juliensimon/nasa-apod huggingface dataset:
Valles Marineris: The Grand Canyon of Mars (2003-08-24)

The largest canyon in the Solar System cuts a wide swath across the face of Mars.  Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep.  By comparison, the Earth's Grand Canyon in Arizona, USA is 800 kilometers long, 30 kilometers across, and 1.8 kilometers deep.  The origin of the Valles Marineris remains unknown, although a leading hypothesis holds that it started as a crack billions of years ago as the planet cooled.  Recently, several geologic processes have been identified in the canyon.  The above mosaic was  created from over 100 images of Mars taken by Viking Orbiters in the 1970s.   News: Mars closest in over 50,000 years on Wednesday
The Northern Milky Way (2003-08-25)

Many of the stars in our home Milky Way Galaxy appear together as a dim band on the sky that passes nearly over the Earth's north and south poles.  Pictured above is the part of our Galaxy that passes closest over the north pole.  Placing your cursor over the image will bring up the names of several constellations and bright stars.  The diffuse white Galaxy glow is created by billions of stars, while red patches are large emission nebulas, usually marking areas where bright stars have recently formed.  In the north, all of the lights visible at night and all lights that created this image were emitted within the past few thousand years from within the Milky Way Galaxy -- except one.  On the upper right is a small faint patch designated M31, the Andromeda Galaxy.  M31 is a spiral galaxy similar to our Milky Way but so distant it emits the oldest light distinguishable by the unaided eye -- light that takes over two million years to reach us.

Image credit: Astropix.com
Earth Webcam Catches Mars Rotation (2003-08-26)

Mars won't look this good.  Tonight and over the next few days, when Mars is at its closest approach to Earth in nearly 60,000 years, you might get your best view ever of our planetary neighbor.  Please, though, don't expect to see this much structure, or expect to see Mars rotate so much in so brief a period.  The above 20-frame movie was created from 1000 frames of a backyard webcam that were meticulously aligned, added, and digitally sequenced.   Pictured, Mars appears to rotate in a time-lapse sequence, with each frame separated by 30 minutes of real time.  In reality, one full Martian rotation -- a Martian day -- is only about 40 minutes longer than an Earth day.  For those with access to a small telescope, here is how mars will really look.
Big Mars from Hubble (2003-08-27)

At about 10 am Universal Time today, Mars and Earth will pass closer than in nearly 60,000 years.  Mars, noticeably red, will be the brightest object in the eastern sky just after sunset.  Tonight and through much of this week, many communities around the world are running a public Mars Watch 2003 campaign, where local telescopes will zoom in on the red planet.  Pictured above is an image of Mars taken just last night from the Hubble Space Telescope in orbit around the Earth. This image is the most detailed view of Mars ever taken from Earth. Visible features include the south polar cap in white at the image bottom, circular Huygens crater just to the right of the image center, Hellas Impact Basin - the large light circular feature at the lower right, planet-wide light highlands dominated by many smaller craters and large sweeping dark areas dominated by relatively smooth lowlands.
Mars Rising Behind Elephant Rock (2003-08-28)

Yesterday, at about 10 am Universal Time, Mars and Earth passed closer than in nearly 60,000 years.  Mars, noticeably red, remains the brightest object in the eastern sky just after sunset.  The best views of Mars, however, will continue to be from the robot spacecraft currently orbiting Mars: the Mars Global Surveyor and the Mars Odyssey.  The current pass sparked the launching of four new spacecraft toward Mars, some of which will deploy landers early next year and likely return even more spectacular views of our planetary neighbor.  Pictured above, Mars was photographed rising in the southeast behind Elephant Rock in the Valley of Fire State Park, Nevada, USA.

Image credit: Wally Pacholka (Astropics)
The Mineral Moon (2003-08-29)

ven if the Moon really were made of green cheese it probably wouldn't look this bizarre. Still, this mosaic of 53 images was recorded by the Jupiter-bound Galileo spacecraft as it passed near our own large natural satellite in 1992. The pictures were recorded through three spectral filters and combined in an exaggerated false-color scheme to explore the composition of the lunar surface as changes in mineral content produce subtle color differences in reflected light. Familiar to earthdwellers, the lunar near side is on the left, but the space-based view looks down on the Moon's north pole located in the upper half of the image near the shadow line. Blue to orange shades indicate volcanic lava flows. The dark blue Mare Tranquillitatis at the lower left is richer in titanium bearing minerals than the green and orange maria above it. Near the bottom of the image and to the right of Tranquillitatis is the dark oval-shaped Mare Crisium surrounded by shocking pink colors indicating material of the lunar highlands.
Recycling Cassiopeia A (2003-08-30)

For billions of years, massive stars in our Milky Way Galaxy have lived spectacular lives.  Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After a few million years, the enriched material is blasted back into interstellar space where star formation begins anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle. Light from the explosion which created this supernova remnant was probably first seen in planet Earth's sky just over 300 years ago, although it took that light more than 10,000 years to reach us. In this gorgeous Hubble Space Telescope image of cooling filaments and knots in the Cas A remnant, light from specific elements has been color coded to help astronomers understand the recycling of our galaxy's star stuff. For instance, red regions are dominated by emission from sulfur atoms while blue shades correspond to oxygen.  The area shown is about 10 light-years across.
The View from Everest (2003-08-31)

What would it be like to stand atop the tallest mountain on Earth?  To see a full panoramic vista from there, scroll right.  Visible are snow peaked mountains near and far, tremendous cliffs, distant plateaus, the tops of clouds, and a dark blue sky.  Mt. Everest stands 8.85 kilometers above sea level, roughly the maximum height reached by international airplane flights, but much less than the 300 kilometers achieved by a space shuttle.  Hundreds of people have tried and failed to climb the behemoth by foot, a feat first accomplished successfully in 1953.  About 1000 people have now made it to the summit.  Roddy Mackenzie, who climbed the mountain in 1989, captured the above image. Mt. Everest lies in the Himalayan mountains in the country of Nepal.  In the native language of Nepal, the mountain's name is "Sagarmatha" which means "forehead of the sky."

Image credit: Roddy Mackenzie
A Beautiful Trifid (2003-09-01)

The beautiful Trifid Nebula (aka M20), a photogenic study in cosmic contrasts, lies about 5,000 light-years away toward the nebula rich constellation Sagittarius. A star forming region in the plane of our galaxy, the Trifid alone illustrates three basic types of astronomical nebulae; red emission nebulae dominated by light from hydrogen atoms, blue reflection nebulae produced by dust reflecting starlight, and dark absorption nebulae where dense dust clouds appear in silhouette. The bright emission nebula on the right, separated into three parts by obscuring dust lanes, lends the nebula its popular name. Many details are apparent in this gorgeous high-resolution image of the Trifid. For example, light-year long pillars and jets sculpted by newborn stars - visible here in the upper right-hand corner of the emission nebula - appear in Hubble Space Telescope close-up images of the region.

Image credit: Jim and Janet Castano,
Adam Block, 
NOAO, 
AURA, 
NSF
Contemplating Mars (2003-09-02)

Is that really another world?  Thousands of people the world over lined up last week to see Mars through a telescope as the red planet and Earth passed unusually close together in their orbits around the Sun. Reviews of Mars were mixed, with some people disappointed that Mars still appeared somewhat blurry.  Veteran sky gazers appeared somewhat surprised by the popularity of the phenomenon, as it seemed to many that Mars was not very much brighter than it frequently appears, and the event held little promise for real discovery.  Most observers, though, appeared quietly pleased to take advantage of a unique opportunity and see such an uncommon sight.  Many were awed by the simple enormity of being able to see the face of a completely different world with their own eyes. Pictured above, a youngster peered toward Mars last week at an East Antrim Astronomical Society star party at the Big Collin Picnic Area north of Belfast, Northern Ireland, UK.

Image credit: Mark Stronge
(EAAS)
Galactic Supernova Remnant IC 443 (2003-09-03)

About 8000 years ago, a star in our Galaxy exploded.  Ancient humans might have noticed the supernova as a temporary star, but modern humans can see the expanding shell of gas even today.  Pictured above, part of the shell of IC 443 is seen to be composed of complex filaments, some of which are impacting an existing molecular cloud.  Here emission from shock-excited molecular hydrogen is allowing astronomers to study how fast moving supernova gas affects star formation in the cloud.  Additionally, astronomers theorize that the impact accelerates some particles to velocities near the speed of light.  Supernova remnant IC 443 is also known to shine brightly also in infrared and X-ray light.

Image credit: Jean-Charles Cuillandre
Composite Crab (2003-09-04)

The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this composite image of the inner region of the well-known Crab Nebula. The spectacular picture combines optical data (red) from the Hubble Space Telescope and x-ray images (blue) from the Chandra Observatory, also used in the popular Crab Pulsar movies. Like a cosmic dynamo the pulsar powers the x-ray and optical emission from the nebula, accelerating charged particles and producing the eerie, glowing x-ray jets. Ring-like structures are x-ray emitting regions where the high energy particles slam into the nebular material. The innermost ring is about a light-year across. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar is the collapsed core of a massive star that exploded, while the nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed in the year 1054.
SIRTF Streak (2003-09-05)

Streaking skyward, a Boeing Delta 2-Heavy rocket carries NASA's Space InfraRed Telescope Facility (SIRTF) aloft during the early morning hours of August 25th. The dramatic scene was recorded in a time exposure from the pier in Jetty Park at the northern end of Cocoa Beach, Florida, about 2.5 miles from the Cape Canaveral launch site. SIRTF (sounds like "sir tiff") will explore the distant Universe in infrared light as the fourth and final satellite observatory in NASA's Great Observatories Program. The three other large astrophysics satellites were designed for higher energies in the electromagnetic spectrum, with the Hubble Space Telescope operating near visible wavelengths, the Compton Gamma Ray Observatory instruments sensitive to gamma rays, and the Chandra Observatory detecting cosmic x-rays. SIRTF has been launched into an Earth-trailing solar orbit to reduce its exposure to infrared radiation from our fair planet. Cooled by an on board supply of liquid helium, SIRTF's infrared detectors will operate at near absolute zero temperatures. Presently, SIRTF's systems are undergoing a 90-day check out.

Image credit: Ben Cooper
Jupiter Unpeeled (2003-09-06)

Slice Jupiter from pole to pole, peel back its outer layers of clouds, stretch them onto a flat surface ... and for all your trouble you'd end up with something that looks a lot like this. Scrolling right will reveal the full picture, a color mosaic of Jupiter from the Cassini spacecraft. The mosaic is actually a single frame from a fourteen frame movie constructed from image data recorded by Cassini during its leisurely flyby of the solar system's largest planet in late 2000. The engaging movie approximates Jupiter's cloud motions over 24 jovian rotations. To make it, a series of observations covering Jupiter's complete circumference 60 degrees north and south of the equator were combined in an animated cylindrical projection map of the planet. As in the familiar rectangular-shaped wall maps of the Earth's surface, the relative sizes and shapes of features are correct near the equator but become progressively more distorted approaching the polar regions. In the Cassini movie, which also features guest appearances by moons Io and Europa, the smallest cloud structures visible at the equator are about 600 kilometers across.
The Galactic Center in Infrared (2003-09-07)

The center of our Galaxy is a busy place. In visible light, much of the  Galactic Center is obscured by opaque dust.  In infrared light, however, dust glows more and obscures less, allowing nearly one million stars to be recorded in the above photograph.  The Galactic Center itself appears on the right and is located about 30,000 light years away towards the constellation of Sagittarius.  The Galactic Plane of our Milky Way Galaxy, the plane in which the Sun orbits, is identifiable by the dark diagonal dust lane.  The absorbing dust grains are created in the atmospheres of cool red-giant stars and grow in molecular clouds.  The region directly surrounding the Galactic Center glows brightly in radio and high-energy radiation, and is thought to house a large black hole.
Stars and Dust of the Lagoon Nebula (2003-09-08)

The large majestic Lagoon Nebula is home for many young stars and hot gas.  Spanning 100 light years across while lying only about 5000 light years distant, the Lagoon Nebulae is so big and bright that it can be seen without a telescope toward the constellation of Sagittarius.  Many bright stars are visible from NGC 6530, an open cluster that formed in the nebula only several million years ago. The greater nebula, also known as M8 and NGC 6523, is named "Lagoon" for the band of dust seen to the left of the open cluster's center.  A bright knot of gas and dust in the nebula's center is known as the Hourglass Nebula.  The above picture is a digitally sharpened composite of exposures taken in specific colors of light emitted by sulfur (red), hydrogen (green), and oxygen (blue). Star formation continues in the Lagoon Nebula as witnessed by the many globules that exist there.

Image credit: Richard Crisp
A Gemini Sky (2003-09-09)

Where will Gemini take us tonight? It is dusk and Gemini North, one of the largest telescopes on planet Earth, prepares to peer into the distant universe.  Gemini's flexible 8.1-mirror has taken already effectively taken humanity to distant stars, nebulas, galaxies, and quasars, telling us about the geometry, composition, and evolution of our universe. The above picture is actually a composite of over 40 images taken while the Gemini dome rotated, later adding an image of the star field taken from the same location. The Gemini dome is not transparent -- it only appears so because it rotated during the exposures of this image. The constellations of Scorpius and Sagittarius can be seen above the dome, as well as the sweeping band of our Milky Way Galaxy, including the direction toward the Galactic center. Gemini North's twin, Gemini South, resides in Cerro Pachn, Chile.  This night, 2003 August 19, Gemini North took us only into the outer Solar System, observing Pluto in an effort to better determine the composition of its thin atmosphere.
Aurora Over Clouds (2003-09-10)

Aurorae usually occur high above the clouds.  The auroral glow is created when fast-moving charged particles from the Earth's magnetosphere impact air molecules high in the Earth's atmosphere.  An oxygen molecule, for example, will emit a green light when reacquiring an electron lost during a collision.  The lowest part of an aurora will typically occur at 100 kilometers and up, while most clouds usually exist only below about 10 kilometers.  The relative heights of clouds and auroras are shown clearly in the above picture taken last month from near Quebec City, Canada. The most likely time to see an aurora is around midnight.

Image credit: Dominic Cantin
NGC 3370: A Sharper View (2003-09-11)

Similar in size and grand design to our own Milky Way, spiral galaxy NGC 3370 lies about 100 million light-years away toward the constellation Leo. Recorded here in exquisite detail by the Hubble Space Telescope's Advanced Camera for Surveys, the big, beautiful face-on spiral does steal the show, but the sharp image also reveals an impressive array of background galaxies in the field, strewn across the more distant Universe. Looking within NGC 3370, the image data has proved sharp enough to study individual pulsating stars known as Cepheids which can be used to accurately determine this galaxy's distance. NGC 3370 was chosen for this study because in 1994 the spiral galaxy was also home to a well studied stellar explosion -- a type Ia supernova. Combining the known distance to this standard candle supernova, based on the Cepheid measurements, with observations of supernovae at even greater distances, can reveal the size and expansion rate of the Universe itself.
A Note on the Perseus Cluster (2003-09-12)

A truly enormous collection of thousands of galaxies, the Perseus Cluster - like other large galaxy clusters - is filled with hot, x-ray emitting gas. The x-ray hot gas (not the individual galaxies) appears in the left panel above, a false color image from the Chandra Observatory. The bright central source flanked by two dark cavities is the cluster's supermassive black hole. At right, the panel shows the x-ray image data specially processed to enhance contrasts and reveals a strikingly regular pattern of pressure waves rippling through the hot gas.  In other words, sound waves, likely generated by bursts of activity from the black hole, are ringing through the Perseus Galaxy Cluster. Astronomers infer that these previously unknown sound waves are a source of energy which keeps the cluster gas so hot. So what note is the Perseus Cluster playing? Estimates of the distance between the wave peaks and sound speed in the cluster gas suggests the cosmic note is about 57 octaves below B-flat above middle C.
NGC 3132: The Eight Burst Nebula (2003-09-13)

It's the dim star, not the bright one, near the center of NGC 3132 that created this odd but beautiful planetary nebula.  Nicknamed the Eight-Burst Nebula and the Southern Ring Nebula, the glowing gas originated in the outer layers of a star like our Sun.  In this representative color picture, the hot blue pool of light seen surrounding this  binary system is energized by the hot surface of the faint star.  Although photographed to explore unusual symmetries, it's the asymmetries that help make this planetary nebula so intriguing.  Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes running across NGC 3132 are well understood.
The Crab Nebula from VLT (2003-09-14)

The Crab Nebula, filled with mysterious filaments, is the result of a star that was seen to explode in 1054 AD.  This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers.  The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture taken recently from a Very Large Telescope, the color indicates what is happening to the electrons in differentparts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while blue indicates the electrons are whirling around the magnetic field of the inner nebula.  In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.
Globular Cluster M3 (2003-09-15)

This huge ball of stars predates our Sun.  Long before humankind evolved, before dinosaurs roamed, and even before our Earth existed, ancient globs of stars condensed and orbited a young Milky Way Galaxy.  Of the 200 or so globular clusters that survive today, M3 is one of the largest and brightest, easily visible in the Northern hemisphere with binoculars.  M3 contains about half a million stars, most of which are old and red.  Light takes about 100,000 years to reach us from M3, which spans about 150 light years.  The above picture is a composite of blue and red images.

Image credit: S. Kafka
Hurricane Isabel Approaches (2003-09-16)

Where will Hurricane Isabel go?  One of the stronger storm systems of modern times appears headed for one the more populated seaboards on planet Earth -- the east coast of the USA.  Hurricane Isabel, pictured yesteday as it passed east of the Bahamas, has flirted with category 5 status, the most powerful hurricane category. Hurricanes are huge swirling storms with cloud systems typically larger than a state.  Tropical cyclones, called hurricanes in Earth's Western Hemisphere and typhoons in the Eastern Hemisphere, get their immense energy from warm evaporated ocean water.  As this water vapor cools and condenses, it heats the air, lowers pressure and hence causes cooler air to come swooshing in.  Winds can reach over 250 kilometers per hour and become very dangerous.  Much remains unknown about cyclones, including how they are formed and the exact path they will take.
The 2MASS Galaxy Sky (2003-09-17)

Are the nearest galaxies distributed randomly? A plot of over one million of the brightest "extended sources" detected by the Two Micron All Sky Survey (2MASS) shows that they are not.  The vast majority of these infrared extended sources are galaxies.  Visible above is an incredible tapestry of structure that provides limits on how the universe formed and evolved.  Many galaxies are gravitationally bound together to form clusters, which themselves are loosely bound into superclusters, which in turn are sometimes seen to align over even larger scale structures.  In contrast, very bright stars inside our own Milky Way Galaxy cause the vertical blue sash.

Image credit: 2MASS, 
T. H. Jarrett, J. Carpenter, & R. Hurt
Saturn by Three (2003-09-18)

These three views of Saturn were recorded by the Hubble Space Telescope on March 7th of this year, as the southern hemisphere of the solar system's most gorgeous planet reached its maximum 27 degree tilt toward Earth. The images used to construct the false-color pictures were made through a combination of filters covering the electromagnetic spectrum from ultraviolet (top), to visible (middle) and infrared (bottom) wavelengths highlighting different features in the Saturnian atmospheric bands and rings. Well known for its bright ring system and large, mysterious moon Titan, gas giant Saturn is also a planet with a dynamic atmosphere and high-speed winds. In fact, in the 1980s, Voyager spacecraft measured equatorial winds of over 1,000 miles per hour. Giant storm systems, comparable in size to planet Earth itself, have been seen erupting in Saturn's cloud tops.