. Look up (pan right) to encounter the nebula rich constellation of Orion and continue on to find the lovely Pleiades star cluster. Farther along, higher in the sky, is the famous Comet Holmes, still gracing the northern hemisphere's night with its remarkable expanding coma. Finally, just before diving into the urban glow from city lights along the northwestern horizon (far right), check out the double star cluster in Perseus and take in the cosmic streak of a bright Geminid Meteor.   APOD presents: Astronomy Pictures of the Year for 2007

Image credit: PixHeaven.net
Tyrrhenian Sea and Solstice Sky (2007-12-22)

Today the Solstice occurs at 0608 Universal Time, the Sun reaching its southernmost declination in planet Earth's sky. Of course, the December Solstice marks the beginning of winter in the northern hemisphere and summer in the south. When viewed from northern latitudes, the Sun will make its lowest arc through the sky along the southern horizon. So in the north, the Solstice day has the shortest length of time between sunrise and sunset and fewest hours of daylight.  This striking composite image follows the Sun's path through the December Solstice day of 2005 in a beautiful blue sky, looking down the Tyrrhenian Sea coast from Santa Severa toward Fiumicino, Italy. The view covers about 115 degrees in 43 separate, well-planned exposures from sunrise to sunset.   APOD presents: Astronomy Pictures of the Year for 2007

Image credit: Danilo Pivato
Moon and Mars Tonight (2007-12-23)

The Full Moon and a brilliant, ruddy Mars will share the sky tonight. Skygazers can easily enjoy the celestial pairing as the two are separated by a degree or even less. In fact, seen from parts of northern North America and Europe, the Moon will actually occult (pass in front of) the Red Planet. Mars is so bright because it is near opposition, opposite the Sun in Earth's sky and near its closest approach to planet Earth. But Mars is not nearly as bright as the Moon, also opposite the Sun tonight. In this striking preview of tonight's sky show, backyard astronomer John Harms was able to photograph an almost Full Moon near Mars last month. His simple, single exposure relied on clouds to block some of the overwhelming moonlight.   APOD presents: Astronomy Pictures of the Year for 2007

Image credit: John Harms
Emission Nebula IC 1396 (2007-12-24)

Sprawling across hundreds of light-years, emission nebula IC 1396 mixes glowing cosmic gas and dark dust clouds. Stars are forming in this area, only about 3,000 light-years from Earth. This detailed view was created in light primarily emitted by hydrogen gas, recorded through a filter that narrowly transmits a wavelength characteristic of glowing hydrogen atoms in the nebula. Among the intriguing dark shapes within IC 1396, the winding Elephant's Trunk nebula lies just left center. IC 1396 lies in the high and far off constellation of Cepheus.   APOD presents: Astronomy Pictures of the Year for 2007

Image credit: Kent Wood
Mars and Orion Over Monument Valley (2007-12-25)

Welcome to The World At Night. Sharing the night sky seen around the world, this view from Monument Valley, USA includes a picturesque foreground of famous buttes. Buttes are composed of hard rock left behind after water eroded away the surrounding soft rock.   The two buttes on the image left are known as the Mittens, while Merrick Butte is on the right. Recorded just last week, planet Mars is at the left of the skyscape, a glowing beacon of orange that is the brightest object in the frame.  To the right of Mars lies the constellation of Orion. Betelgeuse is the reddish star near the center and the Belt of Orion and the Orion Nebula are farther right. Finally, the bright blue star Rigel appears above Merrick Butte in this stunning view of  The World At Night.   APOD presents: Astronomy Pictures of the Year for 2007

Image credit: Wally Pacholka 
(Astropics.com)
Trifid Pillars and Jets (2007-12-26)

Dust pillars are like interstellar mountains.  They survive because they are more dense than their surroundings, but they are being slowly eroded away by a hostile environment.  Visible in the above picture is the end of a huge gas and dust pillar in the  Trifid Nebula, punctuated by a smaller pillar pointing up and an unusual jet pointing to the left.  The pink dots are newly formed low-mass stars. A star near the small pillar's end is slowly being stripped of its accreting gas by radiation from a tremendously brighter star situated off the above picture to the upper right.  The jet extends nearly a light-year and would not be visible without external illumination.  As gas and dust evaporate from the pillars, the hidden stellar source of this  jet will likely be uncovered, possibly over the next 20,000 years.   APOD presents: Astronomy Pictures of the Year for 2007
Earth at Twilight (2007-12-27)

No sudden, sharp boundary marks the passage of day into night in this gorgeous view of ocean and clouds over our fair planet Earth. Instead, the shadow line or terminator is diffuse and shows the gradual transition to darkness we experience as twilight. With the Sun illuminating the scene from the right, the cloud tops reflect gently reddened sunlight filtered through the dusty troposphere, the lowest layer of the planet's nurturing atmosphere. A clear high altitude layer, visible along the dayside's upper edge, scatters blue sunlight and fades into the blackness of space. This picture actually is a single digital photograph taken in June of 2001 from the International Space Station orbiting at an altitude of 211 nautical miles.   APOD presents: Astronomy Pictures of the Year for 2007
A Beautiful Boomerang Nebula (2007-12-28)

This symmetric cloud dubbed the Boomerang Nebula was created by a high-speed wind of gas and dust blowing from an aging central star at speeds of nearly 600,000 kilometers per hour.  The rapid expansion has cooled molecules in the nebular gas to about one degree above absolute zero - colder than even the cosmic background radiation - making it the coldest known region in the distant Universe.  Shining with light from the central star reflected by dust, the frigid Boomerang Nebula is believed to be a star or stellar system evolving toward the planetary nebula phase.  This Hubble image was recorded using polarizing filters (analogous to polaroid sunglasses) and color coded by the angle associated with the polarized light.  The gorgeous result traces the small dust particles responsible for polarizing and scattering the light. The Boomerang Nebula spans about one light year and lies about 5,000 light years away toward the constellation Centaurus.   APOD presents: Astronomy Pictures of the Year for 2007
Saturn's Infrared Glow (2007-12-29)

Known for its bright ring system and many moons, gas giant Saturn looks strange and unfamiliar in this false-color view from the Cassini spacecraft. In fact, in this Visual and Infrared Mapping Spectrometer (VIMS) mosaic the famous rings are almost invisible, seen edge-on cutting across picture center. The most striking contrast in the image is along the terminator or boundary between night and day. To the right (day side) blue-green hues are visible sunlight reflected from Saturn's cloud tops. But on the left (night side) in the absence of sunlight, the lantern-like glow of infrared radiation from the planet's warm interior silhouettes features at Saturn's deeper cloud levels.   APOD presents: Astronomy Pictures of the Year for 2007
Mammatus Clouds Over Mexico (2007-12-30)

Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height.  After water droplets form that air becomes an opaque cloud.  Under some conditions, however, cloud pockets can develop that contain large droplets of water or ice that fall into clear air as they evaporate.  Such pockets may occur in turbulent air near a  thunderstorm, being seen near the top of an anvil cloud, for example.  Resulting mammatus clouds can appear especially dramatic if sunlit from the side.  These mammatus clouds were photographed over Monclova, Mexico.   APOD presents: Astronomy Pictures of the Year for 2007

Image credit: Raymundo Aguirre
A Year of Spectacular Comets (2007-12-31)

Two spectacular comets graced Earth's skies during 2007.  Both comets became bright enough to be seen by the unaided eye of the casual sky enthusiast.  Early in 2007, Comet McNaught grew brighter than any comet in 40 years, displaying a beautiful dust tail that flowed across the sky.  Comet McNaught (c/2006 P1) became known as the Great Comet of 2007, sported unusual striations in its expansive dust tail, and showed unexpectedly complex chemistry in its ion tail.   Toward the year's end, normally docile and faint Comet Holmes brightened suddenly and unexpectedly to naked eye visibility.  Remarkably, Comet 17P/Holmes stayed bright for weeks even though it lies beyond the orbit of Mars.  No distant comet in recent history has remained so bright for so long.  In this view, a white Comet Holmes was photographed in early December posing with the Heart and Soul Nebulas.   APOD presents: Astronomy Pictures of the Year for 2007

Image credit: Bob Nanz
(San Diego Astronomy Association)
Rays from an Unexpected Aurora (2008-01-01)

This aurora was a bit of a surprise.  For starters, on this day in 2002, no intense auroral activity was expected at all.  Possibly more surprising, however, the aurora appeared to show an usual structure of green rays from some locations.  In this view, captured from North Dakota, USA, a picket fence of green rays stretches toward the horizon.  Mirroring the green rays is a red band, somewhat rare in its own right.  Lights from the cities of Bismarck and Mandan are visible near the horizon.    Note: A German language mirror of APOD is now available.

Image credit: Lyndon Anderson 
(Prairie Journal)
A Galaxy is not a Comet (2008-01-02)

This gorgeous galaxy and comet portrait was recorded on December 30th, in the skies over Hoogeveen, The Netherlands. The combined series of 60 x 60 second exposures finds the lovely green coma of Comet 8P/Tuttle near its predicted conjunction with the Triangulum Galaxy. Aligning each exposure with the stars shows the comet as a streak, slowly moving against the background stars and galaxy. An alternative composition with exposures centered on the comet, shows the background stars and galaxy as streaks. The alluring celestial scene would also have been a rewarding one for the influential 18th century comet hunter Charles Messier. While Messier scanned French skies for comets, he carefully cataloged positions of things which were fuzzy and comet-like in appearance but did not move against the background stars and so were definitely not comets. The Triangulum Galaxy, also known as M33, is the 33rd object in his famous not-a-comet catalog. The modern understanding holds that the Triangulum Galaxy is a large spiral galaxy some 3 million light-years distant. Comet 8P/Tuttle, just bright enough to be visible to the unaided eye in dark, northern skies, is about 40 million kilometers (2 light-minutes) away.   The Amateur Astronomers Association of New York Presents: APOD Editor's Lecture: January 4th - American Museum of Natural History

Image credit: Emiel Kempen
Geminids in 2007 (2008-01-03)

Dust from curious near-Earth asteroid 3200 Phaethon seems to fall from the constellation Gemini in this fisheye skyview. The composite image was recorded over four December nights (12-15) just last year from Ludanyhalaszi, Hungary. Of course, the streaks are meteor trails from the annual Geminids meteor shower. The work of astronomer Erno Berko, the finished picture combines 113 different frames and captures 123 separate meteors. The Geminids is one of the northern skies most reliably performing meteor showers and did not disappoint last year. Under good conditions some skywatchers reported well over 100 meteors per hour near the December 14/15 peak for the Geminids in 2007. Look up tonight and you might see the 2008 Quadrantids.   The Amateur Astronomers Association of New York Presents: APOD Editor's Lecture: January 4th - American Museum of Natural History

Image credit: Erno Berko
The Milky Way at 5000 Meters (2008-01-04)

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

Image credit: Serge Brunier
M51: Cosmic Whirlpool (2008-01-05)

Follow the handle of the Big Dipper away from the dipper's bowl, until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (right), NGC 5195. The pair are about 31 million light-years distant and officially lie within the boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy in small, earthbound telescopes, this sharpest ever picture of M51 was made in January 2005 with the Advanced Camera for Surveys on board the Hubble Space Telescope.
Jupiter's Rings Revealed (2008-01-06)

Why does Jupiter have rings?  Jupiter's rings were discovered in 1979 by the passing Voyager 1 spacecraft, but their origin was a mystery.  Data from the Galileo spacecraft that orbited Jupiter from 1995 to 2003 later confirmed that these rings were created by meteoroid impacts on small nearby moons.  As a small meteoroid strikes tiny Adrastea, for example, it will bore into the moon, vaporize, and explode dirt and dust off into a Jovian orbit.  Pictured above is an eclipse of the Sun by Jupiter, as viewed from Galileo.  Small dust particles high in Jupiter's atmosphere, as well as the dust particles that compose the rings, can be seen by reflected sunlight.   Note: Meet astronomy bloggers and APOD editor RN in Austin this Tuesday night.
Quadrantid Meteors and Aurora from the Air (2008-01-07)

Where do meteor showers originate?  To help answer this question, astronomers studied in some detail the Quadrantid meteor shower that occurred over this past weekend.  In particular, astronomers with specialized cameras flew as part of the Quadrantid's Multi-Instrument Aircraft Campaign (MAC) aboard a Gulfstream V aircraft above northern Canada over the past few days and studied the Quadrantid meteor shower in unprecedented detail. Pictured above is a composite image combining many short exposures.  Visible in the image are the wingtip of the airplane reflecting a red beacon on the left, green aurora most prominent on the image right, and numerous meteor streaks throughout.  Preliminary indications are that the meteor stream is quite stable in time but variable in meteor abundance.  Over 100 meteors per hour were visible at the peak from the MAC aircraft.   Meteor data from around the world will continue to be analyzed to try to verify Peter Jenniskens's recent hypothesis that minor planet 2003 EH1 is an intermittently active comet and the parent body of the annual Quadrantid meteor shower.   Note: Meet sky enthusiasts, astro bloggers, and APOD editor RN in Austin tomorrow (Tuesday) night.
A Jupiter-Io Montage from New Horizons (2008-01-08)

As the New Horizons spacecraft sweeps through the Solar System, it is taking breathtaking images of the planets.  In February of last year, New Horizons passed Jupiter and the ever-active Jovian moon Io.   In this montage, Jupiter was captured in three bands of infrared light making the Great Red Spot look white.  Complex hurricane-like ovals, swirls, and planet-ringing bands are visible in Jupiter's complex atmosphere. Io is digitally superposed in natural color.  Fortuitously, a plume was emanating from Io's volcano Tvashtar.  Frost and sulfuric lava cover the volcanic moon, while red-glowing lava is visible beneath the blue sunlight-scattering plume.   The robotic New Horizons spacecraft is on track to arrive at Pluto in 2015.   Note: Meet sky enthusiasts, astro bloggers, and APOD editor RN in Austin tonight.
Hidden Galaxy IC 342 from Kitt Peak (2008-01-09)

Beautiful nearby spiral galaxy IC 342 could be more famous if it wasn't so hidden.  A sprawling island universe, IC 342 would be a prominent galaxy in our night sky, but it is almost hidden from view behind the veil of stars, gas and dust clouds in the plane of our Milky Way galaxy. Similar in size to other large, bright spiral galaxies IC 342 is a mere 7 million light-years distant in the long-necked, northern constellation of the Giraffe (Camelopardalis). Even though IC 342's light is dimmed by intervening cosmic clouds, this remarkably sharp telescopic image traces the galaxy's own obscuring dust, blue star clusters, and glowing pink star forming regions along spiral arms that wind far from the galaxy's core. IC 342 may have undergone a recent burst of star formation activity and is close enough to have gravitationally influenced the evolution of the local group of galaxies and the Milky Way.   Note: Astronomy lectures by an APOD editor are now available as a free podcast.

Image credit: T. Rector
Active Galaxy Centaurus A (2008-01-10)

A mere 11 million light-years away, Centaurus A is a giant elliptical galaxy - the closest active galaxy to Earth. This remarkable composite view of the galaxy combines image data from the x-ray ( Chandra), optical(ESO), and radio(VLA) regimes. Centaurus A's central region is a jumble of gas, dust, and stars in optical light, but both radio and x-ray telescopes trace a remarkable jet of high-energy particles streaming from the galaxy's core. The cosmic particle accelerator's power source is a black hole with about 10 million times the mass of the Sun coincident with the x-ray bright spot at the galaxy's center. Blasting out from the active galactic nucleus toward the upper left, the energetic jet extends about 13,000 light-years. A shorter jet extends from the nucleus in the opposite direction. Other x-ray bright spots in the field are binary star systems with neutron stars or stellar mass black holes. Active galaxy Centaurus A is likely the result of a merger with a spiral galaxy some 100 million years ago.
Polaris Dust Nebula (2008-01-11)

Centered on North Star Polaris, this 4 degree wide field of view covers part of a complex of relatively unfamiliar, diffuse dust clouds soaring high above the plane of our Milky Way Galaxy. The combined light of the Milky Way stars are reflected by the dusty, galactic cirrus, the reflected starlight having the same blue tint characteristic of better known reflection nebulae. But this deep color image also records a faint reddish luminescence from the dust grains as they convert invisible stellar ultraviolet radiation to visible red light.  Dubbed extended red emission, the dim cosmic glow is thought to be caused by complex organic molecules known as PAHs (polycyclic aromatic hydrocarbons), common constituents of interstellar dust. On planet Earth, PAHs are widely encountered as the sooty products of combustion.

Image credit: Hidden Valley Observatory
Mercury Chases the Sunset (2008-01-12)

This colorful view of the western sky at sunset features last Wednesday's slender crescent Moon. Of course, when the Moon is in its crescent phase it can never be far from the Sun in the sky. Also always close to the Sun in Earth's sky is innermost planet Mercury, seen here below and right of center against the bright orange glow along the horizon. Mercury is usually difficult to glimpse because of overwhelming sunlight, but increasingly better views of the small planet after sunset will be possible as it wanders farther east of the Sun in the coming days. On January 14th, NASA's MESSENGER spacecraft will have a good view too, as it makes its first Mercury flyby.

Image credit: Doug Zubenel