omnianasa/nasa-apod-metadata huggingface dataset:
The Milky Way Over the French Alps (2002-09-23)
Have you ever seen the band of our Milky Way Galaxy?  Chances are you have never seen it like this -- nor could you.  In a clear sky from a dark location at the right time, a faint band of light is visible across the sky.  This band is the disk of our spiral galaxy.  Since we are inside this disk, the band appears to encircle the Earth.  The above spectacular picture is a bit of a digital trick, though.  A first shot was taken in July 2000 with the camera counter-rotating from the Earth so that the stars appear fixed.  This allowed a long exposure from which a great amount of detail could emerge from the background star field.  Later, after moonrise, a much shorter image was taken from the same location catching details of the French Alps near Mount Blanc, the highest mountain in Western Europe.  Reflections in the water were later enhanced digitally.
To Fly Free in Space (2002-09-24)
What would it be like to fly free over the seas and clouds of Earth?  The first to experience such an "untethered space walk" were NASA astronauts Bruce McCandless and Robert Stewart during Space Shuttle mission 41-B in 1984.  McCandless, pictured above, used a Manned Maneuvering Unit (MMU) to move in and around the cargo bay of the space shuttle.  The MMU works by shooting jets of nitrogen and has since been used to help deploy and retrieve satellites.  With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless in space. The MMU was replaced in 2001 with the SAFER backpack propulsion unit.
Jupiter, Moons and Bees (2002-09-25)
Rising before the Sun on September 4, Jupiter and an old cresent Moon gathered in the dim constellation of Cancer. Watching from a hillside near Austin, Texas, planet Earth, astrophotographer Russell Croman recorded this view of their passing as clouds gracefully dimmed the brilliant moonlight. Earthshine illuminates the lunar night side and on close inspection, bright Jupiter at the lower right appears tightly flanked by its own four large Galilean moons. Next to Jupiter lies a loose swarm of stars just below the clouds. The stars are the brighter members of the nearby star cluster M44, popularly known as the Beehive cluster. Croman's remarkable digital image has been processed only slightly to improve the visibility of the earthshine region and Jupiter's moons.
Rocket Trail at Sunset (2002-09-26)
Bright light from a setting Sun and pale glow from a rising Moon both contribute to this stunning picture of a rocket exhaust trail twisting and drifting in the evening sky. Looking west, the digital telephoto view was recorded from Table Mountain Observatory near Wrightwood California, USA on September 19, four days before the autumnal equinox. The rocket, a Minuteman III solid fuel missile, was far down range when the image was taken. Launched from Vandenberg Air Force Base it carried its test payload thousands of miles out over the Pacific Ocean. The red/orange color from the setting Sun dramatically intensifies near the top of the rocket trail, but below the sunset line, the very bottom of the trail is faintly illuminated from the east by a nearly full Moon.  Still in full sunlight, the bright diffuse cloud at the top of the trail, the result of a rocket stage separation, is tinged with rainbows likely produced by high altitude ice crystals forming in the exhaust plume.  Astronomer James Young comments that the cloud takes on the appearance of a white dove flying from right to left across the sky.
Accretion Disk Simulation (2002-09-27)
Don't be fooled by the familiar symmetry. The graceful spiral structure seen in this computer visualization does not portray winding spiral arms in a distant galaxy of stars. Instead, the graphic shows spiral shock waves in a three dimensional simulation of an accretion disk -- material swirling onto a compact central object that could represent a white dwarf star, neutron star, or black hole. Such accretion disks power bright x-ray sources within our own galaxy. They form in binary star systems which consist of a donor star (not shown above), supplying the accreting material, and a compact object whose strong gravity ultimately draws the material towards its surface. For known x-ray binary systems the size of the accretion disk itself might fall somewhere between the diameter of the Sun (about 1,400,000 kilometers) and the diameter of the Moon's orbit (800,000 kilometers). One interesting result of the virtual reality astrophysics illustrated here is that the simulated disk develops instabilities which tend to smear out the pronounced spiral shocks.
X-Ray Rainbows (2002-09-28)
A drop of water or prism of glass can spread out visible sunlight into a rainbow of colors. In order of increasing energy, the well known spectrum of colors in a rainbow runs red, orange, yellow, green, blue, indigo, violet. X-ray light too can be spread out into a spectrum ordered by energy ... but not by drops of water or glass. Instead, the orbiting Chandra X-ray Observatory uses a set of 540 finely ruled, gold gratings to spread out the x-rays, recording the results with digital detectors. The resulting x-ray spectrum reveals much about the compositions, temperatures, and motions within cosmic x-ray sources. This false color Chandra image shows the x-ray spectrum of a star system in Ursa Major cataloged as XTE J1118+480 and thought to consist of a sun-like star orbiting a black hole. Unlike the familiar appearance of a prism's visible light rainbow, the energies here are ordered along radial lines with the highest energy x-rays near the center and lowest energies near the upper left and lower right edges of the image. The central spiky region itself is created by x-rays from the source which are not spread out by the array of gratings.
Venus: Just Passing By (2002-09-29)
Venus, the second closest planet to the Sun, is a popular way-point for spacecraft headed for the gas giant planets in the outer reaches of the solar system. Why visit Venus first? Using a "gravity assist " maneuver, spacecraft can swing by planets and gain energy during their brief encounter saving fuel for use at the end of their long interplanetary voyage. This colorized image of Venus was recorded by the Jupiter-bound Galileo spacecraft shortly after its gravity assist flyby of Venus in February of 1990. Galileo's glimpse of the veiled planet shows structure in swirling sulfuric acid clouds. The bright area is sunlight glinting off the upper cloud deck. A recent intriguing but controversial hypothesis holds that living microbes might exist in the upper clouds of Venus.
D. rad Bacteria: Candidate Astronauts (2002-09-30)
These bacteria could survive on another planet.  In an Earth lab, Deinococcus radiodurans (D. rad) survive extreme levels of radiation, extreme temperatures, dehydration, and exposure to genotoxic chemicals.  Amazingly, they even have the ability to repair their own DNA, usually with 48 hours.  Known as an extremophile, bacteria such as D. rad are of interest to NASA partly because they might be adaptable to help human astronauts survive on other worlds.  A recent map of D. rad's DNA might allow biologists to augment their survival skills with the ability to produce medicine, clean water, and oxygen.  Already they have been genetically engineered to help clean up spills of toxic mercury.  Likely one of the oldest surviving life forms, D. rad was discovered by accident in the 1950s when scientists investigating food preservation techniques could not easily kill it.  Pictured above, Deinococcus radiodurans grow quietly in a dish.
Rectangular Ridges on Mars (2002-10-01)
What could cause rectangular ridges on Mars?  As data flows in from the two spacecraft currently orbiting Mars, surface structures are seen that are not immediately understood.  These structures pose puzzles that planetary geologists are eager to solve, as they might provide clues to past processes that have shaped Mars over billions of years.  On the right of the above image is an unusual array of ridges first spotted in Mariner 9 data in 1972.  A ridge wall runs for about 5 kilometers.  Two competing progenitor theories include hardened sand dunes and once-molten rock that seeped through surface cracks and cooled.  Dubbed "Inca City" for their resemblance to stone walls of an ancient Earth civilization, the new Mars Global Surveyor images now show them to be part of a larger circular pattern, indicating an origin possibly related to the impact crater.  (Non-natural origin hypotheses are not invoked by conservative scientists unless clear indications exist that natural processes could not work.)
Star Clouds Toward the Southern Crown (2002-10-02)
The flowing trails of dust toward Corona Australis, the constellation of the Southern Crown, are visible here not because they glow, but because they absorb and reflect.  The dust appears bluer when seen near bright stars because it preferentially reflects blue light.  The densest knots of dust are so thick that no background stars or interior stars can be seen through them.  These knots indicate molecular clouds filled with cool gas where future stars will likely form.  The above image spans about 5 degrees while the reflection nebula lies about 500 light-years distant.
V838 Mon: Mystery Star (2002-10-03)
A leading candidate for the most mysterious star found in recent times is variable star V838 Monocerotis. At a distance of about 8,000 light-years, V838 Mon was discovered to be in outburst in January of this year. Initially thought to be a familiar type of classical nova, astronomers quickly realized that instead, V838 Mon may be a totally new addition to the astronomical zoo. Observations indicate that the erupting star transformed itself over a period of months from a small under-luminous star a little hotter than the Sun, to a highly-luminous, cool supergiant star undergoing rapid and complex brightness changes. The transformation defies the conventional understanding of stellar life cycles. A most notable feature of V838 Mon is the "expanding" nebula which now appears to surround it. Seen above in two separate images from the South African Astronomical Observatory's 1 meter telescope, the nebula is probably a light echo from shells of formerly unseen material lost by the star during its previous evolution. Light-years in diameter, the shells progressively reflect the light from V838 Mon's outbursts, providing an opportunity to look back at the history of this remarkable star's behaviour.
Facing NGC 6946 (2002-10-04)
From our vantage point in the Milky Way Galaxy, we see NGC 6946 face on. The big beautiful spiral galaxy is located just 10 million light-years away, behind a veil of foreground stars in the high and far-off constellation of Cepheus. Looking from the bright core outward along the loose, fragmented spiral arms, the galaxy's colors show a striking change from the yellowish light of old stars in the galaxy's center to young blue star clusters and reddish star forming regions. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, during the 20th century, at least six supernovae, the death explosions of massive stars, were discovered in NGC 6946. In this sharp composite color digital image, a small barred structure is just visible at the gorgeous galaxy's core.
X-Ray Cygnus A (2002-10-05)
Amazingly detailed, this false-color x-ray image is centered on the galaxy Cygnus A. Recorded by the orbiting Chandra Observatory, Cygnus A is seen here as a spectacular high energy x-ray source. But it is actually more famous at the low energy end of the electromagnetic spectrum as one of the brightest celestial radio sources. Merely 700 million light-years distant, Cygnus A is the closest powerful radio galaxy and the false-color radio image (inset right) shows remarkable similarity to Chandra's x-ray view. Central in both pictures, the center of Cygnus A shines brightly while emission extends 300,000 light-years to either side along the same axis. Near light speed jets of atomic particles produced by a massive central black hole are believed to cause the emission. In fact, the x-ray image reveals "hot spots" suggestive of the locations where the particle jets are stopped in surrounding cooler, denser gas. The x-ray image also shows that the jets have cleared out a huge cavity in the surrounding gas. Bright swaths of emission within the cavity likely indicate x-ray hot material ... swirling toward the central black hole.
The Lagoon Nebula in Three Colors (2002-10-06)
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.  When viewed by eye, cluster light is dominated by an overall red glow that is caused by luminous hydrogen gas, while the dark filaments are caused by absorption by dense lanes of dust. The above picture, from the Curtis-Schmidt Telescope, however, shows the nebula's emission in three exact colors specifically emitted by hydrogen, oxygen, and sulfur. 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.
The Galaxy and the Quasar (2002-10-07)
Is the galaxy in the center connected to the quasar on the upper right? Disagreements about systems like this have raged for decades and have been used to challenge the foundations of modern cosmology.  Some believe that the quasar Markarian 205 was recently ejected from galaxy NGC 4319, indicating that the high redshift of Markarian 205 is not indicative of its distance.  Most astronomers have come to believe, however, that the two are not physically associated, and that the high redshift of Markarian 205 indeed indicates that it lies across our universe.  In this predominant view, as with a tree branch that happens to point toward the Moon, their juxtaposition in the above image is just coincidence.
The X-Ray Jets of XTE J1550 (2002-10-08)
The motion of ultra-fast jets shooting out from a candidate black hole star system have now been documented by observations from the orbiting Chandra X-ray Observatory.  In 1998, X-ray source XTE J1550-564 underwent a tremendous outburst.  Jets of material sent streaming into space at near light-speed impacted existing gas heating it so much it glowed in X-ray light.  The panels on the left of the above image show in X-rays that the hot spots have moved out by more than three light years in the time since the explosion, with the left jet recently fading below detectability.  The drawing of the right depicts the binary star system that likely produced the X-ray jets, with a normal red star on the left dumping matter into an accretion disk around the black hole on the right.  The jets are thought to be emitted along the spin axis of the black hole.
Quaoar: Large Asteroid in the Outer Solar System (2002-10-09)
Asteroids almost as large as planets are still being discovered in our own Solar System.  Recently an asteroid more than half the size of Pluto was found orbiting at a distance only a little further than the Solar System's most distant planet.   The large asteroid moves relative to background stars in the discovery images shown above taken by the Oschin Telescope at Palomar, California, USA.  Quaoar, the name suggested for the space rock by its discoverers, is one of several large asteroids discovered recently that roam in the distant Kuiper Belt.  Quaoar's size was resolved by images from the Hubble Space Telescope.  Quaoar is likely a  cold world covered in ice from which the Sun appears only as a particularly bright star.
Dusty Environs of Eta Carinae (2002-10-10)
Car is a massive star, but it's not as bright as it used to be. Now only easily visible in binoculars or a small telescope, Eta Carinae has a history of spectacular flaring and fading behavior. In fact, in April of 1843 Eta Car briefly became second only to Sirius as the brightest star in planet Earth's night sky, even though at a distance of about 7,500 light-years, it is about 800 times farther away. Surrounded by a complex and evolving nebula, Eta Carinae is seen near the center of this false-color infrared image, constructed using data from the Midcourse Space Experiment (MSX). The MSX satellite mapped the galactic plane in 1996. In the picture, wispy, convoluted filaments are clouds of dust glowing at infrared wavelengths. Astronomers hypothesize that Eta Car itself will explode as a supernova in the next million years or so. Massive Eta Car has even been considered a candidate for a hypernova explosion and the potential source of a future gamma-ray burst.
Fomalhaut Dust Disk Indicates Planets (2002-10-11)
One of the brightest stars on the sky likely has planets.  Fomalhaut, actually the 17th brightest star in the night sky, is a mere 22 light-years away but only a fraction of the age of our Sun.  Recent observations in far infrared light with a detector cooled to near zero kelvins indicate a dust disk surrounding Fomalhaut that has both a hole in the center and a warped edge.  Now the hole in the center indicates that dust has fallen onto interior planets -- possibly like the Earth -- while the warp at the edge indicates the gravitational pull of a planet like Jupiter or Saturn.  The discovery image was taken with the SCUBA instrument through the James Clerk Maxwell Telescope in Hawaii, USA.  The above illustration shows what the Fomalhaut dusty planetary system might look like from near the large planet.
Chandra Deep Field (2002-10-12)
Officially the Chandra Deep Field - South, this picture represents the deepest ever x-ray image of the Universe. One million seconds of accumulated exposure time with the orbiting Chandra X-ray Observatory went in to its making. Concentrating on a single, otherwise unremarkable patch of sky in the constellation Fornax, this x-ray image corresponds to the visible light Hubble Deep Field - South released in 1998. Chandra's view, color coded with low energies in red, medium in green, and high-energy x-rays in blue, shows many faint sources of relatively high-energy x-rays. These are likely active galaxies feeding supermassive central black holes and large clusters of galaxies at distances of up to 12 billion light-years. The stunning picture supports astronomers' ideas of a youthful universe in which massive black holes were much more dominant than at present.
CG4: A Ruptured Cometary Globule (2002-10-13)
The odd looking "creature" to the right of center in the above photo is a gas cloud known as a cometary globule.  This globule, however, has ruptured.  Cometary globules are typically characterized by dusty heads and elongated tails.  These features cause cometary globules to have visual similarities to comets, but in reality they are very much different.  Globules are frequently the birthplaces of stars, and many show very young stars in their heads. The reason for the rupture in the head of this object is not completely known.  The galaxy to the left of center is very far in the distance and is only placed near CG4 by chance superposition.
IC 5146: The Cocoon Nebula (2002-10-14)
How did this nebula get created?  The Cocoon Nebula, cataloged as IC 5146, is a strikingly beautiful nebula located about 4,000 light years away toward the constellation of Cygnus.  Inside the Cocoon is a newly developing open cluster of stars.  Like other stellar nurseries, the Cocoon Nebula is, at the same time, an emission nebula, a reflection nebula, and an absorption nebula.  Speculation based on recent measurements holds that the massive star in the center of the above image opened a hole in an existing molecular cloud through which much of the glowing material flows.  The same star, which formed about 100,000 years ago, now provides the energy source for much of the emitted and reflected light from this nebula.
Aurora's Ring (2002-10-15)
Gusting solar winds and blasts of charged particles from the Sun made the early days of October rewarding ones for those anticipating auroras. While out enjoying the stormy space weather from Toemmeraas, Norway, Trygve Lindersen recorded this picturesque apparition of the northern lights with a digital camera on October 6. From this perspective, the curtains of green light formed a ring which seemed to hover, wraithlike, just above the foreground trees. But the ring of light was actually 100 kilometers or more above the trees and the greenish glow produced by oxygen molecules interacting with energetic electrons and fluorescing near the edge of space. After days of enchanting auroral displays on planet Earth, the solar activity which triggered October's geomagnetic storms seems to have subsided ... for now.
Oklo: Ancient African Nuclear Reactors (2002-10-16)
The remnants of nuclear reactors nearly two billion years old were found in the 1970s in Africa.  These reactors are thought to have occurred naturally. No natural reactors exist today, as the relative density of fissile uranium has now decayed below that needed for a sustainable reaction.  Pictured above is Fossil Reactor 15, located in Oklo, Gabon.  Uranium oxide remains are visible as the yellowish rock.  Oklo by-products are being used today to probe the stability of the fundamental constants over cosmological time-scales and to develop more effective means for disposing of human-manufactured nuclear waste.
Centaurus A: Young Blue Star Stream (2002-10-17)
Almost lost in this cosmic jumble of stars, gas and dust is a faint but definite blue arc -- a stream of young stars whose formation was probably triggered as a small dwarf galaxy was torn apart approaching the giant elliptical galaxy Centaurus A. The 2,000 light-year long arc is revealed in the upper right corner of this processed color digital image, while the dense central region of Centaurus A is near the bottom. Star clusters that make up the blue arc are likely strung out along the incoming trajectory of the small galaxy and are estimated to be only 200-400 million years old. The remarkable result suggests that astronomers have identified a spectacular example of a kind of galactic cannibalism in progress, a process which is believed to contribute to the formation and evolution of large galaxies, including our own Milky Way. Over time, stars and star clusters in this stream should eventually disperse and merge with tumultuous Centaurus A.  The image data was recorded with the four meter Blanco telescope at Cerro Tololo Inter-American Observatory.
At the Center of the Milky Way (2002-10-18)
At the center of our Milky Way Galaxy lies a black hole with over 2 million times the mass of the Sun. Once a controversial claim, this astounding conclusion is now virtually inescapable and based on observations of stars orbiting very near the galactic center. Using one of the Paranal Observatory's very large telescopes and the sophisticated infrared camera NACO, astronomers patiently followed the orbit of a particular star, designated S2, as it came within about 17 light-hours of the center of the Milky Way (17 light-hours is only about 3 times the radius of Pluto's orbit). Their results convincingly show that S2 is moving under the influence of the enormous gravity of an unseen object which must be extremely compact -- a supermassive black hole. This deep NACO near-infrared image shows the crowded inner 2 light-years of the Milky Way with the exact position of the galactic center indicated by arrows. NACO's ability to track stars so close to the galactic center can accurately measure the black hole's mass and perhaps even provide an unprecedented test of Einstein's theory of gravity as astronomers watch a star orbit a supermassive black hole.