omnianasa/nasa-apod-metadata huggingface dataset:
An Annular Eclipse of the Sun (1998-08-24)
An annular eclipse of the Sun was visible in parts of the Eastern Hemisphere on Saturday.  The above picture was taken at that time by a video camera in Mersing on the East Coast of Malaysia and emailed to APOD yesterday from an internet cafe in Kuala Lumpur.  An annular solar eclipse will occur when the Moon's angular size is slightly less than the Sun's angular size.  Therefore, when the Moon is directly in front of the Sun, the edges of the Sun are still visible. This solar ring is so bright that the Moon's surface normally appears dark by comparison. The angular sizes of the Sun and Moon change slightly because of the elliptical nature of the Moon's and Earth's orbit. A total solar eclipse would have occurred were the Moon much closer to the Earth.
Moon, Venus, Jupiter, Phoenix (1998-08-25)
Before a relaxing sunrise, the sky begins to glow with unusual delights. Such was the view from Papago Park in Phoenix, Arizona this April.  The glittering objects visible in this photograph are, from lower left to upper right: Phoenix, our Moon, Venus, and Jupiter.  Such proximity is somewhat unusual. Jupiter will be visible in the evening sky through the rest of the year, while Venus can be seen in the early morning sky during the month of September.
The Magellanic Stream (1998-08-26)
Spanning the sky behind the majestic Clouds of Magellan is an unusual stream of gas: the Magellanic Stream.  The origin of this gas might hold a clue to origin and fate of our Milky Way's most famous satellite galaxies: the LMC and the SMC.  Two leading genesis hypotheses have surfaced: that the stream was created by gas stripped off these galaxies as they passed through the halo of our Milky Way, or that the stream was created by the differential gravitational tug of the Milky Way.  Measurements of slight angular motions by the Hipparcos satellite have indicated that the Clouds are leading the Stream.  Now, recent radio measurements have located fresh gas emerging from the Clouds, bolstering the later, tidal explanation.  Most probably, in a few hundred million years, the Magellanic Clouds themselves will fall victim to this same tidal force.
Hercules Galaxies (1998-08-27)
These are galaxies of the Hercules Cluster, an archipelago of "island universes" a mere 650 million light-years distant. This cluster is loaded with gas and dust rich, star forming, spiral galaxies but has relatively few elliptical galaxies, which lack gas and dust and the associated newborn stars. Colors in the composite image show the star forming galaxies with a blue tint and ellipticals with a slightly yellowish cast. In this cosmic vista many galaxies seem to be colliding or merging while others seem distorted - clear evidence that cluster galaxies commonly interact. Over time, the galaxy interactions are likely to affect the the content of the cluster itself. Researchers believe that the Hercules Cluster is significantly similar to young galaxy clusters in the distant, early Universe and that exploring galaxy types and their interactions in nearby Hercules will help unravel the threads of galaxy and cluster evolution.
Hydrogen Trifid (1998-08-28)
Clouds of glowing hydrogen gas mingle with dark dust lanes in the Trifid Nebula, a star forming region in the constellation Sagittarius. In this and other similar emission nebulae, energetic ultraviolet light from an embedded hot young star strips electrons from the surrounding hydrogen atoms. As the electrons and atoms recombine they emit longer wavelength, lower energy light in a well known characteristic pattern of bright spectral lines. At visible wavelengths, the strongest emission line in this pattern is in the red part of the spectrum and is known as "Hydrogen-alpha" or just H-alpha. This image of the nebula was taken using a filter to select only light near the H-alpha wavelength. It shows those regions with substantial emission from atomic hydrogen. The relative strength of this emission can trace the densities of atoms within the gas cloud.
Orion Star Colours (1998-08-29)
What determines a star's colour? Its temperature. Red stars are cool, around 3,000 kelvins (K), while blue stars are hotter and can have temperatures over 30,000 K. Our own lovely yellow Sun's temperature is a comforting 6,000 K. Differences in star colours 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 colours 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.
The Sun Erupts (1998-08-30)
The Sun is a seething ball of extremely hot gas. Above, the Sun was captured by Skylab in 1973 throwing off one the largest eruptive prominences in recorded history. The Sun has survived for about 5 billion years, and will likely survive for another 5 billion. The Sun is not on fire, will never explode, and a solar flare will never destroy the Earth.  The Sun continues to present many unanswered questions. For example: Why is the Sun's corona so hot? What causes the Sun's unusual magnetic field? Why does the Sun's center emit so few neutrinos?
A3827: Galactic Cannibal (1998-08-31)
It was mealtime in galaxy cluster Abell 3827. The hungry cluster dominant galaxy in A3827's center is seen being fed.  Breakfast included five smaller galaxies unfortunate enough to wander too close to the cluster's central supergiant galaxy.  The remnants of these five galaxies can be seen in the center of this false-color picture. A single massive galaxy dominates the centers of many compact clusters of galaxies.  A3827 is so distant, having a redshift of 0.1, that light takes about 1.5 billion years to get here from there.  We are therefore seeing this cluster only as it existed 1.5 billion years ago, so that these five galaxies are probably by now all digested into the huge cluster center.
A Colorful Aurora (1998-09-01)
A solar storm overtook the Earth on August 26th. The Earth survived unscathed, as usual, although many northerners reported an impressive display of aurora.  Many of these auroras changed rapidly, with patterns appearing and disappearing sometimes in less than a second.  Out away from city lights, observers also reported an unusually spectacular array of colors.  Some of these colors were captured in the photograph above.  Solar particles that strike oxygen high in Earth's atmosphere cause rare, red auroras, while oxygen lower to the ground will glow a more familiar green. Ionized nitrogen glows blue or red.
Saturn from Earth (1998-09-02)
Saturn is the second largest planet in our Solar System. Saturn has been easily visible in the sky since history has been recorded.  Galileo used one of the first telescopes in 1610 to discover Saturn's rings, which he first thought were moons.  Maxwell showed in 1856 that Saturn's rings couldn't be a single solid, since Saturn's own gravity would break it up.  Were Saturn's rings assembled into a single body, it would measure less than 100 kilometers across.  The origin of Saturn's rings, and of unusual radial patterns that appear on them called spokes, are still unknown. The above representative-color picture was taken from Earth in infrared light. A robot spacecraft Cassini launched in 1997 will reach Saturn in 2004.
SGR 1900+14: Magnetar (1998-09-03)
On August 27th an intense flash of X-rays and gamma-rays swept through our Solar System. Five spacecraft of the Third InterPlanetary gamma-ray burst Network, Ulysses, WIND, RXTE, NEAR, and BeppoSAX, recorded the high energy signal -- a signal so strong that it saturated detectors on WIND and RXTE and triggered the safety mode automatic shut-off of the NEAR gamma-ray instrument! As plotted here, the count rate for the Ulysses detector abruptly spiked to a high level and then slowly tailed off showing smaller peaks roughly every 5 seconds. The signal and location provided by these spacecraft observations leads researchers to identify the source as a dramatic flare-up from one of only four previously known "Soft Gamma Repeaters" . These exotic sources of gamma-rays are believed to be highly magnetized spinning neutron stars called Magnetars. Imaginatively cataloged as SGR 1900+14, this magnetar is estimated to have been born in a supernova explosion about 1,500 years ago and to have a magnetic field 500,000,000,000,000 times stronger than Earth's.
Nozomi: Earth and Moon (1998-09-04)
Japan launched its first mission to orbit Mars, Nozomi (Hope), on July 3rd from the Kagoshima Space Center on the island of Kyushu. Nozomi's goal is to explore the Martian atmosphere and magnetic field as well as regions of the planet's surface and moons. Formerly known as Planet B, the spacecraft will use highly elliptical orbits with successive Earth/Moon flybys to help slingshot itself along its ultimate trajectory toward Mars, arriving at the red planet in October 1999. This stunning picture of the crescent Earth-Moon system was taken by Nozomi's onboard camera on July 18 from a point in space about 100,000 miles from the Earth and 320,000 miles from the Moon. Vibrant and bright, the reflective clouds and oceans of Earth contrast strongly with the dark, somber tones of the lunar surface.
The Pulsar Powered Crab (1998-09-05)
In the Summer of 1054 A.D. Chinese astronomers reported that a star in the constellation of Taurus suddenly became as bright as the full Moon. Fading slowly, it remained visible for over a year. It is now understood that a spectacular supernova explosion - the detonation of a massive star whose remains are now visible as the Crab Nebula- was responsible for the apparition. The core of the star collapsed to form a rotating neutron star or pulsar, one of the most exotic objects known to 20th century astronomy. Like a cosmic lighthouse, the rotating Crab pulsar generates beams of radio, visible, x-ray and gamma-ray energy which, as the name suggests, produce pulses as they sweep across our view. Using a stunning series of visible light images taken with the Hubble Space Telescope (HST), astronomers have discovered spectacular pulsar powered motions within the Crab nebula. Highlights of this HST Crab "movie" show wisps of material moving away from the pulsar at half the speed of light, a scintillating halo, and an intense knot of emission dancing, sprite-like, above the pulsar's pole. Only 6 miles wide but more massive than the sun, the pulsar's energy drives the dynamics and emission of the nebula itself which is more than 10 lightyears across. In this HST image, the pulsar is the left most of the two bright central stars.
Mariner's Mercury (1998-09-06)
Mercury, the closest planet to the Sun, remains the most mysterious of the Solar System's inner planets. Hiding in the Sun's glare it is a difficult target for Earth bound observers. The only spacecraft to explore Mercury close-up was Mariner 10 which executed 3 flybys of Mercury in 1974 and 1975, surveying approximately 45 percent of its surface. Mariner 10 deftly manuevered to photograph part of the sunlit hemisphere during each approach, passed behind the planet, and continued to image the sun-facing side as the spacecraft receded. Its highest resolution photographs recorded features approximately a mile across. A recent reprocessing of the Mariner 10 data has resulted in this dramatic mosaic.  Like the Earth's Moon, Mercury's surface shows the scars of impact cratering - the smooth vertical band and patches visible above represent regions where no image information is available.
The Sky Towards Sagittarius (1998-09-07)
A variety of stars and nebulae can be found towards the constellation of Sagittarius.  Dense fields of stars laced with dark lanes of dust crowd this region only a few degrees from the center of our Galaxy.  Prominent nebulae include the red Lagoon Nebula (M8) in the lower right and the multicolored Trifid Nebula (M20) in the upper right.  Recent high-resolution images of these nebulae show unusual features such as funnel-shaped clouds and proplyds that are not well understood.
A Cluster Too Far (1998-09-08)
Why is this galaxy cluster so red? Nearby clusters have galaxies with colors that are much more yellow and blue.  A leading explanation is that this cluster of galaxies lies so far across our universe (z~1) that cosmological time dilation significantly reddens the light.  If true, this cluster might lie too far away to have formed in a dense universe, implying that our universe is not very dense.  HST 035528+09435 is one of the reddest clusters found in the Hubble Space Telescope's Medium Deep Survey.  Astronomers will now work to confirm the high distance to this cluster, and contemplate what it signifies about the nature of our universe.
Crater Copernicus (1998-09-09)
One of the more prominent craters on the Moon is named Copernicus.  Copernicus is a large young crater visible with binoculars slightly northwest of the center of the Moon's Earth-facing hemisphere.  Copernicus is distinguished by its size and by the many bright rays pointing out from it. Although Copernicus is relatively young for a lunar crater, it was formed nearly a billion years ago by a colossal impact. The center of Copernicus is about 93 kilometers across.  The above picture was taken in 1972 by the last human mission to the moon: Apollo 17.  The prospects for a return have been boosted recently with increased evidence of ice deposits near the lunar poles.
Europa: Ridges and Rafts on a Frozen Moon (1998-09-10)
The large Jovian moon Europa may harbor liquid water beneath its frozen crust. Controversy surrounding this idea has been recently fueled by dramatic images of Europa's surface from the Galileo spacecraft. This alluring color image was produced by combining low resolution color data with higher resolution mosaics recorded during three separate flybys and covers about 120 by 150 miles.  The eerie terrain of grooved linear ridges and crustal plates which seem to have broken apart and rafted into new positions could indicate subsurface water or slush. Blue tints represent relatively old ice surfaces while reddish regions may contain material from more recent internal geological activity. White splotches are bright material blasted from the young impact crater Pwyll located about 600 miles south (to the right) of this area. Many believe that large reservoirs of water hold out the tantalizing possibility of organisms living on this dim, distant world.
Help Map The Moon (1998-09-11)
You can help map the Moon. Early tomorrow morning (Saturday, September 12) the Moon will occult, or pass in front of, the bright star Aldebaran as viewed from some Southern and Eastern areas of the U.S. as well as regions in the Caribbean Sea, Nova Scotia, Newfoundland, Mexico, and Central America. Aldebaran will disappear behind the bright edge of the third quarter moon and reappear behind the darkened edge. Accurately timed home video camera recordings from different locations can be used to make improved maps of the height of the lunar terrain at these occultation points. Interested? Follow the instructions on the International Occultation Timing Association HomePage which detail how to tape a familiar TV channel, take your running camcorder outside to record the occultation, and then return to tape a few more minutes of the TV channel. (First, determine if the occultation will be visible from your location!) You can then donate your tape by mailing it to the address given. Leave yourself plenty of time for a practice run and be sure to check the weather before going to a lot of trouble!  This mosaic mapping the North polar region of the lunar surface was constructed from images recorded by the Galileo spacecraft in 1992.
Star Trails in Northern Skies (1998-09-12)
As the Earth spins on its axis, the sky seems to rotate around us. This motion produces the beautiful concentric trails traced 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.
Galileo Demonstrates the Telescope (1998-09-13)
Galileo Galilei made a good discovery great. Upon hearing at age 40 that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted his own telescope and turned it toward the sky. Galileo quickly discovered that our Moon had craters, that Jupiter had its own moons, that the Sun has spots, and that Venus has phases like our Moon. Galileo, who lived from 1564 to 1642, made many more discoveries.  Galileo claimed that his observations only made sense if all the planets revolved around the Sun, as championed by Aristarchus and Copernicus, not the Earth, as was commonly believed then. The powerful Inquisition made Galileo publicly recant this conclusion, but today we know he was correct.
Dust Hip-Deep on Phobos (1998-09-14)
Landing on the Martian Moon Phobos might be harder than previously thought. The reason: Moon dust.  Recent photographs of Phobos have indicated that a layer of fine powder estimated to be a meter deep covers the whole surface.  Evidence comes from infrared pictures that indicate the rapid speed that Phobos' surface cools after sunset.   The above high-resolution picture of Phobos was taken last month by the Mars Global Surveyor spacecraft now orbiting Mars. The larger of two Martian moons, measures about 20 kilometers across, and orbits so close that Mars' gravity should rip it apart in another 50 million years.
The NTT SUSI Deep Field (1998-09-15)
What happens if you point a large telescope at nothing?  The above New Technology Telescope SUSI Deep Field photograph isolated a small patch of sky picked to contain no bright objects at all.  A very long exposure was then taken, similar to the Hubble Deep Field, in order to see the many faint objects that are usually washed out by the light of bright foreground objects.  What remains is a cosmic wallpaper rich in distant galaxies.  Galaxies as faint as magnitude 26 were found to be irregularly distributed, with several unusual pairings of different colored objects.  This and other deep field images are being released for detailed inspection by anyone interested.  New deep field images are being planned.
Jupiters Rings Revealed (1998-09-16)
Why does Jupiter have rings?  Jupiter's rings were discovered in 1979 by the passing Voyager 1 spacecraft, but their origin has always been a mystery.  Recent data from the Galileo spacecraft currently orbiting Jupiter now confirms that these rings were created by meteoroid impacts on small nearby moons.  As a small meteoroid strikes tiny Adrastea, for example, it will bore into the moon, vaporize, and explode dirt and dust off into a Jovian orbit.  Pictured above is an eclipse of the Sun by Jupiter, as viewed from Galileo. Small dust particles high in Jupiter's atmosphere, as well as the dust particles that compose the rings, can be seen by reflected sunlight.
Radio, The Big Ear, And The Wow! Signal (1998-09-17)
Since the early days of radio and television we have been freely broadcasting signals into space. For some time now, we have been listening too. Ohio State University's radio telescope, affectionately known as "The Big Ear" , was one of the first and largest listeners. Designed by John Kraus, OSU's Big Ear (about the size of three football fields) consisted of an immense metal ground plane with two fence-like reflectors (one fixed and one tiltable) and relied on the Earth's rotation to help scan the sky. This photo, taken by former Big Ear student volunteer Rick Scott, looks out across the ground plane toward the fixed reflector with the "receiver horns" in the foreground. This May, the final pieces of the Big Ear were torn down, but its explorations of the radio universe will be long remembered.  Starting in 1965, the Big Ear was used in an ambitious premier survey of the radio sky, ultimately finding over 20,000 celestial radio sources. Changing its focus in the 1970s, it became the first telescope to continuously listen for signals from extraterrestrial civilizations. For an exciting moment during August 1977 a very strong and unanticipated signal, dubbed the Wow! Signal, was detected by the Big Ear. But alas, heard only once, the cause of the signal could not be determined.
Lunar Prospects (1998-09-18)
Launched on January 6th, NASA's Lunar Prospector spacecraft has been exploring the Moon with instruments designed to sense global properties while orbiting pole-to-pole, 63 miles above the lunar surface. Now over half way through its primary mission, impressive science results include a much-needed precision gravity map of the lunar surface, global maps of elemental composition, the detection of mini-magnetospheres related to large impact sites, and evidence pointing toward a small iron-rich lunar core. But perhaps the most spectacular recent announcement has underscored Prospector's earlier block-buster - the detection of substantial water-ice at both the North and South lunar poles. An analysis of data collected so far is consistent with near-pure water ice deposits - the residue of cometary impacts - buried beneath as much as 18 inches of dry dusty regolith. And the estimates now suggest 10 times more water in each polar region than previously thought! The small Prospector spacecraft carries no cameras for lunar imaging, but the Moon is relatively well photographed. This detailed, color-enhanced nearside mosaic was produced from images taken by the Galileo spacecraft as it passed the Moon in December of 1992.
18 Miles From Deimos (1998-09-19)
Diminutive Deimos is the smallest of the two tiny Moons of Mars. Potato-shaped and barely 6 miles wide this asteroid-like body was visited by the Viking 2 orbiter in 1977. This image was made when the spacecraft approached to within 18 miles of Deimos' surface. One of the most detailed pictures of a celestial body ever taken by an orbiting spacecraft, the field of view is less than a square mile and features just under 10 feet across are visible. Craters and large chunks of rock are seen scattered on the surface while some of the craters appear to be covered by a layer of powdery soil or "regolith".
Isaac Newton Explains the Solar System (1998-09-20)
Sir Isaac Newton changed the world. Born in 1643, Newton was only an above-average student. But he went home from Cambridge one summer in 1665, thought a lot about the physical nature of the world, and came back two years later with a revolutionary understanding of mathematics, gravitation, and optics. A Professor of his, upon understanding what Newton had done, resigned his own position at Cambridge so Newton could have it. Newton's calculus provided a new mathematical framework for the rapid solution of whole classes of physical problems.  Newton's law of gravitation explained in one simple formula how apples fall and planets move.  Newton's insights proved to be so overwhelmingly powerful he was the first scientist ever knighted.
NGC 281: Cluster, Clouds, and Globules (1998-09-21)
NGC 281 is a busy workshop of star formation.  Prominent features include a small open cluster of stars, a diffuse red-glowing emission nebula, large lanes of obscuring gas and dust, and dense knots of dust and gas in which stars may still be forming.  The open cluster of stars IC 1590 visible on the upper right has formed only in the last few million years.  The brightest member of this cluster is actually a multiple-star system shining light that helps ionize the nebula's gas, causing the red glow visible throughout.  The lanes of dust on the lower right might be the home of future star formation.  Particularly striking in the above photograph are the dark Bok globules visible against the bright nebula.  Stars are probably forming there right now. The entire NGC 281 system lies about 10 thousand light years distant.