omnianasa/nasa-apod-metadata huggingface dataset:
Supernova Remnant and Neutron Star (1996-11-14)
A massive star ends life as a supernova, blasting its outer layers back to interstellar space. The spectacular death explosion is initiated by the collapse of what has become an impossibly dense stellar core. However, this core is not necessarily destroyed. Instead, it may be transformed into an exotic object with the density of an atomic nucleus but more total mass than the sun - a neutron star. Directly viewing a neutron star is difficult because it is small (roughly 10 miles in diameter) and therefore dim, but newly formed in this violent crucible it is intensely hot, glowing in X-rays. Images from the ROSAT X-ray observatory above may offer a premier view of such a recently formed neutron stars' X-ray glow. Pictured is the supernova remnant Puppis A, one of the brightest sources in the X-ray sky, with shocked gas clouds still expanding and radiating X-rays. In the inset close-up view, a faint pinpoint source of X-rays is visible which is most likely the young neutron star, kicked out by the asymmetric explosion and moving away from the site of the original supernova at about 600 miles per second.
Searching For Solar Systems (1996-11-15)
Observational astronomy has recently provided evidence of the existence of massive Jupiter-sized planets orbiting distant suns, protoplanetary disks of gas and dust surrounding newly formed stars, and planetary bodies orbiting exotic stellar corpses known as pulsars. Indeed, the formation of planets seems to be a broader and more varied phenomenon than previously imagined. Are there nearby solar systems with Earth-sized planets as well? Many would answer yes, but small, relatively low mass planets orbiting sunlike stars - which might be capable of supporting life - are extremely difficult to detect. One possible approach to this daunting observational problem is to regularly monitor the light from many solar-type stars, searching for the slight decrease in brightness which signals the transit of a small planet in front of the stellar disk. A proposal for a space-based instrument to engage in such a program, the Kepler Mission, is illustrated above. In this concept, the monitoring space telescope orbits the Sun, slowly drifting away from Earth. The goal of this mission would be to discover Earth-sized planets in the habitable zone of solar-type stars, taking a step toward answering the profound question - Does life exist on other worlds beyond our Solar System?  Watch the Leonid Meteor Shower this weekend!
The Leonid Meteor Shower (Tonight)
Credit: (1996-11-16)
Tonight thousands of icy rocks will hurl toward Earth in a fascinating display of light called the Leonid Meteor Shower. There is little danger - few will reach the ground. But this year's Leonids could be nothing compared to the Leonids in 1998. Then, the Leonids might rival any meteor storm this century, with peak rates possibly toping 40 per second. Meteor showers result from debris left by passing comets. The Leonids specifically are small pieces of Comet Tempel-Tuttle. In the above series of time-lapse, 1-minute exposures, a 1995 Leonid is seen to leave a train of hot air that glowed persistently for several minutes.
A Quasar in the Gamma-Ray Sky (1996-11-17)
The bright object in the center of the false color image above is quasar 3C279 viewed in gamma-rays, photons with more than 40 million times the energy of visible light. Like all quasars, 3C279 is a nondescript, faint, starlike object in the visible sky. Yet, in June of 1991 a gamma-ray telescope onboard NASA's orbiting Compton Gamma Ray Observatory unexpectedly discovered that it was one of the brightest objects in the gamma-ray sky. Shortly after this image was recorded the quasar faded from view at gamma-ray energies. Astronomers are still trying to understand what causes these enigmatic objects to flare so violently. Another quasar, 3C273, is faintly visible above and to the right of center.
Unusual M82: The Cigar Galaxy
Credit and Copyright: (1996-11-18)
Something strange happened to this galaxy, but what? M82 is a nearby galaxy in the group of galaxies dominated by itself, M81, and NGC 3077. M82 is thought by some to be limping away from a close encounter with M81. This galactic collision might have stirred up the inner stars and gas in M82, causing the unusual dark lanes of dust visible in the above photograph. M82 is a starburst galaxy with a very active center containing star clusters far brighter than any in our own Milky Way Galaxy.
Fractal Interstellar Dust Up-Close
Credit and Copyright: (1996-11-19)
Our universe is a very dusty place. Dust usually shows its presence by blocking out light emitted from stars or nebula behind it, sometimes creating the illusion of a horse's head or a sombrero hat. But nobody really knows what a typical interstellar dust grain looks like. By studying how dust absorbs, emits, and reflects light, astronomers do know that interstellar dust is much different than the cell and lint based dust found around a typical house. Interstellar dust grains are composed mostly of carbon, silicon, and oxygen and are usually less than about 1/1000 of a millimeter across. Recent work indicates that most dust grains are not spherical. The above picture shows the result of a fractal adhesion model for dust grains involving random conglomerates of spherical compounds of different properties, here artificially highlighted by different colors.
Europa Full Face
Credit: (1996-11-20)
What mysteries might be solved by peering into this crystal ball? This crystal ball is quite unusual because it is actually a moon of Jupiter, the crystals are ice-crystals, and the ball is not only dirty and opaque but cracked beyond repair. Nevertheless, speculation is rampant that oceans exist under these tortured ice-plains that could support life. Europa, the smallest of Jupiter's Galilean moons, was photographed last month in natural color by the robot spacecraft Galileo, now in orbit around Jupiter. The brown patches are what one might think: dirt -- tainting an otherwise white ice-crust.  Europa, nearly the same size as Earth's Moon, similarly keeps one face toward its home planet. The hemisphere of Europa shown above is the one that always trails. Why is Europa's surface the smoothest in the Solar System? Where are Europa's craters?
The Blue Snowball Planetary Nebula
Credit: (1996-11-21)
Will the Sun one day look like - a blue snowball? Maybe! The Blue Snowball is a planetary nebula - and in 5 billion years the Sun will throw off its outer layers and go through a planetary nebula phase. A star can appear "normal" only so long as there are sufficient nuclear reactions in its core. Soon thereafter, gravity will win out and compress the stellar core to higher temperatures. Eventually the core becomes a white dwarf. These high temperatures somehow cause the expulsion of star's outer layers, creating a planetary nebula such as the Blue Snowball pictured above. Although the Blue Snowball, also known as NGC 7662, does appear blue, the above picture's colors are not real and were chosen to highlight the emission of certain ions in the nebula. Many things are still not known about planetary nebula, including details of the physical mechanism that creates the nebula, and the reason for fast knots of gas in the outer regions known as fliers.
Fliers Around the Blue Snowball Nebula
Credit: (1996-11-22)
Planetary nebulae are strange. First, they are gas clouds and have nothing to do with our Solar System's planets. Next, although hundreds of planetary nebulae have been catalogued and thousands surely exist in our Galaxy, aspects of the formation process are still debated. But now yet another mystery has come to light: what created the fast-moving gas clouds that appear around planetary nebula? Dubbed FLIERs for Fast Low-Ionization Emission Regions, these knots of dense gas appear to have been ejected from the central star before it cast of the planetary nebula. Currently, no model can account for either their formation or longevity. In the above false-color picture of NGC 7662, the Blue Snowball Planetary Nebula, the FLIERs are featured in the image inserts.
Gamma Ray Bursts from the Unknown
Credit: (1996-11-23)
Gamma Ray Bursts (GRBs) pose one of the greatest mysteries of modern astronomy. About once a day, the gamma-ray sky lights up with a spectacular explosion. No one knows what causes these explosions or even how far away they are. The above map represents the entire sky in coordinates centered on our Galaxy, the Milky Way. It shows the positions of over 800 of these mysterious bursts of energy detected by the BATSE instrument on board NASA's Compton Gamma Ray Observatory. Before BATSE, most astronomers thought that most GRBs occurred in the disk of our Galaxy, but the above sky map shows little sign of this. The distance scale of GRBs was the topic of a historic debate in April 1995. The positions in the above map are currently being studied in great detail in an effort to uncover a clue about the nature of GRBs. In the above 3B map created by R. Nemiroff, spot size is proportional to peak flux and spot color is indicative of hardness.
Apollo 12 Visits Surveyor 3
Credit: (1996-11-24)
Apollo 12 was the second mission to land humans on the Moon. The landing site was picked to be near the location of Surveyor 3, a robot spacecraft that had landed on the moon three years earlier. Pictured above, Apollo 12 astronauts Conrad and Bean retrieve parts from the Surveyor. The Lunar Module is visible in the distance. Apollo 12 brought back many photographs and moon rocks. Among the milestones made by Apollo 12 was the deployment of the Apollo Lunar Surface Experiments Package, which carried out many experiments including one that measured the solar wind.
A Quasar Portrait Gallery
Credit: (1996-11-25)
QUASARs (QUASi-stellAR objects) lie near the edge of the observable Universe. Discovered in 1963, astronomers were astounded - to be visible at such extreme distances of billions of light-years they must emit prodigious amounts of energy. Where does the energy come from? Many believe the quasar's central engine is a giant black hole fueled by tremendous amounts of infalling gas, dust, and stars. This recently released gallery of quasar portraits from the Hubble Space Telescope offers a look at their local neighborhoods: the quasars themselves appear as the bright star-like objects with diffraction spikes. The images in the center and right hand columns reveal quasars associated with disrupted colliding and merging galaxies which should provide plenty of debris to feed a hungry black hole. Yet, in the left hand column a quasar is seen at the center of an otherwise normal looking spiral (above) and elliptical galaxy. Whatever the secret of the quasar's energy, all these sites must provide fuel for its central engine.
The Radio Sky: Tuned to 408MHz
Credit: (1996-11-26)
Tune your radio telescope to 408MHz (408 million cycles per second) and check out the Radio Sky! You should find that frequency on your dial somewhere between US broadcast television channels 13 and 14. In the 1970s large dish antennas at three radio observatories, Jodrell Bank, MPIfR, and Parkes Observatory, were used to do just that - the data were combined to map the entire sky. Near this frequency, cosmic radio waves are generated by high energy electrons spiraling along magnetic fields. In the resulting false color image, the galactic plane runs horizontally through the center, but no stars are visible. Instead, many of the bright sources near the plane are distant pulsars, star forming regions, and supernova remnants, while the grand looping structures are pieces of bubbles blown by local stellar activity. External galaxies like Centaurus A, located above the plane to the right of center, and the LMC (below and right) also shine in the radio sky.
Storm Clouds Over Jupiter
Credit: (1996-11-27)
Storm clouds, similar to the familiar cumulonimbus thunderheads of Earth, appear to be present on Jupiter. The mosaic of images above shows the region near the raging edge of Jupiter's Great Red Spot, itself some 2 to 3 Earths wide, as observed by the Galileo spacecraft in June of this year. The false colors represent altitude. Low altitude clouds are blue, high, thick clouds are white and high, thin clouds are pink, with the box at the upper right containing the high cloud features likened to the storm clouds of Earth. Scientists speculate that these features are evidence for an abundance of water in at least some regions of Jupiter's atmosphere. On Earth, atmospheric water vapor plays an important role in driving winds - this could well be true on Jupiter, where winds reach up to 300 miles per hour.
Comet-like Clouds in the Cartwheel Galaxy
Credit: (1996-11-28)
In a cartwheel-shaped galaxy far, far away, huge comet-shaped clouds of gas have been discovered racing through the nucleus at about 700,000 miles per hour. The aptly named Cartwheel Galaxy is actually about 500 million light years distant, its suggestive shape created by a head-on collision with a smaller galaxy. Researchers studying this disrupted galaxy using Hubble Space Telescope data recently discovered immense gaseous structures with heads a few hundred light years across and tails thousands of light years long. The fast moving dense gas clouds appear as blue comet-like shapes, mostly along the upper edge of the nucleus, in this false color close-up of the Cartwheel's central region. Their shape, like a boat's bow wave, was probably created by the dense clouds moving through less dense material.
Io: The Fissure King?
Credit: (1996-11-29)
Is Io the solar system's Fissure King? Well, probably not ... but it is the most active volcanic moon. Active volcanoes on Jupiter's moon Io were a surprise discovery of the Voyager missions of the late 1970s. The extent of Io's volcanic activity today is being investigated close-up by the Galileo spacecraft currently exploring the Jovian system. The two frames above show a roughly 300 mile square area around the Io volcano called Marduk. The left-hand view of Marduk was made by Voyager in 1979, the right-hand view by Galileo earlier this year. A comparison reveals that dramatic changes have occured, including the creation of a dark, linear feature running diagonally through the Galileo image that is probably a huge volcanic fissure.
Aurora Astern
Credit: (1996-11-30)
Sailing upside down, 115 nautical miles above Earth, the crew of the Space Shuttle Endeavour made this spectacular time exposure of the southern aurora (aurora australis) in October of 1994. The aurora, also known as the northern and southern lights, appear as luminous bands or streamers of light which can extend to altitudes of 200 miles. They are typically visible from the Earth's surface at high latitudes and are caused by high energy particles from the Sun. The delicate colors are caused by energetic electrons colliding with oxygen and nitrogen in the atmosphere.  In this picture, the rear structure of the Space Shuttle is visible in the foreground with the vertical tail fin pointed toward Earth. Star trails are visible as small streaks above Earth's horizon.
Star Trails in Northern Skies

Credit and Copyright: (1996-12-01)
As the Earth spins on its axis, the sky seems to rotate around us. This motion produces the beautiful concentric arcs traced out by the stars in this time exposure of the night sky. In the middle of the picture is the North Celestial Pole (NCP), easily identified as the point in the sky at the center of all the star trail arcs. The very short bright trail near the NCP was made by the star Polaris, commonly known as the North Star.
Orion's Star Colors

Credit and Copyright: (1996-12-02)
What determines a star's color? Its temperature. Red stars are cool, with temperatures of around 3,000 kelvins (K), while blue stars are hotter and can have temperatures over 30,000 degrees K. Our own lovely yellow Sun's temperature is a comforting 6,000 K. Differences in star colors are dramatically illustrated in the above photo of the constellation Orion, made using a "star trail step-focus" technique. In this technique, a time exposure is used to create star trails, but during the exposure, the focus is changed in steps. For the brighter stars, the blurred image produces more saturated colors in photographs. At the upper left, the cool red supergiant Betelgeuse stands out from the other, hotter, bluish stars composing the body of the constellation. Bright Rigel, a blue supergiant, is at the lower right.
Cocoon of a New White Dwarf
Credit: (1996-12-03)
Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self. In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all! The above cocoon, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The white dwarf can be seen as the bright dot near the photo's center. Our Sun will eventually become a "white dwarf butterfly", but not for another 5 billion years. The above false color image recently entered the public domain and was post-processed by F. Hamilton.
Ice at the Lunar South Pole
Credit: (1996-12-04)
Ice on the Moon? The prospecting Clementine spacecraft may well have discovered it. In 1994, Clementine spent 70 days in lunar orbit mapping the Moon's surface. Shown above is a dramatically detailed composite view centered on the Lunar South Pole - constructed from 1500 Clementine images. This area contains part of the South Pole-Aitken impact basin, the largest known crater in the solar system, probably caused by the impact of a comet or asteroid. The depth of the basin and crater walls at the Lunar South Pole create the permanent shadow region visible above - hypothesised to be large and cold enough to trap water brought to the moon by cometary impacts as surface ice. Indeed, a recent analysis of Clementine data from this area has found a signature of water ice. Water on the Moon presents exciting possibilities as resource for future lunar exploration.
Io's Giant Volcano Pele
Credit: (1996-12-05)
Io has some very large volcanoes. One of the largest is evident near the center of the above photograph and named Pele, for the mythological Polynesian fire goddess. The Galileo spacecraft now orbiting Jupiter took this picture of Jupiter's most active moon in June, although it was released just last week. Evident around Pele is a large red ring, thought to be evidence of recent volcanic activity. The red color indicates the presence of Sulfur, although how the Sulfur was produced is not precisely known.
Globular Cluster M3
Credit and Copyright: (1996-12-06)
This huge ball of stars predates our Sun. Long before mankind evolved, before dinosaurs roamed, and even before our Earth existed, ancient globs of stars condensed and orbited a young Milky Way Galaxy. Of the 250 or so globular clusters that survive today, M3 is one of the largest and brightest, easily visible in the Northern hemisphere with binoculars. M3 contains about half a million stars, most of which are old and red. The existence of young blue stars in M3 once posed a mystery, but these blue stragglers are now thought to form via stellar interactions.
Planetary Systems Now Forming in Orion
Credit: (1996-12-07)
How do planets form? Astronomers are finding out by studying one of the most interesting of all astronomical nebulae known, the Great Nebula in Orion. Insets to above mosaic show several planetary systems in formation. The bottom left insert shows the relative size of our own Solar System. The Orion Nebula contains many stellar nurseries. These nurseries contain hydrogen gas, hot young stars, proplyds, and stellar jets spewing material at high speeds. Much of the filamentary structure visible in this image are actually shock waves - fronts where fast moving material encounters slow moving gas. Some shock waves are visible near one of the bright stars in the lower left of the picture. The Orion Nebula is located in the same spiral arm of our Galaxy as is our Sun.
Degas Ray Crater on Mercury
Credit: (1996-12-08)
Like the Earth's Moon, Mercury is scarred with craters, testifying to an intense bombardment during the early history of the Solar System. In 1974, the Mariner 10 spacecraft surveyed this innermost planet up close, producing the only detailed images of its tortured surface. In the above mosaic the bright rays emanating from the 27 mile wide Degas crater almost appear to be painted on. The rays consist of light colored material blasted out during the crater's formation. Numerous smaller, younger craters are seen superposed on the Degas crater itself.
Callisto Full Face
Credit: (1996-12-09)
Callisto's surface shows its age. While probably formed at the same time as Io, the difference between the surfaces of these two moons of Jupiter could hardly be greater. Io's surface is young, shows practically no impact craters, and is continually being repaved by the lava exploding from its many large volcanoes. Callisto's surface is old, shows the highest density of impact craters in the Solar System, and harbors no volcanoes or even any large mountains. Callisto's surface is one large ice-field, laced with cracks and craters from billions of years of collisions with interplanetary debris. The high-resolution vertical band in the above mosaic was taken by the robot spacecraft Galileo currently orbiting Jupiter. The rest of the mosaic was compiled from pictures taken by the Voyager spacecraft which passed the Callisto in 1979.
Comet Halley's Nucleus
Credit: (1996-12-10)
Here is what a comet nucleus really looks like. For all active comets except Halley, it was only possible to see the surrounding opaque gas cloud called the coma. During Comet Halley's most recent pass through the inner Solar System in 1986, however, spacecraft Giotto was able to go right up to the comet and photograph its nucleus. The above image is a composite of hundreds of these photographs. Although the most famous comet, Halley achieved in 1986 only 1/10th the brightness that Comet Hyakutake did last year, and a similar comparison is likely with next year's pass of Comet Hale-Bopp. Every 76 years Comet Halley comes around again, and each time the nucleus sheds about 6 meters of ice and rock into space. This debris composes Halley's tails and leaves an orbiting trail that, when falling to Earth, are called the Orionids Meteor Shower.
Starburst Ring in Galaxy NGC 1317
Credit: (1996-12-11)
Where do stars form? A typical place is an area of dense nebular gas common to arms in spiral galaxies. Sometimes, however, a burst of star formation can occur with unusual geometry. Nearby galaxy NGC 1317 shows such an unusual ring of star formation surrounding its barred nucleus.  In the above image, older stars appear more red and are more evident in the leftmost photograph in visible light. The rightmost photograph taken by the Ultraviolet Imaging Telescope is in ultraviolet and highlights stars which are younger and bluer and shows the starbirth ring. This unusual ring may be evidence of a gravitational encounter with another galaxy, causing a density wave to ripple out from the galaxy's center.