omnianasa/nasa-apod-metadata huggingface dataset:
The Doomed Dust Disk of NGC 7052 (1998-06-22)
What created the dust disk in the center of NGC 7052, and what keeps it spinning?  Although the disk might appear as a relatively tame "hubcap in space", the unusual center of elliptical galaxy NGC 7052 is probably the remnant of a titanic collision between galaxies.  What's more, the disk's spin indicates the tremendous gravity of a massive central black hole. Analysis of this recently released photo by the Hubble Space Telescope indicates that the disk is thousands of light-years across, rotates faster than 100 kilometers per second, at a distance of 150 light-years from the center, and contains more mass than a million Suns.  The theorized central black hole is thought to be yet 100 times more massive, and may swallow the entire disk in the next few million years.
A Slice Through an Artificial Universe (1998-06-23)
We live in the era of humanity when most of our Universe is being mapped. To help understand these maps, astronomers computationally estimate the appearance of several possible candidate universes, to which maps of the real Universe can be compared.  Pictured above is a slice through one of these artificial universes, displayed so that each part of the universe is seen at the same time after the Big Bang. The above map corresponds to an area nearly ten billion light years across.  Highlighted in red are filaments that each contain thousands of galaxies, while darker regions are nearly devoid of galaxies. Our good-sized Milky Way Galaxy would hardly be visible on this map.
Sparkling Star May Indicate Galactic Composition (1998-06-24)
If a star in this photograph twinkled slightly, would anyone notice? Would anyone care? Astronomers with the MACHO Collaboration noticed one such twinkle just last week, and many members of the astronomical community now care.  The specific type of sparkling of the SMC star in the above cross-hairs clearly indicated a multiple-star microlensing event was in progress.  Microlensing is a rare phenomena where gravity itself deflects light so prominently that background sources might appear to have many images and appear many times their normal brightness.  Study of the precise details of the latter part of this microlensing event might reveal the mass and distance to the lenses.  Were these lenses in the outer reaches of our Galactic halo, this would add evidence to some controversial indications that a good fraction of the normally unseen matter in our Galaxy is composed of lenses only slightly less massive than our Sun.
NGC 4650A: Strange Galaxy and Dark Matter (1998-06-25)
This strangely distorted galaxy of stars is cataloged as NGC 4650A. It lies about 165 million light-years away in the southern constellation Centaurus. The complex system seems to have at least two parts, a flattened disk of stars with a dense, bright, central core and a sparse, sharply tilted ring of gas, dust and stars. Observations show that the stars in the disk and the stars and gas in the ring really do move in two different, nearly perpendicular planes, probably as the result of a past galaxy vs. galaxy collision. The observed motions within both disk and ring also indicate the presence of "dark matter" - an unseen source of gravity which influences the movement of this system's visible stars. Over the decades evidence that our Universe is largely composed of such dark matter has grown while the nature of dark matter has remained a profound astrophysical mystery. The picture was constructed from images made using part of the European Southern Observatory's (ESO) new Very Large Telescope system now undergoing its testing phase.
A Planet For Gliese 876 (1998-06-26)
Centered in this unremarkable, 1/4 degree wide patch of sky in the constellation Aquarius is the star Gliese 876. Gliese 876 is smaller than the Sun, only about 1/3 as massive, and too faint to be seen without a telescope. But it is known to be one of the nearest stars, only 15 light-years distant. Astronomers have just announced findings that imply Gliese 876 has a planet at least 1.6 times as massive as Jupiter - making this now one of the closest suspected planetary systems. Like many recent discoveries, this planet's detection is not based on direct imaging but on spectroscopic measurements of the periodic change in motion or "Doppler wobble" produced in the parent star as the planet orbits. The Doppler wobble of Gliese 876 indicates that its planet orbits once every 61 days at an average distance of about 1/5 the radius of the Earth's orbit.
Southern Neptune (1998-06-27)
Neptune, the Solar System's outermost gas giant planet, is 30 times farther from the Sun than Earth. Twelve years after a 1977 launch, Voyager 2 flew by Neptune and found surprising activity on a planet that receives only 3 percent as much sunlight as Jupiter. In its brief but tantalizing close-up glimpse of this dim and distant world, the robot spacecraft recorded pulses of radio emission, zonal cloud bands, and large scale storm systems with up to 1500 mile per hour winds - the strongest measured on any planet. This mosaic of 5 Voyager images shows Neptune's Southern Hemisphere. Cloud bands and the Earth-sized, late "Great Dark Spot" with trailing white clouds located at about 22 degrees southern latitude are clearly visible.  The distance from the Great Dark Spot feature to Neptune's South Pole (image center) is about 17,000 miles.
Comet Hale-Bopp Over Val Parola Pass (1998-06-28)
In 1997, Comet Hale-Bopp became much brighter than any surrounding stars. It could be seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed last March above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind strike ions expelled from the comet's nucleus. The white dust tail was composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet.  Observations have shown that Comet Hale-Bopp's nucleus spins about once every 12 hours. Comet Hale-Bopp is still visible to those in the right place with a good telescope.
Solar Magnetic Bananas (1998-06-29)
Is that our Sun? The unusual banana-shaped loops shown above are actually part of a computer-generated snap-shot of our Sun's magnetic field.  This animated frame was constructed using data from the ground-based U.S. Solar Vector Magnetograph and the space-based Japanese X-Ray Telescope Yohkoh. Surfaces of constant magnetic field strength loop through the Sun's corona, break through the Sun's surface, and connect regions of magnetic activity such as sunspots.  Recently, contact has been interrupted with the Sun-watching SOHO satellite.  Although SOHO had completed its two year mission, attempts are still being made to re-establish communication.
The Universe Evolves (1998-06-30)
Scroll right and watch the universe evolve.  Above is a computer simulation depicting the evolution of our entire universe.  On the far left is a slice of the universe soon after the Big Bang - over 10 billion years ago.  As time progresses toward the right, the initially smooth universe can be seen becoming more and more clumpy. The vertex near the far right marks the present day.  The largest slice of the universe actually surveyed is simulated to the vertex's right. This artificial universe, called a Hubble Volume, was designed to mimic what humanity might see were we to have powerful enough telescopes.  By comparing different computer simulations to reality, we might be able to better tell what kind of universe we live in.
NGC 1808: A Nearby Starburst Galaxy (1998-07-01)
NGC 1808 is a galaxy in turmoil. A barred spiral with marked similarities to our home Milky Way Galaxy,  NGC 1808 is distinguished by a peculiar nucleus, an unusually warped disk, and strange flows of hydrogen gas out from the central regions.  Amidst all of this, NGC 1808 is undergoing so much star formation it has been deemed a starburst galaxy. In the above color-enhanced photograph, regions of active star formation and shown by their blue glow.  Here bright blue stars have recently formed and are energizing large clouds of surrounding hydrogen gas.  The reddish brown regions indicate dense interstellar dust.  NGC 1808 is a relatively close 40 million light-years away, and stretches about 35,000 light-years across.  The peculiar state of NGC 1808 may be caused by the gravity of neighboring galaxy NGC 1792.
X-ray Transit Of Mercury (1998-07-02)
This sequence of false color X-ray images captures a rare event - the passage or transit of planet Mercury in front of the Sun. Mercury's small disk is silhouetted against the bright background of X-rays from the hot Solar Corona. It appears just to the right of center in the top frame and moves farther right as the sequence progresses toward the bottom. The dark notch is a coronal hole near the Solar South Pole, while a flaring coronal bright point can be seen to the left of the notch in the top frames. The frames were recorded on November 6, 1993 by the Soft X-ray Telescope on board the orbiting Yohkoh satellite. Transits of Mercury (and Venus) were historically used to discover the geometry of the solar system and to map planet Earth itself.
Mir Above (1998-07-03)
Photographed from the approaching Space Shuttle Endeavour, the Mir space station floats above the clouds of planet Earth. Mir's modular construction, bristling with solar panels and antennas, lends it a slightly whimsical, insect-like appearance. Astronaut Andrew Thomas was dropped off at Mir by Endeavour in January and recently picked up by the Space Shuttle Discovery during STS-91, the ninth and last Mir docking mission. Thomas' 4 1/2 month stay culminates the shuttle-Mir program in which seven U.S. astronauts spent a total of 977 days with Russian crews on board Mir. The experience gained will be applied toward the construction of the International Space Station scheduled to begin with launches in November and December 1998.
The Firework Nebula (1998-07-04)
Imaged by the WIYN Telescope, the Firework Nebula is the result of a type of stellar explosion called a nova. In a nova, a nuclear detonation on the surface of a compact white dwarf star blasts away material that has been dumped on its surface by a companion star. Also known as GK Persei or Nova Persei, this nova became one of the brightest stars in the night sky in the year 1901. As it faded, astronomers could see an expanding shell of gas that eventually became this spectacular nebula. While not exactly predictable, GK Per undergoes minor outbursts every three or four years.
Apollo 15's Home on the Moon (1998-07-05)
Could you ever call this place home? The lunar module shown above, named "Falcon," served as home for Apollo 15 astronauts David Scott and James Irwin during their stay on the Moon in July and August 1971. Meanwhile, astronaut Alfred Worden circled in the command module overhead. Harsh sunlight on the grey lunar surface lends the image an eerie quality, while the Lunar Apennine Mountains frame the background. Mount Hadley Delta is visible on the right. Visible in the foreground are tracks from the first Lunar Roving Vehicle, an electric car which enabled the astronauts to explore extended areas on the lunar surface.  Apollo 15 confirmed that most lunar surface features were created by impacts. Rocks returned by the Apollo 15 crew included green glasses whose formation mechanism is still unclear.
Sizzling Io (1998-07-06)
What's cooking on Io? This active moon of Jupiter is marked with volcanoes spewing lava that is now known to be hotter than any lava on Earth.  Above is the highest resolution color-enhanced image yet composed of the most active surface in our Solar System.  Features as small as three kilometers are visible.  Sulfur compounds cause many of Io's unusual colors, while darker regions are probably composed of silicate rock.
M8: The Lagoon Nebula (1998-07-07)
The bright Lagoon Nebula is home to a diverse array of astronomical objects.  Particularly interesting sources include a bright open cluster of stars and several energetic star-forming regions.  The general red glow is caused by luminous hydrogen gas, while the dark filaments are caused by absorption by dense lanes of dust. The Lagoon Nebula, also known as M8 and NGC 6523, lies about 5000 light-years away.  The Lagoon Nebula can be located with binoculars in the constellation of Sagittarius spanning a region over three times the diameter of a full Moon.
Mysterious Pluto and Charon (1998-07-08)
Pluto is the only planet in our Solar System remaining unphotographed by a passing spacecraft. Distant Pluto and its moon Charon therefore remain somewhat mysterious.  In addition to direct imaging by the Hubble Space Telescope, careful tracking of brightness changes that occur as each object eclipses the other have allowed astronomers to build up the above black & white surface maps.  These maps depict the face of Pluto (left) that always faces Charon, and the face of Charon that always faces away from Pluto. The rectangular pixels are an artifact of the mapping software. The Pluto-Kuiper Express mission is tentatively planned for launch in 2003 and should encounter Pluto around the year 2012.
Hale-Bopp: The Crowd Pleaser Comet (1998-07-09)
In 1997, the bright comet Hale-Bopp may have become the most viewed comet in history -- visible even to casual skywatchers in light polluted cities around the globe. In this picture, taken by photographer Joe Orman on the evening of May 8, 1997, Hale-Bopp easily competes with near twilight skies and a shining, over-exposed, crescent moon above Mobile, Arizona, USA. Where is Hale-Bopp now? Still visible to telescopic observers in the Southern Hemisphere, the comet is outbound, presently about 537 million miles from the Sun. (Jupiter orbits at about 480 million miles.) The long lead time provided by the early discovery of Hale-Bopp has allowed extensive observing campaigns producing a bonanza of information about this primordial chunk of our Solar System.
NGC 1531/2: Interacting Galaxies (1998-07-10)
This dramatic image of an interacting pair of galaxies was made using the 1.5 meter telescope at the Cerro Tololo Inter-American Observatory near La Serena, Chile. NGC 1531 is the background galaxy with a bright core just above center and NGC 1532 is the foreground spiral galaxy laced with dust lanes. The pair is about 70 million light-years away in the southern constellation Eridanus. These galaxies lie close enough together so that each feels the influence of the other's gravity. The gravitational tug-of-war has triggered star formation in the foreground spiral as evidenced by the young, bright blue star clusters along the edge of the front spiral arm. Though the spiral galaxy in this pair is viewed nearly edge-on, astronomers believe the system is similar to the face-on spiral and companion known as M51, the Whirlpool Galaxy.
M64: The Sleeping Beauty Galaxy (1998-07-11)
The Sleeping Beauty galaxy may appear peaceful at first sight but it is actually tossing and turning. In an unexpected twist, recent observations have shown that the center of this photogenic galaxy is rotating in the opposite direction than the outer regions! Stranger still - there is a middle region where the stars rotate in the opposite direction from the surrounding dust and gas. The fascinating internal motions of M64, also cataloged as NGC 4826, are thought to be the result of a collision between a small galaxy and a large galaxy where the resultant mix has not yet settled down.
Asteroid Gaspra's Best Face (1998-07-12)
Asteroid 951 Gaspra is a huge rock tumbling in space.  Gaspra became one of the best-studied asteroids in 1991 when the spacecraft Galileo flew by. In the above photograph, subtle color variations have been exaggerated to highlight changes in reflectivity, surface structure and composition. Gaspra is about 20 kilometers long and orbits the Sun in the main asteroid belt between Mars and Jupiter.
GRB 980703: A Reassuring Redshift (1998-07-13)
In the old days, just over a year ago, astronomers had little idea of the true distance to  gamma-ray bursts.  Did these enigmatic explosions occur in our outer Galaxy, or in the outer Universe?  Last May, a first telling distance measure was made - GRB 970508 showed an absorption line with a redshift of about 0.8 - indicating that this gamma-ray burst (GRB) was an enormous distance away.  Skeptics, however, are not always convinced by an unrepeated measurement. Since then, though, other tantalizing coincidences have occurred: GRB 971214 occurred unusually near a galaxy with the enormous redshift of 3.4, and GRB 980425 occurred unusually near a peculiar low-redshift supernova.  Skeptics were intrigued. Now, the potentially definitive implications of the above-pictured optical transient might impress even the cautious.  GRB 980703's optical transient shows a well-measured redshift from both an absorption line and an emission line: 0.97. The above negative highlights the uncommon transient source with the label "OT", while letters designate common comparison stars.
At Work on Mars (1998-07-14)
To learn about the history ofMars, just ask the rocks.  Last year, that's exactly what the robot rover Sojourner did.  Sojouner can be seen, above, analyzing a rock nicknamed Moe, trying to discern its past.  One significant discovery of the Mars Pathfinder mission was that of conglomerate rocks, indicating the presence of running water in the past.  Such water, in turn, indicates that Mars was much more like watery Earth in the distant past.  Visible in the foreground of this color-enhanced mosaic is part of the Sagan Memorial Station, while a hill nicknamed one of the "Twin Peaks" is visible about a kilometer in the distance.
Ghost Galaxy NGC 2915 (1998-07-15)
How do you find a nearly invisible galaxy?  Pictured above is the blue compact dwarf (BCD) galaxy NGC 2915. In visible light, shown above in yellow, this galaxy appears to be a normal dwarf galaxy, as indicated by the yellow smudge in the image center.  Yet when imaged in a very specific color, shown in blue, a whole spiral galaxy appears.  This specific color is in the radio band and is preferentially emitted by neutral hydrogen atoms. Much about BCD galaxies remains mysterious, such as how the neutral hydrogen obtained its shape, what drives current star formation, and why there is so much dark matter.  NGC 2915 is located at the relatively nearby distance of 15 million light-years - just outside our Local Group of Galaxies.
X-Ray Triple Jet (1998-07-16)
Recorded on July 7, this animation using X-ray images of the Sun shows an amazing event - three nearly simultaneous jets connected with solar active regions. The two frames were taken several hours apart by the Soft X-ray Telescope on board the orbiting Yohkoh observatory. They have a "negative" color scheme, the darker colors representing more intense X-rays from the corona and active regions on the solar surface. The pictures clearly show two curving jets of X-ray hot plasma appearing above the solar equator and one below. A sharp vertical stripe near the jet above center is a digital blemish while the overall shift of the image is due to solar rotation. As the Sun is now approaching the active part of its 11 year cycle, similar single jets are seen every week or so. But the appearance of these three widely separated jets at once is considered an unlikely coincidence and is fueling current speculations about their origins.
Hyakutake: Stars Through A Comet's Tail (1998-07-17)
Comets are cosmic icebergs. They follow very elongated orbits which carry them from the frozen, remote outer reaches of the Solar System to close encounters with the Sun. Heated by sunlight, they slough off layers of material as gas and dust, forming their characteristic awe-inspiring comas (heads) and tails. In the spring of 1996, Comet Hyakutake inspired Arizona photographers Rick Scott and Joe Orman to take this picture showing faint stars near the constellation Ursa Minor (the Little Dipper) shining through the comet's long, graceful tail. Blown by the solar wind, comet tails generally point away from the Sun.
Rockets and Robert Goddard (1998-07-18)
Robert H. Goddard, one of the founding fathers of modern rocketry, was born in Worcester Massachusetts in 1882. As a 16 year old, Goddard read H.G. Wells' science fiction classic "War Of The Worlds" and dreamed of spaceflight. By 1926 he had designed, built, and launched the world's first liquid fuel rocket. During his career he was ridiculed by the press for suggesting that rockets could be flown to the Moon, but he kept up his experiments in rocketry supported in part by the Smithsonian Institution and championed by Charles Lindbergh. Pictured above in 1937 in the desert near Roswell, New Mexico, Goddard examines a nose cone and parachute from one of his test rockets. Widely recognized as a gifted experimenter and engineering genius, his rockets were many years ahead of their time. He died in 1945 holding over 200 patents in rocket technology. A liquid fuel rocket constructed on principles developed by Goddard landed humans on the Moon in 1969.
Globular Cluster M3 (1998-07-19)
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.
La Nina Watch (1998-07-20)
Goodbye El Niño. Hello La Niña? Scientists are watching to see if an evolving pool of relatively cool water in the mid-Pacific Ocean will develop into a full "La Niña".  Over the past several months, the water temperature in the Equatorial Pacific Ocean has been doing a flip-flop.  From being slightly warmer than normal in the winter, a condition called El Niño, much of this water is now slightly colder than normal, a condition that might develop into a La Niña - with global weather consequences.  Pictured above is a false-color satellite image showing relative temperature in Equatorial Pacific taken earlier this month.  The blue color indicates relatively cool water.  Since little has changed since last month, it is possible that the situation has stabilized.  The last two La Nina years were 1988 and 1995.
Nearby Spiral M33 (1998-07-21)
M33 is a prominent nearby spiral galaxy. Nicknamed the Triangulum,  M33 is one of the larger members of the Local Group of Galaxies.  Two massive spiral galaxies dominate the Local Group: M31 and our Milky Way Galaxy.  M33 is the only other spiral galaxy known in the Local Group.  At 3 million light-years, M33 is the second closest spiral galaxy.  M33 is thought by some to be a satellite galaxy to massive M31.  M33 is close enough to appear twice the angular size of the full moon, when viewed with binoculars.  Globular clusters in M33's halo appear unusual and might be much younger than globular clusters in our Galaxy's halo.
Dark Craters on Ganymede (1998-07-22)
Ganymede has craters within craters within craters.  The old surface of the largest moon in the Solar System shows its age by the large amount of these impact features. The above picture released last week shows two old craters with dark floors located in a relatively bright region known as  Memphis Facula, a region itself thought created by an ancient collision.  The strange dark floors of these craters were themselves created long ago and now house craters of their own.  Crater Chrysor, on the left, spans about 6000 meters, about half that of crater Aleyn on the right. The robot spacecraft Galileo took the above photograph during a flyby of this moon of Jupiter in June 1996.