juliensimon/nasa-apod huggingface dataset:
Prometheus and the F Ring (2016-01-08)

In Greek myth Prometheus was a Titan, known for bringing fire from Mount Olympus. But in modern times the name is given to a small moon of Saturn, orbiting just inside Saturn's F ring. In a complex interaction, the tiny potato-shaped moon interacts with the icy ring particles creating structures along the F ring still not fully understood. One of the highest resolution views of Prometheus, this image of its pocked surface posing with the thin F ring in the background was taken during the Cassini spacecraft's close approach on December 6, 2015. Elongated Prometheus is roughly 150 kilometers (90 miles) long by 70 kilometers wide.
Barred Spiral Galaxy NGC 1300 (2016-01-09)

Big, beautiful, barred spiral galaxy NGC 1300 lies some 70 million light-years away on the banks of the constellation Eridanus. This Hubble Space Telescope composite view of the gorgeous island universe is one of the largest Hubble images ever made of a complete galaxy. NGC 1300 spans over 100,000 light-years and the Hubble image reveals striking details of the galaxy's dominant central bar and majestic spiral arms. In fact, on close inspection the nucleus of this classic barred spiral itself shows a remarkable region of spiral structure about 3,000 light-years across. Like other spiral galaxies, including our own Milky Way, NGC 1300 is thought to have a supermassive central black hole.   Free APOD Lecture: Editor to speak tonight in Philadelphia
Sun Storm: A Coronal Mass Ejection (2016-01-10)

What's happening to our Sun?  Another Coronal Mass Ejection (CME)!  The Sun-orbiting SOHO spacecraft has imaged many erupting filaments lifting off the active solar surface and blasting enormous bubbles of magnetic plasma into space. Direct light from the sun is blocked in the inner part of the featured image, taken in 2002, and replaced by a simultaneous image of the Sun in ultraviolet light.  The field of view extends over two million kilometers from the solar surface. While hints of these explosive events, called coronal mass ejections or CMEs, were discovered by spacecraft in the early 70s, this dramatic image is part of a detailed record of this CME's development from the presently operating SOHO spacecraft.  Near the maximum of the solar activity cycle, CMEs now typically occur several times a week.  Strong CMEs may profoundly influence space weather. Those directed toward our planet can have serious effects.   Astrophysicists: Browse 1,100+ codes in the Astrophysics Source Code Library
A Colorful Solar Corona over the Himalayas (2016-01-11)

What are those colorful rings around the Sun?  A corona visible only to Earth observers in the right place at the right time.  Rings like this will sometimes appear when the Sun or Moon is seen through thin clouds.  The effect is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud.  Since light of different colors has different wavelengths, each color diffracts differently. Solar Coronae are one of the few quantum color effects that can be easily seen with the unaided eye. This type of solar corona is a visual effect due to water in Earth's atmosphere and is altogether different from the solar corona that exists continually around the Sun -- and stands out during a total solar eclipse.  In the foreground is the famous Himalayan mountain peak Ama Dablam (Mother's Necklace),   Follow APOD on: Facebook,  Google Plus, or Twitter

Image credit: Jeff Dai
The California Nebula (2016-01-12)

What's California doing in space?  Drifting through the Orion Arm of the spiral Milky Way Galaxy, this cosmic cloud by chance echoes the outline of California on the west coast of the United States. Our own Sun also lies within the Milky Way's Orion Arm, only about 1,500 light-years from the California Nebula. Also known as NGC 1499, the classic emission nebula is around 100 light-years long. On the featured image, the most prominent glow of the California Nebula is the red light characteristic of hydrogen atoms recombining with long lost electrons, stripped away (ionized) by energetic starlight. The star most likely providing the energetic starlight that ionizes much of the nebular gas is the bright, hot, bluish Xi Persei just to the right of the nebula.  A regular target for astrophotographers, the California Nebula can be spotted with a wide-field telescope under a dark sky toward the constellation of Perseus, not far from the Pleiades.

Image credit: Farmakopoulos Antonis
Reflections on the 1970s (2016-01-13)

The 1970s are sometimes ignored by astronomers, like this beautiful grouping of reflection nebulae in Orion - NGC 1977, NGC 1975, and NGC 1973 - usually overlooked in favor of the substantial glow from the nearby stellar nursery better known as the Orion Nebula. Found along Orion's sword just north of the bright Orion Nebula complex, these reflection nebulae are also associated with Orion's giant molecular cloud about 1,500 light-years away, but are dominated by the characteristic blue color of interstellar dust reflecting light from hot young stars. In this sharp color image a portion of the Orion Nebula appears along the bottom border with the cluster of reflection nebulae at picture center. NGC 1977 stretches across the field just below center, separated from NGC 1973 (above right) and NGC 1975 (above left) by dark regions laced with faint red emission from hydrogen atoms. Taken together, the dark regions suggest to many the shape of a running man.

Image credit: Adam Block
Infrared Portrait of the Large Magellanic Cloud (2016-01-14)

Cosmic dust clouds ripple across this infrared portrait of our Milky Way's satellite galaxy, the Large Magellanic Cloud. In fact, the remarkable composite image from the Herschel Space Observatory and the Spitzer Space Telescope show that dust clouds fill this neighboring dwarf galaxy, much like dust along the plane of the Milky Way itself. The dust temperatures tend to trace star forming activity. Spitzer data in blue hues indicate warm dust heated by young stars. Herschel's instruments contributed the image data shown in red and green, revealing dust emission from cooler and intermediate regions where star formation is just beginning or has stopped. Dominated by dust emission, the Large Magellanic Cloud's infrared appearance is different from views in optical images. But this galaxy's well-known Tarantula Nebula still stands out, easily seen here as the brightest region to the left of center. A mere 160,000 light-years distant, the Large Cloud of Magellan is about 30,000 light-years across.
Wright Mons in Color (2016-01-15)

Informally named Wright Mons, a broad mountain about 150 kilometers across and 4 kilometers high with a wide, deep summit depression is featured in this inset image captured during the New Horizons flyby of Pluto in July 2015. Of course, broad mountains with summit craters are found elsewhere in the Solar System, like the large shield volcano Mauna Loa on planet Earth or giant Olympus Mons on Mars. New Horizons scientists note the striking similarity of Pluto's Wright Mons, and nearby Piccard Mons, to large shield volcanoes suggests the two could be giant cryovolcanoes that once erupted molten ice from the interior of the cold, distant world. In fact, found on a frozen dwarf planet Wright Mons could be the largest volcano in the outer Solar System. Since only one impact crater has been identified on its slopes, Wright Mons may well have been active late in Pluto's history. This highest resolution color image also reveals red material sparsely scattered around the region.
The View Toward M106 (2016-01-16)

A big, bright, beautiful spiral, Messier 106 is at the center of this galaxy filled cosmic vista. The two degree wide telescopic field of view looks toward the well-trained constellation Canes Venatici, near the handle of the Big Dipper. Also known as NGC 4258, M106 is about 80,000 light-years across and 23.5 million light-years away, the largest member of the Canes II galaxy group. For a far away galaxy, the distance to M106 is well-known in part because it can be directly measured by tracking this galaxy's remarkable maser, or microwave laser emission. Very rare but naturally occuring, the maser emission is produced by water molecules in molecular clouds orbiting its active galactic nucleus. Another prominent spiral galaxy on the scene, viewed nearly edge-on, is NGC 4217 below and right of M106. The distance to NGC 4217 is much less well-known, estimated to be about 60 million light-years.

Image credit: Fabian Neyer
The Galactic Center in Infrared (2016-01-17)

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 featured photograph.  The Galactic Center itself appears on the left and is located about 30,000 light years away towards the constellation of the Archer (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.   Follow APOD on: Facebook,  Google Plus, or Twitter
Proxima Centauri: The Closest Star (2016-01-18)

Does the closest star to our Sun have planets?  No one is sure -- but you can now follow frequent updates of a new search that is taking place during the first few months of this year. The closest star, Proxima Centauri, is the nearest member of the Alpha Centauri star system.  Light takes only 4.24 years to reach us from Proxima Centauri.  This small red star, captured in the center of the featured image by the Hubble Space Telescope, is so faint that it was only discovered in 1915 and is only visible through a telescope.  Telescope-created X-shaped diffraction spikes surround Proxima Centauri, while several stars further out in our Milky Way Galaxy are visible in the background.  The brightest star in the Alpha Centauri system is quite similar to our Sun, has been known as long as recorded history, and is the third brightest star in the night sky.  The Alpha Centauri system is primarily visible from Earth's Southern Hemisphere.  Starting last week, the European Southern Observatory's Pale Red Dot project began investigating slight changes in Proxima Centauri to see if they result from a planet -- possibly an Earth-sized planet.  Although unlikely, were a modern civilization found living on a planet orbiting Proxima Centauri, its proximity makes it a reasonable possibility that humanity could communicate with them.    #PaleRedDot : Follow the search for planets around Proxima Centauri.
A Dark Sand Dune on Mars (2016-01-19)

What is that dark sand dune doing on Mars? NASA's robotic rover Curiosity has been studying it to find out, making this the first-ever up-close investigation of an active sand dune on another world.  Named Namib Dune, the dark sand mound stands about 4 meters tall and, along with the other Bagnold Dunes, is located on the northwestern flank of Mount Sharp. The featured image was taken last month and horizontally compressed here for comprehensibility.  Wind is causing the dune to advance about one meter a year across the light bedrock underneath, and wind-blown sand is visible on the left. Part of the Curiosity rover itself is visible on the lower right.  Just in the past few days, Curiosity scooped up some of the dark sand for a detailed analysis. After further exploration of the Bagnold Dunes, Curiosity is scheduled to continue its trek up the 5-kilometer tall Mount Sharp, the central peak in the large crater where the car-sized rover landed.
Stars and Globules in the Running Chicken Nebula (2016-01-20)

The eggs from this gigantic chicken may form into stars.  The featured emission nebula, shown in scientifically assigned colors, is cataloged as IC 2944 but known as the Running Chicken Nebula for the shape of its greater appearance.  Seen toward the top of the image are small, dark molecular clouds rich in obscuring cosmic dust. Called Thackeray's Globules for their discoverer, these "eggs" are potential sites for the gravitational condensation of new stars, although their fates are uncertain as they are also being rapidly eroded away by the intense radiation from nearby young stars. Together with patchy glowing gas and complex regions of reflecting dust, these massive and energetic stars form the open cluster Collinder 249. This gorgeous skyscape spans about 60 light-years at the nebula's estimated 6,000 light-year distance.

Image credit: Martin Pugh
The View Toward M101 (2016-01-21)

Sweeping through northern skies, Comet Catalina (C/2013 US10) made its closest approach on January 17, passing about 6 light-minutes from our fair planet. Dust and ion tails clearly separated in this Earth-based view, the comet is also posed for a Messier moment, near the line-of-sight to M101, grand spiral galaxy in Ursa Major. A cosmic pinwheel at the lower left, M101 is nearly twice the size of our own Milky Way galaxy, but some 270 thousand light-centuries away. Both galaxy and comet are relatively bright, easy targets for binocular-equipped skygazers. But Comet Catalina is now outbound from the inner Solar System and will slowly fade in coming months. This telescopic two panel mosaic spans about 5 degrees (10 Full Moons) on the sky.

Image credit: Fritz
Helmut Hemmerich
21st Century M101 (2016-01-22)

One of the last entries in Charles Messier's famous catalog, big, beautiful spiral galaxy M101 is definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way Galaxy. M101 was also one of the original spiral nebulae observed with Lord Rosse's large 19th century telescope, the Leviathan of Parsontown. In contrast, this multiwavelength view of the large island universe is a composite of images recorded by space-based telescopes in the 21st century. Color coded from X-rays to infrared wavelengths (high to low energies), the image data was taken from the Chandra X-ray Observatory (purple), the Galaxy Evolution Explorer ( blue), Hubble Space Telescope(yellow), and the Spitzer Space Telescope(red). While the X-ray data trace the location of multimillion degree gas around M101's exploded stars and neutron star and black hole binary star systems, the lower energy data follow the stars and dust that define M101's grand spiral arms. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 25 million light-years away. (Editor's Note: Original APOD retracted on January 25.)
Big Dipper, Deep Sky (2016-01-23)

The Big Dipper is an easy to recognize, well-known asterism in northern skies, though many see the Plough or Wagon. Famous bright nebulae of the north can also be found along its familiar lines, highlighted in this carefully composed scene with telescopic insets framed in the wider-field skyview. All from Messier's catalog, M101 and M51 are cosmic pinwheel and whirlpool on the left, spiral galaxies far beyond the Milky Way. To the right, M108, a distant edge-on spiral galaxy is seen close to our galaxy's own owl-faced planetary nebula M97. Taken on January 16, the wider-field view seems to include an extra star along the Dipper's handle, though. That's Comet Catalina (C/2013 US10) now sweeping through northern nights.

Image credit: Lorand Fenyes
Star Cluster R136 Bursts Out (2016-01-24)

In the center of star-forming region 30 Doradus lies a huge cluster containing some of the largest, hottest, and most massive stars known. These stars, known collectively as star cluster R136, were captured in the featured image in visible light by the Wide Field Camera 3 in 2009 peering through the Hubble Space Telescope. Gas and dust clouds in 30 Doradus, also known as the Tarantula Nebula, have been sculpted into elongated shapes by powerful winds and ultraviolet radiation from these hot cluster stars.  The 30 Doradus Nebula lies within a neighboring galaxy known as the Large Magellanic Cloud and is located a mere 170,000 light-years away.
Where Your Elements Came From (2016-01-25)

The hydrogen in your body, present in every molecule of water, came from the Big Bang.  There are no other appreciable sources of hydrogen in the universe.  The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen.  Much of the iron in your body was made during supernovas of stars that occurred long ago and far away.  The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts.  Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life.  The featured periodic table is color coded to indicate humanity's best guess as to the nuclear origin of all known elements.  The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research.
A Candidate for the Biggest Boom Yet Seen (2016-01-26)

It is a candidate for the brightest and most powerful explosion ever seen -- what is it?  The flaring spot of light was found by the All Sky Automated Survey for Supernovae (ASASSN) in June of last year and labelled ASASSN-15lh.  Located about three billion light years distant, the source appears tremendously bright for anything so far away: roughly 200 times brighter than an average supernova, and temporarily 20 times brighter than all of the stars in our Milky Way Galaxy combined. Were light emitted by ASASSN-15lh at this rate in all directions at once, it would be the most powerful explosion yet recorded. No known stellar object was thought to create an explosion this powerful, although pushing the theoretical limits for the spin-down of highly-magnetized neutron star -- a magnetar -- gets close.  Assuming the flare fades as expected later this year, astronomers are planning to use telescopes including Hubble to zoom in on the region to gain more clues.  The above-featured artist's illustration depicts a hypothetical night sky of a planet located across the host galaxy from the outburst.
An Airglow Fan from Lake to Sky (2016-01-27)

Why would the sky look like a giant fan? Airglow. The featured intermittent green glow appeared to rise from a lake through the arch of our Milky Way Galaxy, as captured last summer next to Bryce Canyon in Utah, USA.  The unusual pattern was created by atmospheric gravity waves, ripples of alternating air pressure that can grow with height as the air thins, in this case about 90 kilometers up.  Unlike auroras powered by collisions with energetic charged particles and seen at high latitudes, airglow is due to chemiluminescence, the production of light in a chemical reaction.  More typically seen near the horizon, airglow keeps the night sky from ever being completely dark.   Follow APOD on: Facebook,  Google Plus, or Twitter

Image credit: Dave Lane;
 Rollover Annotation:  Judy Schmidt
Elliptical M60, Spiral NGC 4647 (2016-01-28)

Giant elliptical galaxy M60 and spiral galaxy NGC 4647 do look like an odd couple in this sharp cosmic portrait from the Hubble Space Telescope. But they are found in a region of space where galaxies tend to gather, on the eastern side of the nearby Virgo Galaxy Cluster. About 54 million light-years distant, bright M60's simpler egg-like shape is created by its randomly swarming older stars, while NGC 4647's young blue stars, gas and dust are organized into winding arms rotating in a flattened disk. Spiral NGC 4647 is estimated to be more distant than M60, some 63 million light-years away. Also known as Arp 116, the pair of galaxies may be on the verge of a significant gravitational encounter, though. M60 (aka NGC 4649) is about 120,000 light-years across. The smaller NGC 4647 spans around 90,000 light-years, about the size of our own Milky Way.

Image credit: NASA
Hidden Galaxy IC 342 (2016-01-29)

Similar in size to large, bright spiral galaxies in our neighborhood, IC 342 is a mere 10 million light-years distant in the long-necked, northern constellation Camelopardalis. A sprawling island universe, IC 342 would otherwise be a prominent galaxy in our night sky, but it is hidden from clear view and only glimpsed through the veil of stars, gas and dust clouds along the plane of our own Milky Way galaxy. Even though IC 342's light is dimmed by intervening cosmic clouds, this deep telescopic image traces the galaxy's obscuring dust, blue star clusters, and glowing pink star forming regions along spiral arms that wind far from the galaxy's core. IC 342 may have undergone a recent burst of star formation activity and is close enough to have gravitationally influenced the evolution of the local group of galaxies and the Milky Way.

Image credit: Fabiomassimo Castelluzzo
A Five Planet Dawn (2016-01-30)

As January closes and in the coming days of February, early morning risers can spot the five naked-eye planets before dawn. Though some might claim to see six planets, in this seaside panoramic view all five celestial wanderers were found above the horizon along with a bright waning gibbous Moon on January 27. Nearly aligned along the plane of the ecliptic, but not along a line with the Sun, the five planets are spread well over 100 degrees across the sky. Just arriving on the predawn scene, fleeting Mercury stands above the southeastern horizon in the golden light of the approaching sunrise.

Image credit: Jose Antonio Hervás
MWC 922: The Red Square Nebula (2016-01-31)

What could cause a nebula to appear square? No one is quite sure. The hot star system known as MWC 922, however, appears to be embedded in a nebula with just such a shape.  The featured image combines infrared exposures from the Hale Telescope on Mt. Palomar in California, and the Keck-2 Telescope on Mauna Kea in Hawaii.  A leading progenitor hypothesis for the square nebula is that the central star or stars somehow expelled cones of gas during a late developmental stage. For MWC 922, these cones happen to incorporate nearly right angles and be visible from the sides.  Supporting evidence for the cone hypothesis includes radial spokes in the image that might run along the cone walls. Researchers speculate that the cones viewed from another angle would appear similar to the gigantic rings of supernova 1987A, possibly indicating that a star in MWC 922 might one day itself explode in a similar supernova.

Image credit: Peter Tuthill
(Sydney U.)
& James Lloyd (Cornell)
Find the Man in the Moon (2016-02-01)

Have you ever seen the Man in the Moon? This common question plays on the ability of humans to see pareidolia -- imagining familiar icons where they don't actually exist. The textured surface of Earth's full Moon is home to numerous identifications of iconic objects, not only in modern western culture but in world folklore throughout history. Examples, typically dependent on the Moon's perceived orientation, include the Woman in the Moon and the Rabbit in the Moon. One facial outline commonly identified as the Man in the Moon starts by imagining the two dark circular areas -- lunar maria -- here just above the Moon's center, to be the eyes.  Surprisingly, there actually is a man in this Moon image -- a close look will reveal a real person -- with a telescope -- silhouetted against the Moon. This featured well-planned image was taken in mid-January in Cadalso de los Vidrios in Madrid, Spain. Do you have a favorite object that you see in the Moon?

Image credit: Dani Caxete