juliensimon/nasa-apod huggingface dataset:
The Perseus Cluster of Galaxies (2008-05-20)

Here is one of the largest objects that anyone will ever see on the sky.  Each of these fuzzy blobs is a galaxy, together making up the Perseus Cluster, one of the closest clusters of galaxies.  The cluster is seen through a foreground of faint stars in our own Milky Way Galaxy.  Near the cluster center, roughly 250 million light-years away, is the cluster's dominant galaxy NGC 1275, seen above as the large galaxy on the image left. A prodigious source of x-rays and radio emission, NGC 1275 accretes matter as gas and galaxies fall into it. The Perseus Cluster of Galaxies is part of the Pisces-Perseus supercluster spanning over 15 degrees and containing over 1,000 galaxies. At the distance of NGC 1275, this view covers about 7.5 million light-years.

Image credit: Jean-Charles Cuillandre
A Dangerous Sunrise on Gliese 876d (2008-05-21)

On planet Gliese 876d, sunrises might be dangerous.  Although nobody really knows what conditions are like on this close-in planet orbiting variable red dwarf star Gliese 876, the above artistic illustration gives one impression. With an orbit well inside Mercury and a mass several times that of Earth, Gliese 876d might rotate so slowly that dramatic differences exist between night and day.  Gliese 876d is imagined above showing significant volcanism, possibly caused by gravitational tides flexing and internally heating the planet, and possibly more volatile during the day.  The rising red dwarf star shows expected stellar magnetic activity which includes dramatic and violent prominences.  In the sky above, a hypothetical moon has its thin atmosphere blown away by the red dwarf's stellar wind. Gliese 876d excites the imagination partly because it is one of the few extrasolar planets known to be close to the habitable zone of its parent star.

Image credit: Inga Nielsen (Hamburg Obs., 
Gate to Nowhere)
Windblown NGC 3199 (2008-05-22)

NGC 3199 lies about 12,000 light-years away, a glowing cosmic cloud in the southern constellation of Carina. The nebula is about 75 light-years across in this haunting, false-color view. Though the deep image reveals a more or less complete ring shape, it does look very lopsided with a much brighter edge at the lower right. Near the center of the ring is a Wolf-Rayet star, a massive, hot, short-lived star that generates an intense stellar wind. In fact, Wolf-Rayet stars are known to create nebulae with interesting shapes as their powerful winds sweep up surrounding interstellar material. In this case, the bright edge was thought to indicate a bow shock produced as the star plowed through a uniform medium, like a boat through water. But measurements have shown the star is not really moving directly toward the bright edge. So a more likely explanation is that the material surrounding the star is not uniform, but clumped and denser near the bright edge of windblown NGC 3199.

Image credit: Ken Crawford
Jupiter's Three Red Spots (2008-05-23)

For about 300 years Jupiter's banded atmosphere has shown a remarkable feature to telescopic viewers, a large swirling storm system known as The Great Red Spot. In 2006, another red storm system appeared, actually seen to form as smaller whitish oval-shaped storms merged and then developed the curious reddish hue.  Now, Jupiter has a third red spot, again produced from a smaller whitish storm. All three are seen in this image made from data recorded on May 9 and 10 with the Hubble Space Telescope's Wide Field and Planetary Camera 2. The spots extend above the surrounding clouds and their red color may be due to deeper material dredged up by the storms and exposed to ultraviolet light, but the exact chemical process is still unknown. For scale, the Great Red Spot has almost twice the diameter of planet Earth, making both new spots less than one Earth-diameter across. The newest red spot is on the far left (west), along the same band of clouds as the Great Red Spot and is drifting toward it. If the motion continues, the new spot will encounter the much larger storm system in August. Jupiter's recent outbreak of red spots is likely related to large scale climate change as the gas giant planet is getting warmer near the equator.
Space Station in the Sun (2008-05-24)

Still bathed in sunlight, the International Space Station tracked through night skies above Hombressen, Germany on May 12. From a range of at least 360 kilometers, astronomer Dirk Ewers was able to record an impressively sharp video sequence of the passage with a small telescope, using some of the individual frames to construct this composite image. Sporting solar arrays, the station's integrated truss structure is nearly 90 meters long. The ATV Jules Verne is docked with the station, while the space station itself is orbiting at aproximately 27,800 kilometers per hour (17,200 mph). A complete video sequence is available as a 1 megabyte mpeg file or avi file.

Image credit: Dirk Ewers
Phoenix Lander Arrives at Mars (2008-05-25)

Will Phoenix survive its landing today on Mars?  Phoenix's landing sequence will ramp up starting at about 7:30 pm EDT (23:30 UTC) today and last just over an hour.  If all goes well, one of Phoenix's first images from Mars will appear on APOD tomorrow.  The Phoenix Lander is programmed to set down near the North Pole of Mars, and, over the next three months, sample alien soil and ice and look for conditions conducive for ancient microbial life. Shown above is an artistic animation of what it might look like to see Phoenix land on Mars.  In the animated sequence, the Phoenix spacecraft arrives at Mars, deploys its braking parachute, jettisons its heat shield, fires it thrusters, lands, unfurls its solar panels, deploys its instruments, scoops up some of Mars, and begins its analysis.

Image credit: MAAS Digital, 
SVV Project, 
NASA
A New Horizon for Phoenix (2008-05-26)

This flat horizon stretches across the red planet as seen by the Phoenix spacecraft after yesterday's landing on Mars. Touching down shortly after 7:30pm Eastern Time, Phoenix made the first successful soft landing on Mars, using rockets to control its final speed, since the Viking landers in 1976. Launched in August of 2007, Phoenix has now made the northernmost landing and is intended to explore the Martian arctic's potentially ice-rich soil. The lander has returned images and data initially indicating that it is in excellent shape after a nearly flawless descent. News updates will be available throughout the day.
Phoenix at Mars (2008-05-27)

The Phoenix lander's footpads are about the size of a dinner plate. One of three is shown at the right, covered with Martian soil after a successful soft landing on the Red Planet on May 25. Amazingly, the left panel image is of the spacecraft during its descent phase, captured by the HiRISE camera onboard Mars Reconnaissance Orbiter -- the first image ever of a spacecraft descending to the surface of another planet. Taken from a range of 750 kilometers, the picture shows Phoenix suspended beneath its unfurling, 10 meter-wide parachute, against the much darker Martian surface. The lander is still attached to its protective backshell. Phoenix released its parachute at an altitude of 12.6 kilometers. Using rockets to further reduce its speed for landing, Phoenix now rests in the northern polar region of Mars at about 68 degrees latitude.
Dark Clouds of the Carina Nebula (2008-05-28)

What dark forms lurk in the mists of the Carina Nebula? These ominous figures are actually molecular clouds, knots of molecular gas and dust so thick they have become opaque.  In comparison, however, these clouds are typically much less dense than Earth's atmosphere.  Pictured above is part of the most detailed image of the Carina Nebula ever taken, a part where dark molecular clouds are particularly prominent.  The entire Carina Nebula spans over 300 light years and lies about 7,500 light-years away in the constellation of Carina. NGC 3372, known as the Great Nebula in Carina, is home to massive stars and changing nebula.  Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically.  Wide-field annotated and zoomable versions of the larger image composite are also available.
A Fog Bow Over Ocean Beach (2008-05-29)

What is that white arch over the water? What is being seen is a fogbow, a reflection of sunlight by water drops similar to a rainbow but without the colors.  The fog itself is not confined to an arch -- the fog is mostly transparent but relatively uniform.  The fogbow shape is created by those drops with the best angle to divert sunlight to the observer.  The fogbow's relative lack of colors are caused by the relatively smaller water drops.  The drops active above are so small that the quantum mechanical wavelength of light becomes important and smears out colors that would be created by larger rainbow water drops acting like small prisms reflecting sunlight.  The above striking image of a fogbow was taken last week with the Sun behind the photographer.  The rocks in the foreground are part of Ocean Beach in California, USA.

Image credit: Keith C. Langill (missionblvd.com)
Descent of the Phoenix (2008-05-30)

In this sweeping view, the 10 kilometer-wide crater Heimdall lies on the north polar plains of Mars. But the bright spot highlighted in the inset is the Phoenix lander parachuting toward the surface. The amazing picture was captured on May 25th by the HiRISE camera onboard the Mars Reconnaissance Orbiter. Though the lander looks like it might be dropping straight into Heimdall, it is really descending about 20 kilometers in front of the crater, in the foreground of the scene. The orbiter was 760 kilometers away from Phoenix when picture was taken, at an altitude of 310 kilometers. Subsequently the orbiter's camera was also able to image the lander on the surface. The parachute attached to the backshell and the heat shield were identified in the image, scattered nearby. Of course, the Phoenix lander itself is now returning much closer views of its landing site as it prepares to dig into the Martian surface.
A View to the Sunset (2008-05-31)

ch day on planet Earth can have a dramatic ending as the Sun sets below the colorful western horizon. Often inspiring, or offering a moment for contemplation, a sunset is perhaps the single most photographed celestial event. Did you recognize this as a picture of one? The image actually is a single exposure of the setting Sun recorded near Wasserberg, Germany on May 11. To create the uncommon sunset view the photographer used a digital camera and a zoom lens (a lens with an adjustable focal length). During the 1/6 second long exposure he smoothly changed the focal length while simultaneously rotating the camera, altering the image scale and orientation. The result transforms an objective depiction of nature into an artistic abstraction.

Image credit: Stefan Seip
A Twisted Solar Eruptive Prominence (2008-06-01)

Ten Earths could easily fit in the "claw" of this seemingly solar monster.  The monster, though, visible on the lower left, is a huge eruptive prominence seen moving out from our Sun.  The above dramatic image taken early in the year 2000 by the Sun-orbiting SOHO satellite.  This large prominence, though, is significant not only for its size, but its shape.  The twisted figure eight shape indicates that a complex magnetic field threads through the emerging solar particles.  Differential rotation inside the Sun might help account for the surface explosion.  Although large prominences and energetic Coronal Mass Ejections (CMEs) are relatively rare, they are occurred more frequently near Solar Maximum, the time of peak sunspot and solar activity in the eleven-year solar cycle.
Unusual Light Patch Under Phoenix Lander on Mars (2008-06-02)

Is that ice under the Phoenix spacecraft on Mars?   Quite possibly.  Phoenix, which landed a week ago, was expected to dig under the Martian soil to search for ice, but the lander's braking rockets may already have uncovered some during descent. Pictured above is an image taken last week by the Robotic Arm Camera showing the unusual light-colored substance just in front of Phoenix's landing pad. Over the next few weeks, Phoenix will continue to photograph its surroundings, analyze the composition of this hard light substrate, and dig into the surrounding soil.  Were the unusual light substrate indeed Martian ice, it would give Phoenix a convenient pedestal to investigate the history of water on Mars, and to better determine whether the boundary between ice and soil was ever capable of supporting life.
The Dark River to Antares (2008-06-03)

Connecting the Pipe Nebula to the bright star Antares is a flowing dark cloud nicknamed the Dark River.  The murkiness of the Dark River is caused by absorption of background starlight by dust, although the nebula contains mostly hydrogen and molecular gas.  Antares, the bright star that appears yellow just below the center of the frame, is embedded in the colorful Rho Ophiuchi nebula clouds.  The Dark River, pictured above across the upper left, spans over 20 times the angular diameter of the Moon and lies about 500 light years distant.  Other types of nebulas visible here include red emission nebula and the blue reflection nebula.

Image credit: M�ximo Ruiz
Chasing the ISS (2008-06-04)

Bathed in sunlight, the International Space Station (ISS) arced through the evening sky above the town of Lauffen in southern Germany on May 31st. The timing of the bright passage was about 10 minutes after the launch of the Space Shuttle Discovery on the STS-124 mission from Kennedy Space Center, Florida, in the southeastern US.  Of course, Discovery was headed toward an orbital rendezvous with the ISS. In chasing after the space station, the shuttle also made a pass over Lauffen just 21 minutes after launch. With a camera fixed to a tripod, astronomer Jürgen Michelberger recorded both magnificent machines streaking overhead in two different time exposures, each about 2 minutes long, and merged them in this composite view. Parallax causes the paths of the ISS (right) and Discovery (near center) to seem to diverge as they were at very different altitudes. Stars (and bright planets) leave two, separated, short trails. The brief, flaring track of an Iridium satellite and faint dotted trail of a passing airplane are also visible. A close inspection will reveal a dim reddish track, the jettisoned external fuel tank, just left of Discovery. Placing your cursor over the picture should help identify some of the features.

Image credit: Jürgen Michelberger
Spitzer's Milky Way (2008-06-05)

The Spitzer Space Telescope's encompasing infrared view of the plane of our Milky Way Galaxy is hard to appreciate in just one picture. In fact, more than 800,000 frames of data from Spitzer's cameras have now been pieced together in an enormous mosaic of the galactic plane - the most detailed infrared picture of our galaxy ever made. The small portion seen here spans nearly 8 degrees, roughly the apparent width of your fist held at arms length, across the galaxy's center. The full mosaic is 120 degrees wide. Highlighted in the false-color presentation are curving green filaments of light from complex molecules - polycyclic aromatic hydrocarbons (PAHs) - that on Earth are the common, sooty products of incomplete combustion. The PAHs are found in star forming regions, along with reddish emission from graphite dust particles. Blue specks throughout the picture are individual Milky Way stars.
Two-Armed Spiral Milky Way (2008-06-06)

Gazing out from within the Milky Way, our own galaxy's true structure is difficult to discern. But an ambitious survey effort with the Spitzer Space Telescope now offers convincing evidence that we live in a large galaxy distinguished by two main spiral arms (the Scutum-Centaurus and Perseus arms) emerging from the ends of a large central bar. In fact, from a vantage point that viewed our galaxy face-on, astronomers in distant galaxies would likely see the Milky Way as a two-armed barred spiral similar to this artist's illustration. Previous investigations have identified a smaller central barred structure and four spiral arms. Astronomers still place the Sun about a third of the way in from the Milky Way's outer edge, in a minor arm called the Orion Spur. To locate the Sun and identify the Milky Way's newly mapped features, just place your cursor over the image.
June's Young Crescent Moon (2008-06-07)

Serene skyviews were enjoyed across planet Earth earlier this week with a young crescent Moon low in the western sky just after sunset. Recorded on June 4, this colorful example includes a quiet beach in the foreground with the city lights of Lisbon, Portugal, and the Sintra Mountains along the horizon. Posing between cloud banks, the Moon's slender, sunlit arc represents only about 1 percent of the full lunar disc. The rest of the Moon's nearside is faintly visible though, illuminated by Earthshine. A waxing crescent Moon should also create some lovely western skies at dusk this weekend. The bright star in the sky near tonight's (Saturday's) Moon will actually be the planet Mars. On Sunday the Moon will move closer to a pair of celestial beacons, bright star Regulus and Saturn.

Image credit: Miguel Claro
Mars Soil Sample Ready to Analyze (2008-06-08)

What surprises are hidden in the soils of Mars? To help find out, the Phoenix Lander Phoenix Lander  which arrived on Mars two weeks ago has attempted to place a scoop of soil in Phoenix's Thermal and Evolved-Gas Analyzer (TEGA).  Pictured above, the dirt-filled scoop approaches one of TEGA's eight ovens. Once in the oven, a soil material will be baked and the emitted gasses categorized by a mass spectrometer.  Quite possibly, some of the light colored material visible in the scoop has the same composition as the light material imaged near the foot of the Lander, which may be ice.  Phoenix is scheduled to spend the next three months digging, baking and chemically analyzing its immediate surroundings to better understand Mars and whether the boundary between ice and soil was ever capable of supporting life.
Saturn's Rings from the Other Side (2008-06-09)

What do Saturn's rings look like from the other side?  From Earth, we usually see Saturn's rings from the same side of the ring plane that the Sun illuminates them. Geometrically, in the above picture taken in April by the robot Cassini spacecraft now orbiting Saturn, the Sun is behind the camera but on the other side of the ring plane.  This vantage point, specifically 17 degrees above the ring plane, gives a breathtaking views of the most splendid ring system in the Solar System. Strangely, the rings have similarities to a photographic negative of a front view. The ring brightness as recorded from different angles indicates ring thickness and particle density of ring particles. Elsewhere, ring shadows can be seen on the sunlit face of Saturn, shown sporting numerous cloud structures in nearly true color.
A Fire Rainbow Over New Jersey (2008-06-10)

What is that inverted rainbow in the sky?  Sometimes known as a fire rainbow for its flame-like appearance, a circumhorizon arc is created by ice, not fire.   For a circumhorizon arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds are present.  Furthermore, the numerous, flat, hexagonal ice-crystals that compose the cirrus cloud must be aligned horizontally to properly refract sunlight like a single gigantic prism.  Therefore, circumhorizon arcs are quite unusual to see.  Pictured above, however, a rare fire rainbow was captured above trees in Whiting, New Jersey, USA in late May.

Image credit: Paul Gitto
(Arcturus Observatory)
Dextre Robot at Work on the Space Station (2008-06-11)

What's the world's most complex space robot doing up there?  Last week, Dextre was imaged moving atop the Destiny Laboratory Module of the International Space Station (ISS), completing tasks prior to the deployment of Japan's Kibo pressurized science laboratory. Dextre, short for the Canadian-built Special Purpose Dextrous Manipulator, has arms three meters in length and can attach power tools as fingers.  Behind Dextre is the blackness of space, while Earth looms over Dextre's head.  The Kibo laboratory segment being deployed during space shuttle Discovery's trip to the ISS can be pressurized and contains racks of scientific experiment that will be used to explore many things, including how plants brace themselves against gravity, and how water might be inhibited from freezing in cells under microgravity.    News: GLAST spacecraft reaches orbit
Phoenix and the Snow Queen (2008-06-12)

A flat, smooth, shiny feature dubbed the Snow Queen is near the top of this color mosaic of the surface beneath the Phoenix Mars Lander. Recorded with the lander's robotic arm camera as it was maneuvered to look under the lander, the region also includes a leg and plate-sized footpad. An intriguing detail near the footpad at about the 2 o'clock position, is a metal spring partially buried in martian soil, a piece of the arm's now opened biobarrier. The smooth Snow Queen feature is strongly suspected to be ice originally just under the soil, uncovered by the thruster rockets as Phoenix set down on the north polar plains of Mars. In fact, the apparent holes or depressions in the Snow Queen's otherwise flat surface are located just under the thrusters.
At Last, GLAST (2008-06-13)

Rising through a billowing cloud of smoke, this Delta II rocket left Cape Canaveral Air Force Station's launch pad 17-B Wednesday at 12:05 pm EDT. Snug in the payload section was GLAST, the Gamma-ray Large Area Space Telescope, now in orbit around planet Earth. GLAST's detector technology was developed for use in terrestrial particle accelerators. But from orbit, GLAST can study gamma-rays from extreme environments in our own Milky Way galaxy, as well as supermassive black holes at the centers of distant active galaxies, and the sources of powerful gamma-ray bursts. Those cosmic accelerators achieve energies not attainable in earthbound laboratories. GLAST also has the sensitivity to search for signatures of new physics in the relatively unexplored high-energy gamma-ray regime.
M51 Hubble Remix (2008-06-14)

The 51st entry in Charles Messier's famous catalog is perhaps the original spiral nebula - a large galaxy with a well defined spiral structure also cataloged as NGC 5194. Over 60,000 light-years across, M51's spiral arms and dust lanes clearly sweep in front of its companion galaxy (right), NGC 5195. Image data from the Hubble's Advanced Camera for Surveys has been reprocessed to produce this alternative portrait of the well-known interacting galaxy pair. The processing has further sharpened details and enhanced color and contrast in otherwise faint areas, bringing out dust lanes and extended streams that cross the small companion, along with features in the surroundings and core of M51 itself. The pair are about 31 million light-years distant. Not far on the sky from the handle of the Big Dipper, they officially lie within the boundaries of the small constellation Canes Venatici.
Phoenix Digs for Clues on Mars (2008-06-15)

What's a good recipe for preparing Martian soil? Start by filling your robot's scoop a bit less than half way.  Next, dump your Martian soil into one of your TEGA ovens, being sure to watch out for clumping.  Then, slowly increase the temperature to over 1000 degrees Celsius over several days.  Keep checking to see when your soil becomes vaporized.  Finally, your Martian soil is not ready for eating, but rather sniffing The above technique is being used by the Phoenix Lander that arrived on Mars three weeks ago.  Data from the first batch of baked soil should be available in a few days. Pictured above, a circular array of the Phoenix Lander's solar panels are visible on the left, while a scoop partly filled with Martian soil is visible on the right.  The robotic Phoenix Lander will spend much of the next three months digging, scooping, baking, sniffing, zapping, dissolving, and magnifying bits of Mars to help neighboring Earthlings learn more about the hydrologic and biologic possibilities of the sometimes mysterious red planet.