omnianasa/nasa-apod-metadata huggingface dataset:
Mercury: A Cratered Inferno (2004-09-12)
Mercury's surface looks similar to our Moon's.  Each is heavily cratered and made of rock.  Mercury's diameter is about 4800 km, while the Moon's is slightly less at about 3500 km (compared with about 12,700 km for the Earth).  But Mercury is unique in many ways.  Mercury is the closest planet to the Sun, orbiting at about 1/3 the radius of the Earth's orbit.  As Mercury slowly rotates, its surface temperature varies from an unbearably cold -180 degrees Celsius to an unbearably hot 400 degrees Celsius.  The place nearest the Sun in Mercury's orbit changes slightly each orbit - a fact used by Albert Einstein to help verify the correctness of his then newly discovered theory of gravity: General Relativity.   The above picture was taken by the only spacecraft ever to pass Mercury: Mariner 10 in 1974. A new mission, Messenger, launched for Mercury last month and is scheduled to enter orbit around the Solar System's innermost planet in in 2011.
Identify this Phenomenon (2004-09-13)
What caused this ring of colors?  At the time of this writing, MIT Physics Professor Walter Lewin had yet to find someone who can give the correct explanation.  Not students.  Not colleagues.  Not APOD editors.  He wonders how the astute readers of APOD will do.  Can you match wits with Professor Lewin?  Lewin took the above picture in a construction area in Massachusetts on June 20.  Your answer should be able to explain the color sequence and the bright area in the center.  Shortly after he gives the explanation on December 7 during a lecture in his course Vibrations and Waves at MIT, APOD will carry a link to it.  A discussion page for this image will be held in the APOD Forum on the Asterisk*.  Additionally, Professor Lewin will answer appropriate e-mail questions and guesses sent to asklewin@space.mit.edu.
Genesis Mission's Hard Impact (2004-09-14)
A flying saucer from outer space crash-landed in the Utah desert last week after being tracked by radar and chased by helicopters.  No space aliens were involved, however.  The saucer, pictured above, was the Genesis sample return capsule, part of a human-made robot Genesis spaceship launched three years ago by NASA itself to study the Sun.  The unexpectedly hard landing at over 300 kilometers per hour occurred because the parachutes did not open as planned.  The Genesis mission had been orbiting the Sun collecting solar wind particles that are usually deflected away by Earth's magnetic field.  A big question remains -- are the returned samples in good enough condition to recover information about the real composition of the Sun?  Genesis team scientists and engineers are working hard to find out.
Above the Eye of Hurricane Ivan (2004-09-15)
Ninety percent of the houses on Grenada were damaged.  Such is the destructive force of Hurricane Ivan, already one of the most powerful and destructive hurricanes on record.  And the storm will likely make landfall in southern USA tomorrow.  Ivan is the currently the third - and largest - hurricane set to strike the US this hurricane season.  The swirling eye of Hurricane Ivan was photographed above from the orbiting International Space Station (ISS) on Saturday as the storm's sustained 200 kilometer per hour winds wreaked havoc in the Caribbean.  The bad news is that hurricane season in the Atlantic typically lasts until November 30, still over two months away.  The more immediate bad news is that tropical storm Jeanne is next in line coming across the mid-Atlantic Ocean and could pass Puerto Rico sometime today.
Microquasar in Motion (2004-09-16)
Microquasars, bizarre binary star systems generating high-energy radiation and blasting out jets of particles at nearly the speed of light, live in our Milky Way galaxy. The energetic microquasar systems seem to consist of a very compact object, either a neutron star or a black hole, formed in a supernova explosion but still co-orbiting with an otherwise normal star. Using a very long array of radio telescopes, astronomers are reporting that at least one microquasar, LSI +61 303, can be traced back to its probable birthplace -- within a cluster of young stars in the constellation Cassiopeia. About 7,500 light-years from Earth, the star cluster and surrounding nebulosity, IC 1805, are shown in the deep sky image above. The cluster stars are identified by yellow boxes and circles. A yellow arrow indicates the common apparent motion of the cluster stars, the green arrow shows the deduced sky motion of the microquasar system, and the red arrow depicts the microquasar's motion relative to the star cluster itself. Seen nearly 130 light-years from the cluster it once called home, a powerful kick from the original supernova explosion likely set this microquasar in motion.
IC 1805: Light from the Heart (2004-09-17)
Sprawling across hundreds of light-years, emission nebula IC 1805 is a mix of glowing interstellar gas and dark dust clouds. Only about 7,500 light-years away, stars were born in this region whose nickname - the Heart Nebula - derives from its suggestive shape (seen here sideways). This gorgeous, deep telescopic image of the nebula is very colorful, but if you could travel there and gaze across these cosmic clouds with your own eyes, are those the colors you would really see? The short answer is no, even though the image was made with light visible to the human eye. Light from this and other glowing gas clouds surrounding hot, young stars comes in very narrow bands of emission characteristic of energized atoms within the clouds. In fact, the nebular glow is often dominated by hydrogen atoms emitting light in only a small fraction of that broad region of the spectrum that we see as the color red. Adopting an artificial color scheme commonly used for narrow band images of emission nebulae, this beautifully detailed view shows the light from sulfur atoms in red hues, with hydrogen in green, and oxygen atoms in blue.
M55: Globular Star Cluster (2004-09-18)
The fifty-fifth entry in Charles Messier's catalog, M55 is a large and lovely globular cluster of around 100,000 stars. Only 20,000 light-years away in the constellation Sagittarius, M55 appears to earth-bound observers to be nearly 2/3 the size of the full moon. Globular star clusters like M55 roam the halo of our Milky Way Galaxy as gravitationally bound populations of stars known to be much older than stellar groups found in the galactic disk. Astronomers who make detailed studies of globular cluster stars can accurately measure the cluster ages and distances. Their results ultimately constrain the age of the Universe (... it must be older than the stars in it! ), and provide a fundamental rung on the astronomical distance ladder. This stunning three-color image made with astronomical (BVI) filters spans about 100 light-years across the globular cluster M55.
Earth's North Magnetic Pole (2004-09-19)
A magnetic compass does not point toward the true North Pole of the Earth.  Rather, it more closely points toward the North Magnetic Pole of the Earth.  The North Magnetic Pole is currently located in northern Canada.  It wanders in an elliptical path each day, and moves, on the average, more than forty meters northward each day.  Evidence indicates that the North Magnetic Pole has wandered over much of the Earth's surface in the 4.5 billion years since the Earth formed.  The Earth's magnetic field is created by Earth's partially ionized outer core, which rotates more rapidly than the Earth's surface.  Indicated in the above picture is Ellef Ringnes Island, the location of Earth's North Magnetic Pole in 1994.
Seeing Through Saturn's C-Ring (2004-09-20)
Are Saturn's rings transparent?  The Cassini spacecraft that recently entered orbit around Saturn has confirmed that some of Saturn's rings are more transparent than others.  Pictured above, Saturn's main A, B, and C rings can be seen, top to bottom, superposed against the gas giant planet.  Although the B-ring across the top is opaque, Saturn's cloud tops can be clearly seen through the lower C-ring.  The translucent nature of the C-ring likely indicates that it is less densely populated with ring particles than the B-ring.  The above image was taken on July 30 while Cassini was over 7 million kilometers from Saturn.
M24: A Sagittarius Starscape (2004-09-21)
Many vast star fields in the  plane of our Milky Way Galaxy are rich in clouds of dust, and gas.  First and foremost, visible in the above picture are millions of stars, many of which are similar to our Sun.  Next huge filaments of dark interstellar dust run across the image and block the light from millions of more stars yet further across our Galaxy.  The bright red region on the left is part of the Omega Nebula, an emission nebula of mostly hot hydrogen gas also known as M17.  A small bright grouping of stars near the image center is the open cluster M18, while the long bright streak of stars just right of center is M24.  On the far right of the image is the picturesque red emission nebula IC 1283 flanked by two blue  reflection nebulas NGC 6589 and NGC 6590.  These objects are visible with a small telescope toward the constellation of Sagittarius.
Spirit Rover at Engineering Flats on Mars (2004-09-22)
Is it art?  Here the paintbrush was the Spirit robotic rover, the canvas was the soil on Mars, and the artists were the scientists and engineers of the Mars Exploration Rover Mission.  The picture created was mostly unintentional -- the MERS team was primarily instructing Spirit to investigate rocks in and around Hank's Hollow in a location called Engineering Flats on Mars.  After creating the ground display with its treads, the Spirit rover was instructed to photograph the area along with itself in silhouette.  Both Mars rovers, Spirit and Opportunity, are now back in contact after an expected radio blackout caused by Mars moving behind the Sun.  NASA has also announced that it is extending the rovers missions for six months, so long as they keep working.   Today: Day and night have equal duration
La Silla's Starry Night (2004-09-23)
On clear, moonless nights, the stars still come out with a vengance above the high-altitude La Silla astronomical observatory. Taking advantage of a recent visit to this first European Southern Observatory (ESO) site constructed on a mountain top in Chile, ESO software engineer Nico Housen recorded this stunning sky view. Difficult to see from light polluted areas, faint stars and dark dust clouds along the plane of our Milky Way Galaxy arc across the gorgeous photo. In the foreground lies the highly polished 15-meter diameter dish antenna of the Swedish-ESO Submillimeter Telescope (now decommissioned). Beyond it, silhouetted by starlight, is the dome of one of La Silla's large optical instruments, a 3.6 meter telescope. Dramatically reflected in the focusing, mirror-like surface of the dish, the vista behind the photographer appears inverted, with the dark horizon hanging above the Milky Way and the starry night.
Fornax Cluster in Motion (2004-09-24)
Reminiscent of popular images of the lovely Pleiades star cluster that lies within our own Milky Way Galaxy, this false-color x-ray view actually explores the center of a much more extended cosmic family -- the Fornax cluster of galaxies some 65 million light-years away. Spanning nearly 900,000 light-years, the Chandra Observatory composite image reveals high-energy emission from several giant galaxies near the Fornax cluster center and an immense, diffuse cloud of x-ray emitting hot gas. On the whole, the hot cluster gas seems to be trailing toward the upper left in this view. As a result, astronomers surmise that the Fornax cluster core is moving toward the lower right, encountering an intergalactic headwind as it sweeps through a larger, less dense cloud of material. In fact, along with another visible galaxy grouping at the outskirts of the cluster, the Fornax cluster core galaxies seem to be moving toward a common point, attracted by the dominating gravity of unseen structures of dark matter in the region.
The Iron Sun (2004-09-25)
The ultraviolet light emitted by eleven times ionized iron at temperatures over 2 million degrees Farenheit was used to record the above picture of the Sun on September 22, 2001, the date of that year's autumnal equinox. The image was made by the EIT camera onboard the SOHO spacecraft, a space observatory which can continuously observe the Sun. Eleven times ionized iron is atomic iron with eleven of its electrons stripped away. Here the electrons are stripped by the frantic collisions with other atoms and electrons which occur at the extreme temperatures in the Solar Corona. Since electrons are negatively charged, the resulting ionized iron atom is highly positively charged. Astronomer's "shorthand" for eleven times ionized iron is written "Fe XII", the chemical symbol for iron followed by a Roman numeral 12 (Fe I is neutral iron).
Looking Back at an Eclipsed Earth (2004-09-26)
Here is what the Earth looks like during a solar eclipse.  The shadow of the Moon can be seen darkening part of Earth.  This shadow moved across the Earth at nearly 2000 kilometers per hour.  Only observers near the center of the dark circle see a total solar eclipse - others see a partial eclipse where only part of the Sun appears blocked by the Moon.  This spectacular picture of the 1999 August 11 solar eclipse was one of the last ever taken from the Mir space station, which was deorbited in a controlled re-entry in 2001.
The Great Nebula in Orion (2004-09-27)
The Great Nebula in Orion is a colorful place.  Visible to the unaided eye, it appears as a small fuzzy patch in the constellation of Orion.  Long exposure, digitally sharpened images like this, however, show the Orion Nebula to be a busy neighborhood of young stars, hot gas, and dark dust.  The power behind much of the Orion Nebula (M42) is the Trapezium - four of the brightest stars in the nebula.  Many of the filamentary structures visible are actually shock waves - fronts where fast moving material encounters slow moving gas.  The Orion Nebula spans about 40 light years and is located about 1500 light years away in the same spiral arm of our Galaxy as the Sun.
Aurora Over a Communications Tower (2004-09-28)
Higher than highest communications tower, higher than highest mountain, higher than highest airplane, lies the realm of the aurora.  Auroras rarely reach below 60 kilometers, and can range up to 1000 kilometers.  Aurora light results from energetic electrons and protons striking molecules in the Earth's atmosphere.  Frequently, when viewed from space, a complete aurora will appear as a circle around one of the Earth's magnetic poles.  Pictured above is a particularly rare purple auroral corona that occurred on August 30, high above Harstad, Norway.
HUDF: Dawn of the Galaxies (2004-09-29)
When did galaxies form?  Faint red smudges identified on the deepest optical sky image ever taken may well be members of the first class of galaxies.  Detailed inspection of the Hubble Ultra Deep Field (HUDF), taken by the Advanced Camera for Surveys on the Hubble Space Telescope, found the galaxies, circled above, and used their distance and abundance to probe the universe when it was only a few percent of its present age.  Analyses indicate that the discovered class of galaxies is exclusively composed of these smaller dwarf galaxies from which larger modern galaxies must have formed.  Some large modern galaxies make a colorful foreground to the above HUDF.  The first class of dwarf galaxies likely contained energetic stars emitting light that transformed much of the remaining normal matter in the universe from a cold gas to a hot ionized plasma.
Crater Wall on Solis Planum (2004-09-30)
This dramatic perspective view looks south-east along the wall of a large eroded impact crater on Solis Planum, bordering the mountainous Thaumasia region of Mars. Stretching for about 50 kilometers into the scene, the crater wall is around 800 meters high. Located just south and west of the Red Planet's grand Valles Marineris, this area features mountains and fault lines that are seen as evidence of surface plate motions or plate tectonics. The process of plate tectonics has long been shaping the surface of planet Earth but is thought to have been only briefly active on Mars. The image was constructed using color image data from the High Resolution Stereo Camera onboard ESA's Mars Express spacecraft.
Earth Nears Asteroid Toutatis (2004-10-01)
On Wednesday, September 29, the Earth came within one million miles of the asteroid Toutatis -- the closest predicted aproach of our fair planet to a sizable asteroid or comet in this century. Coming within one million miles or about 4 times the Earth-Moon distance, Earth would appear to be nearly the size of the full moon in the asteroid's sky, as suggested in this illustration. In Earth's sky, Toutatis appeared only as a faint object rapidly 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, 3 miles long, and is tumbling through space. Studies of Toutatis and other Earth-crossing asteroids help reveal connections between the Solar System's meteorites, main-belt asteroids and comets. These asteroids also offer tantalizing targets for robotic exploration and, over time, represent potential collision hazards for planet Earth!
Toutatis Nears Planet Earth (2004-10-02)
On Wednesday, September 29, asteroid Toutatis came within one million miles of Earth -- the closest predicted aproach of a sizable asteroid or comet to our fair planet in this century. Coming within one million miles or about 4 times the Earth-Moon distance, Earth would have appeared to be nearly the size of the full moon in the asteroid's sky. In Earth's sky, Toutatis appeared only as a faint, starlike, but rapidly moving object. Even so, asteroid 4179 Toutatis was still bright enough to see in small telescopes. Astronomers John Chumack, observing near Dayton Ohio, and Juergen Wolf from near Palo Alto, California, offer these composite images showing the progress of the asteroid (seen as a series of dots) against a background of distant stars. Their multiple exposures span a two hour period on two different days about a week before the asteroid's record close approach, which tracked through night skies south of the celestial equator.
Comet Hale-Bopp and the North America Nebula (2004-10-03)
Comet Hale-Bopp's 1997 encounter with the inner Solar System allowed many breath-taking pictures.  Above, Comet Hale-Bopp was photographed crossing the constellation of Cygnus, sporting spectacular yellow dust and blue ion tails. Visible on the right in red is the North America Nebula, a bright emission nebula observable from a dark location with binoculars.  The North America Nebula is about 1500 light-years away, much farther than the comet, which was only about 8 light minutes away.  Several bright blue stars from the open cluster M39 are visible just above the comet's blue ion tail.
NGC 6823: Cloud Sculpting Star Cluster (2004-10-04)
Star cluster NGC 6823 is ready for its close-up.  The center of the open cluster, visible on the upper right, formed only about two million years ago and is dominated in brightness by a host of bright young blue stars.  Outer parts of the cluster, visible above in the image center as the stars and pillars of emission nebula NGC 6820, contain even younger stars.  The huge pillars of gas and dust likely get their elongated shape by erosion from hot radiation emitted from the brightest cluster stars.  Striking dark globules of gas and dust are also visible across the bottom of this image by the 25 year old Canada France Hawaii Telescope.  Open star cluster NGC 6823 spans about 50 light years and lies about 6000 light years away toward the constellation of Vulpecula (The Fox).
SpaceShipOne Wins the X-Prize (2004-10-05)
Human space flight has entered the domain of private companies.  Previously, large countries like the US and Russia have hired privately owned civilian companies to do specific tasks in support of their public human space flight programs.  Yesterday, however, the solely corporate SpaceShipOne soared 100 kilometers above the Earth for the second time in two weeks to claim the coveted $10 million dollar X-Prize put forward by Ansari to inspire private space flight development.  The X-prize was modeled after the Orteig prize that was designed to inspire ocean-crossing airplane flights and won by Charles Lindbergh in 1927. The impressive success of SpaceShipOne, designed by a team led by engineer Burt Rutan, could usher in a new age of inexpensive commercial space flights that includes space tourism and an increased presence of humans in space.  Scaled Composite's SpaceShipOne is pictured soaring high above the Earth in a practice run last December.
N11: A Giant Ring of Emission Nebulas (2004-10-06)
How did this unusually large nebula form?  One of the largest nebulas yet detected is actually a complex ring of emission nebulas connected by glowing filaments.  The unusual network, known as N11, spans over 1000 light years and is a prominent structure of the Large Magellanic Cloud, the largest satellite galaxy of our Milky Way Galaxy.  In the center of the above image is open star cluster LH9, also known as NGC 1760, composed of about 50 bright blue stars that emit radiation that has eroded a hole in their surroundings.  A leading hypothesis for the formation of N11 is shells of successive generations of stars being formed further out from the center.  The bright region just above center is N11B, an explosive domain where stars are being formed even today.
Moon Lightning (2004-10-07)
Moonsets are not often quite as exciting as this one. But amateur astronomer Marc-Andre Besel was impressed by the brilliant lighting displays that joined the first quarter Moon and stars of the constellation Scorpius in western skies. On August 22, 2004, his view looked across the Gulf of Mexico from Anna Maria Island, Florida, USA, a region that would experience even more stormy weather in the coming days.  The alluring digital image is a time exposure, by chance capturing the details of a brief flash of lightning along with an overexposed Moon and dramatic cloud formations. In fact, the exposure is long enough to show the background stars as short streaks or trails. The bright yellowish star trail, just above and right of the lightning flash, is red giant star Antares.
Kepler's SNR from Chandra, Hubble, and Spitzer (2004-10-08)
Light from the stellar explosion that created this energized cosmic cloud was first seen on planet Earth in October 1604, a mere four hundred years ago. The supernova produced a bright new star in early 17th century skies within the constellation Ophiuchus. It was studied by astronomer Johannes Kepler and his contemporaries, with out the benefit of a telescope, as they searched for an explanation of the heavenly apparition.  Armed with a modern understanding of stellar evolution, early 21st century astronomers continue to explore the expanding debris cloud, but can now use orbiting space telescopes to survey Kepler's supernova remnant (SNR) across the spectrum. In this tantalizing composite image, x-rays, visible light, and infrared radiation recorded by NASA's astrophysical observatories - the Chandra X-Ray Observatory, Hubble and Spitzer space telescopes - are combined to give a more comprehensive view of the still enigmatic supernova remnant. About 13,000 light years away, Kepler's supernova represents the most recent stellar explosion seen to occur within our Milky Way galaxy.