juliensimon/nasa-apod huggingface dataset:
M51: Cosmic Whirlpool (2006-11-11)

Follow the handle of the Big Dipper away from the dipper's bowl, until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (right), NGC 5195. The pair are about 31 million light-years distant and officially lie within the boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy in small, earthbound telescopes, this sharpest ever picture of M51 was made in January 2005 with the Advanced Camera for Surveys on board the Hubble Space Telescope.
The Cat's Eye Nebula (2006-11-12)

Three thousand light-years away, a dying star throws off shells of glowing gas.  This image from the Hubble Space Telescope reveals the Cat's Eye Nebula to be one of the most complex planetary nebulae known.  In fact, the features seen in the Cat's Eye are so complex that astronomers suspect the bright central object may actually be a binary star system. The term planetary nebula, used to describe this general class of objects, is misleading. Although these objects may appear round and planet-like in small telescopes, high resolution images reveal them to be stars surrounded by cocoons of gas blown off in the late stages of stellar evolution.
A Hurricane Over the South Pole of Saturn (2006-11-13)

What's happening at the south pole of Saturn?  To find out, scientists sent the robot Cassini probe now orbiting Saturn directly over the lower spin axis of the ringed giant.  Cassini found there a spectacular massive swirling storm system with a well developed eye-wall, similar to a hurricane here on Earth.  One image of the storm is shown above, while several frames from the overpass have been made into a movie that shows the huge vortex rotating. The storm is slightly larger than the entire Earth and carries winds that reach 550 kilometers per hour, twice the velocity of a Category 5 hurricane. This pole vortex on Saturn might have been raging for billions of years and is not expected to drift off the pole.
Mercury's Transit: An Unusual Spot on the Sun (2006-11-14)

What's that dot on the Sun? If you look closely, it is almost perfectly round.  The dot is the result of an unusual type of solar eclipse that occurred last week.  Usually it is the Earth's Moon that eclipses the Sun.  Last week, for the first time in over three years, the planet Mercury took a turn.  Like the approach to New Moon before a solar eclipse, the phase of Mercury became a continually thinner crescent as the planet progressed toward an alignment with the Sun.  Eventually the phase of Mercury dropped to zero and the dark spot of Mercury crossed our parent star.  The situation could technically be labeled a Mercurian annular eclipse with an extraordinarily large ring of fire.  From above the cratered planes of the night side of Mercury, the Earth appeared in its fullest phase.  Hours later, as Mercury continued in its orbit, a slight crescent phase appeared again.  The next Mercurian solar eclipse will occur in 2016.

Image credit: David Cortner
A Fog Bow Over California (2006-11-15)

Is that white arch real?  What is being seen is a fogbow, a reflection of sunlight by water drops similar to a rainbow but without the colors.  The fog itself is not confined to an arch -- the fog is mostly transparent but relatively uniform.  The fogbow shape is created by those drops with the best angle to divert sunlight to the observer.  The fogbow's relative lack of colors are caused by the relatively smaller water drops.  The drops active above are so small that the quantum mechanical wavelength of light becomes important and smears out colors that would be created by larger rainbow water drops acting like small prisms reflecting sunlight.  The above striking image of a fogbow was taken last week with the Sun behind the photographer.  Close inspection of the far right of the full image will show one of the two suspension towers of the Golden Gate Bridge in California, USA.

Image credit: Mila Zinkova
Children of the Sun (2006-11-16)

For a moment, planets Jupiter, Venus, Mars, and Mercury all posed near their parent star in this Sun-centered view, recorded on November 11. The picture, from a coronograph onboard the space-based SOlar Heliospheric Observatory, spans 15 degrees with the Sun's size and position indicated by the white circle. Background stars are also visible as the otherwise overwhelming sunlight is blocked by the coronograph's occulting disk. But the planets themselves, in particular Jupiter and Venus, are still bright enough to cause significant horizontal streaks in the image. Mercury is actually moving most rapidly (left to right) through the field and days earlier was seen to cross in front of the solar disk. So what's that bright double star to the left of Mars? Zubenelgenubi, of course.
Hand Drawn Transit (2006-11-17)

The sight of Mercury's tiny round disk drifting slowly across the face of the Sun inspired and entertained many denizens of planet Earth last week. In fact, artist and astronomer Mark Seibold viewed both the 1999 and 2006 transits of the solar system's innermost planet through solar filtered telescopes and composed this rendering of Mercury "hovering in the photosphere" near the edge of an enormous solar disk. The original work is a 23 by 17 inch pastel sketch. While the artist's hand is creatively superimposed, Seibold concentrated on offering an impression of Mercury's silhouette, surrounded by shadings reflecting his visual experience that are not easily captured in photographic exposures. Of course, before the age of cameras drawings were more widely used to record telescopic observations of sunspots and planetary transits.

Image credit: Mark Seibold
Leonids and Leica (2006-11-18)

This lovely view from northern Spain at Cape Creus on the easternmost point of the Iberian peninsula, looks out across the Mediteranean and up into the stream of the 2002 Leonid meteor shower. The picture is a composite of thirty separate one minute exposures taken through a fisheye lens. Over 70 leonid meteors are visible, some seen nearly head on. Bright Jupiter is positioned just to the right of the shower's radiant in Leo. Perched on the moonlit rocks at the bottom right, Leica, the photographers' dog, seems to be watching the on going celestial display and adds a surreal visual element to the scene. The 2006 Leonid meteor shower will be much less intense than in 2002, but will be near its predicted peak this weekend. Sky watchers will have their best view under dark skies in early morning hours with Leo rising above the eastern horizon.

Image credit: Juan
Carlos Casado and Isabel Graboleda
The Car, the Hole, and the Peekskill Meteorite (2006-11-19)

The Peekskill meteor of 1992 was captured on 16 independent videos and then struck a car.  Documented as brighter than the full Moon, the spectacular fireball crossed parts of several US states during its 40 seconds of glory before landing in  Peekskill, New York.  The resulting meteorite, pictured here, is composed of dense rock and has the size and mass of an extremely heavy bowling ball.  If you are lucky enough to find a meteorite just after impact, do not pick it up -- parts of it are likely to be either very hot or very cold.  In this weekend's Leonid meteor shower, few meteors, if any, are expected to hit the ground.

Image credit: Pierre Thomas (LST),
ENS Lyon
M42: Wisps of the Orion Nebula (2006-11-20)

The Great Nebula in Orion, an immense, nearby starbirth region, is probably the most famous of all astronomical nebulas.  Here, glowing gas surrounds hot young stars at the edge of an  immense interstellar molecular cloud only 1500 light-years away.  In the above deep image, faint wisps and sheets of dust and gas are particularly evident.  The Great Nebula in Orion can be found with the unaided eye just below and to the left of the easily identifiable belt of three stars in the popular constellation Orion.  In addition to housing a bright open cluster of stars known as the Trapezium, the Orion Nebula contains many stellar nurseries.   These nurseries contain hydrogen gas, hot young stars, proplyds, and stellar jets spewing material at high speeds.  Also known as M42, the Orion Nebula spans about 40 light years and is located in the same spiral arm of our Galaxy as the Sun.

Image credit: Jon Christensen
A Leonid Meteor Over Sweden (2006-11-21)

This past weekend, small remnant bits of a distant comet lit up the skies over much of planet Earth.  Incoming reports, however, have this year's Leonid meteor shower as less active than Leonid meteor showers a few years ago.  Nevertheless, some sky enthusiasts reported peak meteor bursts as high as one visual meteor per minute.  The parent body of the Leonids meteor shower, Comet Tempel-Tuttle, leaves a trail of expelled sand-size particles every 33 years when it returns to the inner Solar System.  When the Earth passes through a stream of these Sun-orbiting particles, a meteor shower results.   Pictured above, a Leonid meteor was captured two days ago during the early morning hours of November 19 over Vallentuna, Sweden. Although activity levels in meteor showers are notoriously hard to predict, some astronomers speculate that Aurigids meteor shower next September might be unusually rich in bright meteors.

Image credit: P-M Hed�n
A Bucket-Wheel Excavator on Earth (2006-11-22)

Please wait while one of the largest mobile machines in the world crosses the road.  The machine pictured above is a bucket-wheel excavator used in modern surface mining.  Machines like this have given humanity the ability to mine minerals and change the face of planet Earth in new and dramatic ways.  Some open pit mines, for example, are visible from orbit.   The largest excavators are over 200 meters long and 100 meters high, now dwarfing the huge NASA Crawler that transports space shuttles to the launch pads.   Bucket-wheel excavators can dig a hole the length of a football field to over 25 meters deep in a single day. They may take a while to cross a road, though, with a top speed under one kilometer per hour.
Hydrogen in M33 (2006-11-23)

Gorgeous spiral galaxy M33 seems to have more than its fair share of hydrogen. Its inner 30,000 light-years are shown here in an image processed to fully reveal the reddish glow of ionized hydrogen regions (HII regions) sprawling along loose spiral arms that wind toward the galaxy's core. Historically of great interest to astronomers, M33's giant HII regions are some of the largest known stellar nurseries - sites of the formation of short-lived but very massive stars. Intense ultraviolet radiation from the luminous, massive stars ionizes the surrounding hydrogen gas and ultimately produces the characteristic red glow. A prominent member of the local group of galaxies, M33 is also known as the Triangulum Galaxy and lies about 3 million light-years distant.

Image credit: Chris
Schur
Alpha Cam: Runaway Star (2006-11-24)

Runaway stars are massive stars traveling rapidly through interstellar space. Like a ship plowing through cosmic seas, runaway star Alpha Cam has produced this graceful arcing bow wave or bow shock - moving at over 60 kilometers per second and compressing the interstellar material in its path. The bright star above and left of center in this wide (3x2 degree) view, Alpha Cam is about 25-30 times as massive as the Sun, 5 times hotter (30,000 kelvins), and over 500,000 times brighter. About 4,000 light-years away in the long-necked constellation Camelopardalis, the star also produces a strong wind. The bow shock stands off about 10 light-years from the star itself. What set this star in motion? Astronomers have long thought that Alpha Cam was flung out of a nearby cluster of young hot stars due to gravitational interactions with other cluster members or perhaps by the supernova explosion of a massive companion star.

Image credit: Steve Mandel
(Galaxy Images)
3D Mercury Transit (2006-11-25)

Mercury is now visible shortly before dawn, the brightest "star" just above the eastern horizon. But almost two weeks ago Mercury actually crossed the face of the Sun for the second time in the 21st century. Viewed with red/blue glasses, this stereo anaglyph combines space-based images of the Sun and innermost planet in a just-for-fun 3D presentation of the Mercury transit. The solar disk image is from Hinode. (sounds like "hee-no-day", means sunrise). A sun-staring observatory, Hinode was launched from Uchinoura Space Center and viewed the transit from Earth orbit. Superimposed on Mercury's dark silhouette is a detailed image of the planet's rugged surface based on data from the Mariner 10 probe that flew by Mercury in 1974 and 1975.

Image credit: Greg Piepol
M31: The Andromeda Galaxy (2006-11-26)

Andromeda is the nearest major galaxy to our own Milky Way Galaxy.  Our Galaxy is thought to look much like Andromeda.  Together these two galaxies dominate the Local Group of galaxies.  The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it.  The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object.  Andromeda is frequently referred to as M31 since it is the 31st object on  Messier's list of diffuse sky objects.  M31 is so distant it takes about two million years for light to reach us from there.  Although visible without aid, the above image of M31 is a digital mosaic of 20 frames taken with a small telescope.  Much about M31 remains unknown, including how the center acquired two nuclei.

Image credit: Robert Gendler (robgendlerastropixs.com)
Mysterious Spokes in Saturn's Rings (2006-11-27)

What causes the mysterious spokes in Saturn's rings?  Visible on the left of the above image as ghostlike impressions, spokes were first discovered by the Voyager spacecraft that buzzed by Saturn in the early 1980s.  Their existence was unexpected, and no genesis hypothesis has ever become accepted.  Oddly, the spokes were conspicuously absent from initial images sent back by the robot Cassini spacecraft now orbiting Saturn.  Analyses of archived Voyager images have led to the conclusions that the transient spokes, which may form and dissipate over a few hours, are composed of electrically charged sheets of small dust-sized particles. Some recent images from Cassini like that shown above have now finally shown the enigmatic spokes superposed on Saturn's B ring.   Hypotheses for spoke creation include small meteors impacting the rings and electron beams from Saturnian atmospheric lightning spraying the rings.  Observations of the puzzling spokes, as well as creative origin speculations, are ongoing.
Unusual Starburst Galaxy  NGC 1313 (2006-11-28)

Why is this galaxy so discombobulated?  Usually, galaxies this topsy-turvy result from a recent collision with a neighboring galaxy. Spiral galaxy NGC 1313, however, appears to be alone.  Brightly lit with new and blue massive stars, star formation appears so rampant in NGC 1313 that it has been labeled a starburst galaxy.  Strange features of NGC 1313 include that its spiral arms are lopsided and its rotational axis is not at the center of the nuclear bar.  Pictured above, NGC 1313 spans about 50,000 light years and lies only about 15 million light years away toward the constellation of Reticulum. Continued numerical modeling of galaxies like NGC 1313 might shed some light on its unusual nature.
A Big Dish at the VLA Radio Observatory (2006-11-29)

They are so large, they are almost unreal.  The radio dishes of the Very Large Array (VLA) of radio telescopes might appear to some as a strange combination of a dinosaur skeleton and common satellite-TV receiving dish.  Together, the 27 dishes of the VLA combine high sensitivity with high resolution, enabling a series of important astronomical discoveries, including water ice on planet Mercury, micro-quasars in our Galaxy, gravitationally-induced Einstein rings around distant galaxies, and radio counterparts to cosmologically distant gamma-ray bursts. Pictured above, a dish from the VLA was photographed last week near Socorro, New Mexico, USA.

Image credit: Victor Bobbett
A Pelican in the Swan (2006-11-30)

The Pelican Nebula lies about 2,000 light-years away in the high flying constellation Cygnus, the Swan. Also known as IC 5070, this cosmic pelican is appropriately found just off the "east coast" of the North America Nebula (NGC 7000), another surprisingly familiar looking emission nebula in Cygnus. The Pelican and North America nebulae are part of the same large and complex star forming region, almost as nearby as the better-known Orion Nebula. From our vantage point, dark dust clouds (upper left) help define the Pelican's eye and long bill, while a bright front of ionized gas suggests the curved shape of the head and neck. Based on digitized black and white images from the Samuel Oschin Telescope at Palomar Observatory, this striking synthesized color view includes two bright foreground stars and spans about 30 light-years at the estimated distance of the Pelican Nebula.
In the Arms of NGC 1097 (2006-12-01)

A smaller companion seems wrapped in the spiral arms of enigmatic galaxy NGC 1097. This amazingly deep image of the peculiar spiral system, also known as Arp 77, actually combines data from two telescopes, one in the northern and one in the southern hemisphere of planet Earth. The faint details revealed include hints of a mysterious jet emerging toward the top of the view. Seen to be about 42,000 light-years from the larger galaxy's center, the companion galaxy is gravitationally interacting with the spiral and will ultimately merge with it.  NGC 1097's center also harbors a massive black hole. NGC 1097 is located about 45 million light-years away in the chemical constellation Fornax.
Star Trails at 19,000 Feet (2006-12-02)

In myth, Atlas holds up the heavens, but in this stunning view a mountain appears to serve as the southern night sky pivots around a snowy peak. Recorded during a climbing expedition at an altitude above 19,000 feet (temperature -18 degrees C), the picture places the South Celestial Pole over the Andes mountain Ojos del Salado. Topping out at over 22,000 feet, the Ojos del Salado is a stratovolcano, the highest active volcano on planet Earth. The time exposure lasted for an hour, recording the graceful arcing star trails along with the rising Milky Way (left) and setting Magellanic clouds.

Image credit: Serge Brunier
Phobos: Doomed Moon of Mars (2006-12-03)

This moon is doomed.  Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These martian moons may well be captured asteroids originating in the main asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of the Solar System. The larger moon, Phobos, is indeed seen to be a cratered, asteroid-like object in this stunning color image from the Mars Express spacecraft, recorded at a resolution of about seven meters per pixel. But Phobos orbits so close to Mars - about 5,800 kilometers above the surface compared to 400,000 kilometers for our Moon - that gravitational tidal forces are dragging it down. In 100 million years or so it will likely crash into the surface or be shattered by stress caused by the relentless tidal forces, the debris forming a ring around Mars.
Movie: The Active Sun (2006-12-04)

Plumes of hot gas shoot across the surface on even an average day on the Sun.   Such volatile activity was captured in dramatic detail recently by the new Hinode satellite launched by Japan in late September.   Near the horizon, active regions around a sunspot eject hot plasma along the magnetic field lines that connect the sunspot to surrounding regions in the solar atmosphere.  Bright regions are hotter and more active.  The bubbling granularity and continuous activity of the Sun's photosphere is visible in the foreground.   This frame  from the movie is in representative color and covers a solar region of about 8,000 kilometers. (Note: To download the full MPG movie file, click on the picture.)
The Antikythera Mechanism (2006-12-05)

What is it?  It was found at the bottom of the sea aboard an ancient Greek ship.  Its seeming complexity has prompted decades of study, although many of its functions remained unknown.  Recent X-rays of the device have now confirmed the nature of the Antikythera mechanism, and discovered several surprising functions.  The Antikythera mechanism has been discovered to be a mechanical computer of an accuracy thought impossible in 80 BC, when the ship that carried it sunk.   Such sophisticated technology was not thought to be developed by humanity for another 1,000 years. Its wheels and gears create a portable orrery of the sky that predicted star and planet locations as well as lunar and solar eclipses. The Antikythera mechanism, shown above, is 33 centimeters high and similar in size to a large book.

Image credit: Wikipedia
Spirit Rover on Mars Imaged from Orbit (2006-12-06)

If you have the right equipment, you can see the Spirit rover currently rolling across Mars.  The right equipment, however, is currently limited to the High Resolution Imaging Science Experiment onboard the Mars Reconnaissance Orbiter (MRO).  MRO arrived at Mars in March and just started science observations of the red planet last month.   Visible in the above spectacularly high resolution image is the Spirit rover in the Columbia Hills of Mars.  Objects as small as one meter are resolved.   Also visible are the tracks made by the robot explorer and a large plateau of layered rock dubbed Home Plate.   MRO will continue to image the red planet in unprecedented detail, creating images that will likely be important in better understanding the geology and weather on Mars, as well as indicating good candidate landing sites for future missions to Mars.
The Outskirts of M77 (2006-12-07)

Face-on spiral galaxy M77 lies a mere 60 million light-years away toward the aquatic constellation Cetus. Also known as NGC 1068, its very bright core is well studied by astronomers exploring the mysteries of supermassive black holes in active galaxies. While M77 is also seen at x-ray, ultraviolet, infrared, and radio wavelengths, this visible light image highlights another remarkable aspect of the galaxy. In the picture, the data has been enhanced to show outer faint details, following spiral arms and structures that reach far beyond the galaxy's brighter central regions. Including the fainter outskirts, the galaxy's diameter is well over 100 thousand light-years at M77's estimated distance, making it larger than our own spiral Milky Way.

Image credit: Ken Crawford  
(Rancho Del Sol Observatory)
NGC 2174: Emission Nebula in Orion (2006-12-08)

A lesser known sight in the nebula-rich constellation Orion, NGC 2174 can be found with binoculars near the head of the celestial hunter. About 6,400 light-years distant, the glowing cosmic cloud surrounds loose clusters of young stars. Covering an area larger than the full Moon on the sky, this stunning narrow band image adopts a typical color mapping of the atomic emission from NGC 2174. The false-color mapping shows otherwise red hydrogen emission in green hues and emphasizes sulfur emission in red and oxygen in blue. Placing your cursor on the image will reveal an alternative image of the nebula made through broad band filters. The broad band image combines filters in a closer analogy to human vision, dominated by the red glow of hydrogen.

Image credit: Dan Kowall
(Photonhunter.com)