omnianasa/nasa-apod-metadata huggingface dataset:
Ancient Craters of Southern Rhea (2008-05-13)
Saturn's ragged moon Rhea has one of the oldest surfaces known.  Estimated as changing little in the past billion years, Rhea shows craters so old they no longer appear round � their edges have become compromised by more recent cratering.   Like Earth's Moon, Rhea's rotation is locked on Saturn, and the above image shows part of Rhea's surface that always faces Saturn.  Rhea's leading surface is more highly cratered than its trailing surface.   Rhea is composed mostly of water-ice but is thought to include about 25 percent rock and metal.  The above image was taken by the robot Cassini spacecraft now orbiting Saturn.   Cassini swooped past Rhea last month and captured the above image from about 350,000 kilometers away.  Rhea spans 1,500 kilometers making it Saturn's second largest moon after Titan.  Several surface features on Rhea remain unexplained including large light patches like those seen near the image top.
A Supply Ship Docks with the International Space Station (2008-05-14)
Looking out a window of the International Space Station brings breathtaking views.  Visible vistas include a vast and colorful Earth, a deep dark sky, and an occasional spaceship sent to visit the station.  Visible early last month was a Soyuz TMA-12 spacecraft carrying not only supplies but also three newcomers.   The three new astronauts were Expedition 17 commander Sergei Volkov, flight engineer Oleg Kononenko, and spaceflight participant So-yeon Yi.  Yi returned to Earth a few days later, while Volkov and Konenenko are scheduled to return in a few months.   The docking module pictured above involved the Pirs Docking Compartment.   The Expedition 17 crew, including NASA flight engineer  Gregory Chamitoff, will carry out repairs on the ISS, explore new methods of living in space, and conduct research in space including the effects of space radiation on vitamin molecules.
Sideways Galaxy NGC 3628 (2008-05-15)
Dark dust lanes cut across the middle of this gorgeous island universe, a strong hint that NGC 3628 is a spiral galaxy seen sideways. About 35 million light-years away in the northern springtime constellation Leo, NGC 3628 also bears the distinction of being the only member of the well known Leo triplet of galaxies not in Charles Messier's famous catalog. Otherwise similar in size to our Milky Way Galaxy, the disk of NGC 3628 is clearly seen to fan out near the edges. A faint arm of material also extends to the left in this sharp and deep view of the region. The distorted shape and faint tidal tail suggest that NGC 3628 is interacting gravitationally with the other spiral galaxies in the Leo triplet, M66 and M65.
Circles in the Sky (2008-05-16)
Gazing skyward on a sunny day in May, photographer Jean-Marc Lecleire captured this engaging display of ice halos forming complete circles in the sky. Recorded with a fish-eye lens from a spot near the grand Château de Chambord in France, the picture looks straight up, spanning almost 180 degrees from horizon to horizon. Surrounding the Sun is a halo formed by sunlight refracting through hexagonal-shaped ice crystals in high, thin clouds. The halo is circular and exactly 22 degrees in radius, but it looks squashed because of the distortion of the extremely wide-angle lens. Surrounding the zenith (the point directly above the observer) and always at the same altitude as the Sun is a lovely parhelic circle, caused by sunlight reflecting from ice crystals with nearly vertical faces. On average more common than rainbows, beautiful ice halos can often be seen in planet Earth's sky by those who know how to look for them.
Logarithmic Spirals (2008-05-17)
Uncomfortably close Typhoon Rammasun (right) and 25 million light-year distant galaxy M101 don't seem to have much in common. For starters, Rammasun was only a thousand kilometers or so across while M101 (aka the Pinwheel Galaxy) spans about 170,000 light-years, making them vastly dissimilar in scale, not to mention the different physical environments that control their formation and development. But they do look amazingly alike: each with arms exhibiting the shape of a simple and beautiful mathematical curve known as a logarithmic spiral, a spiral whose separation grows in a geometric way with increasing distance from the center. Also known as the equiangular spiral, growth spiral, and Bernoulli's spiral or spira mirabilis, this curve's rich properties have fascinated mathematicians since its discovery by 17th century philosopher Descartes. Intriguingly, this abstract shape is much more abundant in nature than suggested by the striking visual comparison above. For example, logarithmic spirals can also describe the tracks of subatomic particles in a bubble chamber, the arrangement of sunflower seeds and, of course, cauliflower.
On the Origin of Gold (2008-05-18)
Where did the gold in your jewelry originate?  No one is completely sure.  The relative average abundance in our Solar System appears higher than can be made in the early universe, in stars, and even in typical supernova explosions.  Some astronomers have recently suggested that neutron-rich heavy elements such as gold might be most easily made in rare  neutron-rich explosions such as the collision of neutron stars.  Pictured above is an artist's illustration depicting two neutron stars spiraling in toward each other, just before they collide.  Since neutron star collisions are also suggested as the origin of short duration gamma-ray bursts, it is possible that you already own a souvenir from one of the most powerful explosions in the universe.
Flying Over the Columbia Hills of Mars (2008-05-19)
What it would be like to fly over Mars? Combining terrain data from the orbiting Mars Reconnaissance Orbiter spacecraft with information about the robotic Spirit rover currently rolling across Mars has resulted in a digital movie that shows what a flight over the Columbia Hills might look like.  Dark rippled sand dunes are highlighted against the Columbia Hills in the above opening image.  Clicking on the above image, though, will launch you across Mars, approaching the Columbia Hills.  On the far side of the hills, the dark sand dunes come into view.   Soon you pass an unusual white-rimmed structure, slightly raised, known as Home Plate, the origin of which is currently unknown and being researched.  Turning, you re-approach the hills from a different angle, this time zooming in on Spirit, a curious alien rover sent from planet Earth.  A final zoom pans out over the region.  This coming Sunday, NASA's Phoenix Lander will attempt to set down near the icy North Pole of Mars and search for signs of ancient life.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.