juliensimon/nasa-apod huggingface dataset:
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.

Image credit: Fred Calvert
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.

Image credit: CNES
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.

Image credit: Stefan Seip
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.

Image credit: highest communications tower
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.

Image credit: Top: John Chumack /
Bottom: Juergen Wolf
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.

Image credit: Juan Carlos Casado
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).

Image credit: Canada-France-Hawaii Telescope
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.

Image credit: Scaled Composites
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.

Image credit: C. Smith
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.

Image credit: Marc-André Besel
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.
The Averted Side Of The Moon (2004-10-09)

This vintage 60-kopek stamp celebrates a dramatic achievement. On the 7th of October, 1959 (7/X/1959), the Soviet interplanetary station which has come to be called "Luna 3" successfully photographed the far side of the moon giving denizens of planet Earth their first ever view of this hidden hemisphere. Lacking the digital image technology familiar now, Luna 3 took the pictures on 35mm film which was automatically developed on board. The pictures were then scanned and the signal transmitted to Earth days later in what was perhaps also the first interplanetary fax. In all, seventeen pictures were received providing enough coverage and resolution to construct a far side map and identify a few major features. Depicted on the stamp are regions dubbed the Sea of Moscow, the Soviet Mountains, the Bay of Astronauts, and the Sea of Dreams.
Sunspot Loops in Ultraviolet (2004-10-10)

It was a quiet day on the Sun.  The above image shows, however, that even during off days the Sun's surface is a busy place.  Shown in ultraviolet light, the relatively cool dark regions have temperatures of thousands of degrees Celsius.  Large sunspot group AR 9169 is visible as the bright area near the horizon.  The bright glowing gas flowing around the sunspots has a temperature of over one million degrees Celsius.  The reason for the high temperatures is unknown but thought to be related to the rapidly changing magnetic field loops that channel solar plasma.  Sunspot group AR 9169 moved across the Sun during 2000 September and decayed in a few weeks.
Mosaic of Endurance Crater on Mars (2004-10-11)

Where should this Martian rover explore next?  Possible choices for the Opportunity rover team on Earth in early August were to send the Martian robot inside Endurance crater toward the arc-shaped sand dunes on the left, the unusually shaped rock on the right slope dubbed Wopmay, and lower parts of Burns Cliff at the top of the craters inner slopes.   The Opportunity rover team on Earth chose 1-meter diameter rock Wopmay as their next target, and closer photographs are already being returned.  Below center of the above mosaic is an area already explored by the rover.  Opportunity has recently found rocks in Endurance crater with a network of cracks potentially indicative of dried mud, bolstering the case that Mars had a wet ancient past.
M3: Inconstant Star Cluster (2004-10-12)

Star clusters appear constant because photographs of them are frozen in time.  In reality, though, cluster stars swarm the center and frequently fluctuate in brightness.  Although the time it takes for stars to cross a cluster is about 100,000 years, the time it takes for a star to fluctuate noticeably can be less than one night.  In fact, the above time lapse movie of bright globular cluster M3 was taken over a single night.  Most of the variable stars visible above are RR Lyrae stars, stars that can quickly double their brightness while becoming noticeably bluer.  Furthermore, RR Lyrae stars vary their light in a distinctive pattern that allows unique identification.  Lastly, since RR Lyrae stars all have the same intrinsic brightness, identifying them and measuring how dim they appear tells how far they are, since faintness means farness.  These distances, in turn, help calibrate the scale of the entire universe.

Image credit: J. Hartman & 
K. Stanek 
(Harvard CfA)
Contrail Clutter over Georgia (2004-10-13)

Artificial clouds made by humans may become so common they change the Earth's climate.  The long thin cloud streaks that dominate the above satellite photograph of Georgia are contrails, cirrus clouds created by airplanes.  The  exhaust of an airplane engine can create a contrail by saturating the surrounding air with extra moisture. The wings of a plane can similarly create contrails by dropping the temperature and causing small ice-crystals to form.  Contrails have become more than an oddity - they may be significantly increasing the cloudiness of Earth, reflecting sunlight back into space by day, and heat radiation back to Earth even at night.  The effect on climate is a topic of much research.  You can help NASA measure the actual abundance of contrails by participating in a contrail counting exercise that runs over the next two days.
Glimpse of a Globular Star Cluster (2004-10-14)

Not a glimpse of this cluster of stars can be seen in the inset visible light image (lower right). Still, the infrared view from the Spitzer Space Telescope reveals a massive globular star cluster of about 300,000 suns in an apparently empty region of sky in the constellation Aquila. When astronomers used infrared cameras to peer through obscuring dust in the plane of our Milky Way galaxy, they were rewarded with the surprise discovery of the star cluster, likely one of the last such star clusters to be found. Globular star clusters normally roam the halo of the Milky Way, ancient relics of our galaxy's formative years. Yet the Spitzer image shows this otherwise hidden cluster crossing through the middle of the galactic plane some 10,000 light-years away. At that distance, the picture spans only about 20 light-years. In the false color infrared image, the red streak is a dust cloud which seems to lie behind the cluster core.
Night MAGIC (2004-10-15)

Is it magic? On a rare foggy night, mysterious laser beams seem to play across the MAGIC telescope at Roque de los Muchachos on the Canary Island of La Palma. The lasers are actually part of a system designed to automatically adjust the focusing of the innovative, seventeen meter wide, multi-mirrored instrument. The MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescope itself is intended to detect gamma rays - photons with over 100 billion times the energy of visible light. As the gamma rays impact the upper atmosphere they produce air showers of high-energy particles. The MAGIC camera records in detail the brief flashes of optical light, called Cherenkov light, created by the air shower particles that ultimately correspond to cosmic sources of extreme gamma-rays. While the MAGIC I telescope became operational this year, the dramatic picture shows the nearly completed version of the instrument in October 2003.
The Bubbling Cauldron of NGC 3079 (2004-10-16)

dge-on spiral galaxy NGC 3079 is a mere 50 million light-years away toward the constellation Ursa Major. Shown in this stunning false-color Hubble Space Telescope image, the galaxy's disk - composed of spectacular star clusters in winding spiral arms and dramatic dark lanes of dust - spans some 70,000 light-years. Still, NGC 3079's most eye-catching features are the pillars of gas which tower above a swirling cosmic cauldron of activity at the galaxy's center. Seen in the close-up inset at lower right, the pillars rise to a height of about 2,000 light-years and seem to lie on the surface of an immense bubble rising from the galactic core. Measurements indicate that the gaseous pillars are streaming away from the core at 6 million kilometers per hour. What makes this galaxy's cauldron bubble? Astronomers are exploring the possibility that the superbubble is formed by winds from massive stars. If so, these massive stars were likely born all at once as the galactic center underwent a sudden burst of star formation.
IC 418: The Spirograph Nebula (2004-10-17)

What is creating the strange texture of IC 418?  Dubbed the Spirograph Nebula for its resemblance to drawings from a cyclical drawing tool, planetary nebula IC 418 shows patterns that are not well understood.  Perhaps they are related to chaotic winds from the variable central star, which changes brightness unpredictably in just a few hours.  By contrast, evidence indicates that only a few million years ago, IC 418 was probably a well-understood star similar to our Sun.  Only a few thousand years ago, IC 418 was probably a common red giant star.  Since running out of nuclear fuel, though, the outer envelope has begun expanding outward leaving a hot remnant core destined to become a white-dwarf star, visible in the image center.  The light from the central core excites surrounding atoms in the  nebula causing them to glow.  IC 418 lies about 2000 light-years away and spans 0.3 light-years across.  This false-color image taken from the Hubble Space Telescope reveals the unusual details.