omnianasa/nasa-apod-metadata huggingface dataset:
Mercury in Stereo: Craters Within Craters (1997-01-12)
This Stereo image pair of craters on on Mercury was produced using data from NASA's robot explorer Mariner 10 which performed three close flybys of the Sun's closest companion, two in 1974 and one in 1975. However, the spacecraft was not equipped with a Stereo camera! Instead, the Stereo pair was created using two images of the same region each recorded from a slightly different angle. The image on the left was actually taken during the first flyby, the one on the right during the second. A crater within a crater is visible at the upper left, the outer one is about 70 miles in diameter. The embedded craters themselves are within the 230 mile wide Dostoevsky crater - a segment of Dostoevsky's rim runs through the lower half of the image. To get the 3D Stereo effect, your left eye should see only the left image and your right eye only the right one. (Try placing one edge of a piece of paper on the screen between the pictures and touching your nose to the other edge while viewing.)
Sunspots: Magnetic Depressions (1997-01-13)
Our Sun has spots! These spots appear dark in photographs like the one above, but in fact sunspots are quite bright - they are just dark compared to the rest of the Sun. Sunspots are about the size of the Earth and frequently occur in groups, as shown above. Sunspots occur when a concentrated portion of the Solar magnetic field pokes through the surface. This field slows energy from entering the sunspot region, causing sunspots to appear cooler, darker, and lower than the surrounding surface. Sunspots typically last about a month or two before dissipating. The number of sunspots is always changing, generally going from a maximum to a minimum about every 5 ½ years. In fact, the Sun just passed a minimum last year. The Sun and sunspots should never be looked at directly.
Black Holes in Galactic Centers (1997-01-14)
Do all galaxies have black holes at their centers? Although not even a single galaxy has yet been proven to have a central black hole, the list of candidates has increased yet again. Recent results by astronomers using the Hubble Space Telescope now indicate that most - and possibly even all - large galaxies may harbor one of these dense beasts. In all the galaxies studied, star speeds continue to increase closer the very center. This in itself indicates a center millions of times more massive than our Sun is needed to contain the stars. This mass when combined with the limiting size make the case for the central black holes. Will we ever know for sure?
Black Holes Signature From Advective Disks
Research Credit: (1997-01-15)
What does a black hole look like? If alone, a black hole would indeed appear quite black, but many black hole candidates are part of binary star systems. So how does a black hole binary system look different from a neutron star binary system? The above drawings indicate it is difficult to tell! Recent theoretical work, however, has provided a new way to tell them apart: advective accretion flows (ADAFs). A black hole system so equipped would appear much darker than a similar neutron star system. The difference is caused by the hot gas from the ADAF disk falling through the event horizon of the black hole and disappearing - gas that would have emitted much light were the central object only a neutron star. Recent observations of the soft X-ray transient V404 Cyg has yielded a spectrum much like an ADAF onto a black hole - and perhaps brighter than allowable from an ADAF onto a neutron star.
Trapezium: Teardrops in My Skies
Credit: (1997-01-16)
Sometimes the unexpected comes in a familiar shape. In this recently released picture, the seemingly familiar teardrop-shaped object just right of center is actually an unusually situated disk of gas and dust.  In fact, the teardrop is about the size of our own Solar System and is racing against time to condense and form planets. This disk, however, is unfortunate enough to lie in the Trapezium, which is also home to several immense, bright stars. These bright stars emit light so powerful it boils away the gas and dust in planet-forming disks. Large Jupiter-like planets will probably never form in this hostile environment, but it is currently unknown whether Earth-like planets could form and survive.
Europa: The Latest From Galileo (1997-01-17)
Today, NASA revealed recent results from the Galileo Probe's December 19th flyby of Europa, Jupiter's ice-covered moon - including this close-up image of fractured and frozen terrrain. The highest resolution picture ever made of Europa, the snapshot shows a complex array of surface features in a 5.9 x 9.9 mile area near the moon's equatorial region. North is toward the top and the Sun illuminates the region from the right. The image was made from a distance of 2,060 miles. At the upper left are linear criss-crossing ridges and grooves probably caused by movements of the surface ice. Serpentine valleys and lumpy features of unknown origins are also visible. Only a few impact craters are apparent though, implying a geologically young surface. So far, Galileo's findings lend support to the exciting possibility that liquid water once existed and may still exist beneath Europa's surface.
M16: Nebula With Star Cluster (1997-01-18)
The photogenic M16 shown above is composed of a young star cluster associated with a spectacular emission nebulae lined with clouds of interstellar dust.  The gorgeous spectacle lies toward the galactic center region, some 7,000 light years distant in the constellation Serpens. Most of the stars in the cluster can be seen offset just above and to the right of the photograph's center. This type of star cluster is called an "open" or "galactic" cluster and typically has a few hundred young bright members. The redness of the surrounding emission nebula gas is caused by electrons recombining with hydrogen nuclei, while the dark regions are dust lanes that absorb light from background sources. The dust absorbs so much light it allows astronomers to determine which stars are inside the nebula and which are in the foreground. Stars are forming within the nebula, also known as the Eagle Nebula.
From Eagle's EGGs A Star Is Born (1997-01-19)
Perhaps the most famous astronomical image in recent years reveals newborn stars upon pillars of gas and dust - uncovered as researchers used the Hubble Space Telescope to explore the Eagle Nebula in 1995. This stunning picture provides a first hand glimpse of star birth as evaporating gaseous globules (EGGs) are captured emerging from pillars of molecular hydrogen gas and dust. These pillars, dubbed "elephant trunks," are light years in length and are so dense that interior gas gravitationally contracts to form stars.  At each pillars' end, the intense radiation of bright young stars causes low density gas to boil away, leaving stellar nurseries of dense EGGs exposed.
Earth Nears Asteroid Toutatis (1997-01-20)
On November 29, 1996 the Earth came within 3.3 million miles of the asteroid Toutatis. Above is a computer simulated picture of this spectacle from the surface of Toutatis (a 2.5 degree field of view looking toward Earth). In Earth's sky, Toutatis appeared only as a faint object moving against a background of stars. Also known as Earth-crossing asteroid 4179, Toutatis is in an eccentric 4 year orbit which moves it from the asteroid belt between Mars and Jupiter to just inside Earth's orbit. When the Earth passed near it in 1992 Toutatis was imaged by radar and seen to be two irregularly shaped lumps, perhaps joined by a narrow neck. This bizarre object is up to 1.5 miles wide, 2.9 miles long, and is tumbling through space. In the year 2004, on September 29, the Earth will pass very near Toutatis, closing to within a million miles (4 times the Earth-Moon distance) - the closest approach predicted for any asteroid or comet between now and 2060.  Studies of Toutatis and other Earth-crossing asteroids help reveal connections between the Solar System's meteorites,main-belt asteroids and comets. These wayward asteroids also offer tantalizing targets for robotic exploration and, over time, represent potential collision hazards for planet Earth!
Journey to the Center of the Galaxy 
Credit: (1997-01-21)
In Jules Verne's science fiction classic A Journey to the Center of the Earth, Professor Hardwigg and his fellow explorers encounter many strange and exciting wonders. What wonders lie at the center of our Galaxy? Astronomers now know of some of the bizarre objects which exist there, like vast dust clouds, bright young stars, swirling rings of gas, and possibly even a large black hole. Much of the Galactic center region is shielded from our view in visible light by the intervening dust and gas. But it can be explored using other forms of electromagnetic radiation, like radio, infrared, X-rays, and gamma rays. This beautiful high resolution image of the Galactic center region in infrared light was made by the SPIRIT III telescope onboard the Midcourse Space Experiment. The center itself appears as a bright spot near the middle of the roughly 1x3 degree field of view, the plane of the Galaxy is vertical, and the north galactic pole is towards the right. The picture is in false color - starlight appears blue while dust is greenish grey, tending to red in the cooler areas.
Galaxy Cluster A2199
Credit: (1997-01-22)
It's bigger than a bread box. In fact, it's much bigger than all bread boxes put together. Abell 2199 is huge. In fact, it is a close, large cluster of galaxies, containing several thousands of galaxies centered around a central dominant galaxy. "Close," however, is only relative to other clusters of galaxies, since light takes about 50 million years to reach us from A2199. All of the fuzzy objects in the above picture are galaxies, but these galaxies do not contain most of the matter in the cluster. By studying clusters like A2199, astronomers conclude that some form of dark matter dominates the motion of the bright galaxies. What, exactly, this dark matter is poses one of the greatest astronomical puzzles of modern times.
Twistin' by the Lagoon (1997-01-23)
The awesome spectacle of starbirth produces extreme stellar winds and intense energetic starlight -- bombarding dusty molecular clouds inside the Lagoon Nebula (M8).  At least two long funnel shaped clouds, each roughly half a light-year long, have apparently been formed by this activity. They extend from the upper left of this close-up of the bright area of the Lagoon known as 'the Hour Glass'. Are these interstellar funnel clouds actually swirling, twisting analogs to Earthly tornados? It's possible. As energy from nearby young hot stars, like the one at lower right, pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds. Confirmation of tornado-like motions within the Lagoon's stellar nursery could come from new instruments scheduled to be installed on the Hubble Space Telescope (HST) during February's servicing mission. This picture is a recently reprocessed HST image made in 1995 as researchers explored this nearby (5,000 light-year distant) starforming region which lies in the direction of Sagittarius.
Supernova 1987a Fireball Resolved
Credit: (1997-01-24)
Ten years ago the most notable supernova of modern times was observed. In February 1987, light reached Earth from a star which exploded in the nearby Large Magellanic Cloud galaxy. Supernova 1987a remains the closest supernova since the invention of the telescope.  The explosion catapulted a tremendous amount of gas, light, and neutrinos into interstellar space. When observed by the Hubble Space Telescope (HST) in 1994, large strange rings were discovered whose origin is still mysterious, although thought to have been expelled even before the main explosion. More recent HST observations shown in the inset, however, have uncovered something actually predicted: the expanding fireball from the exploding star. The above high resolution images resolve two blobs flung out from the central explosion.
M51: The Whirlpool Galaxy
Credit: (1997-01-25)
The Whirlpool Galaxy is a classic spiral galaxy. At only 15 million light years distant, M51, also cataloged as NGC 5194, is one of the brighter and more picturesque galaxies on the sky. The smaller galaxy appearing here above and to the right is also well behind M51, as can be inferred by the dust in M51's spiral arm blocking light from this smaller galaxy. Astronomers speculate that M51's spiral structure is primarily due to it's gravitational interaction with this smaller galaxy.
Aurora and Orion
Credit: (1997-01-26)
Looking toward the south from low Earth orbit, the crew of the Space Shuttle Endeavor made this stunning time exposure of the Aurora Australis or southern lights in April of 1994. Aurora are visible at high northern latitudes as well, with the northern lights known as Aurora Borealis. They are caused by high energy electrons from the Solar Wind which are funneled into the atmosphere near the poles by the Earth's magnetic field. The reddish colors occur at the highest altitudes (about 200 miles) where the air is least dense. At lower altitudes and greater densities green tends to dominate ranging to a pinkish glow at the lowest.  The familiar constellation of Orion the Hunter is clearly visible above the dark horizon in the background. Because of the shuttle's orbital motion, the bright stars in Orion appear slightly elongated.
A Prominent Solar Prominence (1997-01-27)
One of the most spectacular solar sights is a prominence. A solar prominence is a cloud of solar gas held above the Sun's surface by the Sun's magnetic field. The Earth would easily fit under one of the loops of the prominence shown in the above picture. A quiescent prominence typically lasts about a month, and may erupt in a Coronal Mass Ejection (CME) expelling hot gas into the Solar System. Although thought by many to be related to the magnetic field, the energy mechanism behind a Solar prominence is still unknown.
Open Cluster M50
Credit and Copyright: (1997-01-28)
Many stars form in clusters. Two types of star clusters are visible in our Milky Way Galaxy: open clusters and globular clusters. Open clusters like M50, shown above, typically contain hundreds of stars, many of which are bright, young, and blue. In fact, most of the bright blue stars in the above picture belong to M50, but most of the dimmer, red stars do not. M50 lies about 3000 light-years from Earth and is about 20 light years across. Open clusters tend to have irregular shapes and are mostly found in the plane of our Galaxy.
NGC 869 & NGC 884: A Double Open Cluster
Credit and Copyright: (1997-01-29)
Most star clusters are singularly impressive. But open clusters NGC 869 and NGC 884 are doubly impressive. Also known as "h and chi Persei", this rare double cluster, shown above, is bright enough to be seen from a dark location without even binoculars. Although their discovery surely predates written history, the "double cluster" was notably cataloged by the Greek astronomer Hipparcos. The clusters are over 7000 light years distant toward the constellation of Perseus, but are separated by only hundreds of light years.
Earth's Temperature
Credit: (1997-01-30)
What's the temperature outside? No matter where you are on Earth, the above map can tell you. This global montage was created using the temperature data from numerous satellites orbiting the Earth. This map indicates temperatures recorded early on January 26th, 1997, but an even more recent map -- updated every 6 hours -- is usually available. For ocean colors on the map, lighter shades of blue indicate warmer temperatures, while for the land, red hues indicate relative warmth. Just looking at the map one can see that summer warms Earth's southern hemisphere, while winter chills Earth's northern hemisphere. The key at the bottom lists temperatures in degrees Centigrade that can be easily converted to degrees Fahrenheit.
Hamlet of Oberon
Credit: (1997-01-31)
What's in a name? Since 1919, the International Astronomical Union has been charged with the task of establishing "conventional" nomenclature for planets, satellites, and surface features. For the remote Uranian system of moons, namesakes from Shakespearean works have been chosen. Thus Oberon, king of the mid-summer night fairies, is also Uranus' most distant and second largest moon and Hamlet is a tragically large and princely crater on its surface. The above image represents known surface features of Oberon and was constructed by the U.S. Geological Survey (USGS) based on data from NASA's robot explorer Voyager 2. Hamlet is the large dark crater to the right of center. In 1986, Voyager 2 flew through the Uranian system - so far it has been the only spacecraft to do so.
Catching Falling Stardust
Credit: (1997-02-01)
This carrot shaped track is actually little more than 5 hundredths of an inch long. It is the trail of a meteroid through aerogel exposed to space by the shuttle launched EURECA (European Recoverable Carrier) spacecraft. The meteoroid itself, about a thousandth of an inch in diameter, is visible where it came to rest, just beyond the tip of the carrot (far right). Chemical analyses of interplanetary dust particles similar to this one suggest that some of them may be bits of comets and represent samples of material from the early stages of the formation of the Solar System. NASA's Stardust mission, planned for launch in 1999, will attempt to directly collect dust from the tail of a comet and return it to Earth -- the first non-lunar sample return mission ever! In addition to peering into the chemistry and history of the solar system, the composition of cometary dust has important implications for the possibility of past life on Mars.
Standing on the Moon
Credit: (1997-02-02)
Humans once walked on the Moon. Pictured above is the second person to stand on the lunar surface: Edwin "Buzz" Aldrin. During this Apollo 11 mission, Neil Armstrong (the first person to walk on the moon) and Buzz Aldrin landed on the Moon while Michael Collins circled in the Command Module above. The lunar team erected a plaque on the surface that reads: HERE MEN FROM THE PLANET EARTH FIRST SET FOOT UPON THE MOON JULY 1969 A.D. WE CAME IN PEACE FOR ALL MANKIND. The Apollo missions demonstrated that it is possible to land humans on the Moon and return them safely.
Stars Without Galaxies
Credit: (1997-02-03)
Galaxies are made up of stars, but are all stars found within galaxies? Apparently not. Using the Hubble Space Telescope, researchers exploring the Virgo Cluster of galaxies have now found about 600 red giant stars adrift in intergalactic space. Above is an artist's vision of the sky from a hypothetical planet of such a lonely sun. The night sky on a world orbiting an intergalactic star would be a stark contrast to Earth's - which features a nightly parade of stars, all members of our own Milkyway galaxy. As suggested by the illustration, a setting swollen red sun would leave behind a dark sky speckled only with faint, fuzzy, apparitions of Virgo Cluster galaxies. Possibly ejected from their home galaxies during galaxy-galaxy collisions, these isolated suns may well represent part of a large, previously unseen stellar population, filling the the space between Virgo cluster galaxies.
Clyde W. Tombaugh: 1906-1997
Credit and Copyright: (1997-02-04)
Astronomer Clyde Tombaugh, discoverer of Pluto, died on January 17th. Inspiring many during his long and exceptional career, he had been living in Las Cruces, New Mexico with his wife of 60 years, Patsy. Today would have been his 91st birthday. He is pictured above in 1995 in his backyard with a telescope he knew well - a 9 inch Newtonian reflector he built in 1927 with discarded farm machinery and car parts. Using this telescope under the dark night skies of Western Kansas, he made drawings of Mars and Jupiter and submitted them to Lowell Observatory in 1928. Hired to work at Lowell in 1929, Tombaugh embarked on a systematic photographic search for the long sought Planet X with a newly constructed 13 inch astrograph. In 1930 Tombaugh triumphed in his struggle to find the 9th planet, discovering faint and distant Pluto orbiting at the edge of our Solar System. Founding father of New Mexico State University's Astronomy Department, he retired as professor emeritus in 1973 but continued to tour as a lecturer and promoter until failing health prevented it. Always an active stargazer, he was asked by the Smithsonian if they could have the telescope he used to make his 1928 drawings. His response: "I told them I was still using it."
Running Red Rings Around Jupiter
Credit: (1997-02-05)
Jupiter has rings, too. Unlike Saturn's bright rings which are composed of chunks of ice, Jupiter's rings are darker and appear to consist of fine particles of rock. The six pictures above were taken in infrared light from the Infrared Telescope Facility in Hawaii in 1994, and cover a time span of two hours. Quite visible are Jupiter's rings, bands and spots in the outer atmosphere. Also visible in the photos, however, are two small Jovian moons. Metis, only 40 kilometers across, appears in the second picture as a dim spot on the rings to the right of Jupiter. Amalthea, much larger and brighter, appears in the third frame on the far left, and can be seen to pass across the face of Jupiter in frames four and five. The origin of Jupiter's rings remains unknown, although hypothesized to be created by material scattered from meteorite impacts onto Jupiter's moons.
Comet Hale-Bopp Returns
Credit and Copyright: (1997-02-06)
Comet Hale-Bopp has returned from behind the Sun. In December and early January, Comet Hale-Bopp was too near the Sun to be easily visible from Earth. Now the comet graces the morning sky and is visible from dark locations even without binoculars. The above photo was taken on January 31st and shows the two emerging tails of Comet Hale-Bopp. The blue wisp pointing up is the ion tale, while the white fuzz is the dust tail. On its trip to the inner Solar System, Comet Hale-Bopp is once again showing signs it could brighten in the next few months to become the most spectacular comet in modern times.
M1: Filaments of the Crab Nebula
Credit and Copyright: (1997-02-07)
The Crab Nebula is filled with mysterious filaments. The Crab Nebula is the result of a star that exploded in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture, the color indicates what is happening to the electrons in different parts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while green indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.
M104: The Sombrero Galaxy
Credit: (1997-02-08)
The famous Sombrero galaxy (M104) is a bright nearby spiral galaxy. The prominent dust lane and halo of stars and globular clusters give this galaxy its name. Something very energetic is going on in the Sombrero's center, as much X-ray light has been detected from it. This X-ray emission coupled with unusually high central stellar velocities cause many astronomers to speculate that a black hole lies at the Sombrero's center - a black hole a billion times the mass of our Sun.