juliensimon/nasa-apod huggingface dataset:
The Horsehead Nebula (2019-10-06)

The Horsehead Nebula is one of the most famous nebulae on the sky.  It is visible as the dark indentation to the red emission nebula in the center of the above photograph.  The horse-head feature is dark because it is really an opaque dust cloud that lies in front of the bright red emission nebula. Like clouds in Earth's atmosphere, this cosmic cloud has assumed a recognizable shape by chance.  After many thousands of years, the internal motions of the cloud will surely alter its appearance.  The emission nebula's red color is caused by electrons recombining with protons to form hydrogen atoms.  On the image left is the Flame Nebula, an orange-tinged nebula that also contains filaments of dark dust. Just to the lower left of the Horsehead nebula featured picture is a blueish reflection nebulae that preferentially reflects the blue light from nearby stars.

Image credit: Jos� Jim�nez Priego
Io Eclipse Shadow on Jupiter from Juno (2019-10-07)

What's that dark spot on Jupiter? It's the shadow of Jupiter's most volcanic moon Io. Since Jupiter shines predominantly by reflected sunlight, anything that blocks that light leaves a shadow.  If you could somehow be in that shadow, you would see a total eclipse of the Sun by Io.  Io's shadow is about 3600 kilometers across, roughly the same size as Io itself -- and only slightly larger than Earth's Moon. The featured image was taken last month by NASA's robotic Juno spacecraft currently orbiting Jupiter. About every two months, Juno swoops close by Jupiter, takes a lot of data and snaps a series of images -- some of which are made into a video. Among many other things, Juno has been measuring Jupiter's gravitational field, finding surprising evidence that Jupiter may be mostly a liquid. Under unexpectedly thick clouds, the Jovian giant may house a massive liquid hydrogen region that extends all the way to the center.
Sprite Lightning in HD (2019-10-08)

This phenomenon occurs in the sky over our heads, not the sea.  It is a type of lightning known as red sprite, and rarely has it ever been photographed in this detail.  Even though sprites have been recorded for over 30 years, their root cause remains unknown.  Some thunderstorms have them, but most don't. These mysterious bursts of light in the upper atmosphere momentarily resemble gigantic jellyfish. A few years ago high speed videos were taken detailing how red sprites actually develop.  The featured image was captured last month in high definition from Italy.  One unusual feature of sprites is that they are relatively cold -- they operate more like long fluorescent light tubes than hot compact light bulbs.  In general, red sprites take only a fraction of a second to occur and are best seen when powerful thunderstorms are visible from the side.

Image credit: Stephane Vetter
(TWAN)
NGC 7714: Starburst after Galaxy Collision (2019-10-09)

Is this galaxy jumping through a giant ring of stars?  Probably not.  Although the precise dynamics behind the featured image is yet unclear, what is clear is that the pictured galaxy, NGC 7714, has been stretched and distorted by a recent collision with a neighboring galaxy. This smaller neighbor, NGC 7715, situated off to the left of the featured frame, is thought to have charged right through NGC 7714. Observations indicate that the golden ring pictured is composed of millions of older Sun-like stars that are likely co-moving with the interior bluer stars. In contrast, the bright center of NGC 7714 appears to be undergoing a burst of new star formation.  The featured image was captured by the  Hubble Space Telescope.  NGC 7714 is located about 130 million light years away toward the constellation of the Two Fish (Pisces).  The interactions between these galaxies likely started about 150 million years ago and should continue for several hundred million years more, after which a single central galaxy may result.
Mid-Air Meteor and Milky Way (2019-10-10)

On September 24, a late evening commercial flight from Singapore to Australia offered stratospheric views of the southern hemisphere's night sky, if you chose a window seat. In fact, a well-planned seating choice with a window facing toward the Milky Way allowed the set up of a sensitive digital camera on a tripod mount to record the galaxy's central bulge in a series of 10 second long exposures.  By chance, one of the exposures caught this bright fireball meteor in the starry frame. Reflected along the wing of the A380 aircraft, the brilliant greenish streak is also internally reflected in the double layer window, producing a fainter parallel to the original meteor track. In the southern sky Jupiter is the bright source beneath the galactic bulge and seen next to a green beacon, just off the wing tip.

Image credit: Eric Wagner
Planet Earth at Blue Hour (2019-10-11)

Nature photographers and other fans of planet Earth always look forward to the blue hour. That's the transition in twilight, just before sunrise or after sunset, when the Sun is below the horizon but land and sky are still suffused with beautiful bluish hues of light. On August 8 this early morning blue hour panorama scanned along the clear western sky, away from the impending sunrise. A breathtaking scene, it looks down the slopes of Mt. Whitney, from along the John Muir Trail toward rugged peaks of planet Earth's Sierra Nevada mountain range. Above the horizon a faint pinkish band of back scattered sunlight, the anti-twilight arch or Belt of Venus, borders the falling grey shadow of Earth itself. Subtle bands of light across the clear sky are anti-crepuscular rays, defined by shadows of clouds near the sunward horizon. Actually following parallel lines they seem to converge along the horizon at the point opposite the rising Sun due to perspective.

Image credit: Matthias Ciprian
Interplanetary Earth (2019-10-12)

In an interplanetary first, on July 19, 2013 Earth was photographed on the same day from two other worlds of the Solar System, innermost planet Mercury and ringed gas giant Saturn. Pictured on the left, Earth is the pale blue dot just below the rings of Saturn, as captured by the robotic Cassini spacecraft then orbiting the outermost gas giant. On that same day people across planet Earth snapped many of their own pictures of Saturn. On the right, the Earth-Moon system is seen against the dark background of space as captured by the robotic MESSENGER spacecraft, then in Mercury orbit. MESSENGER took its image as part of a search for small natural satellites of Mercury, moons that would be expected to be quite dim. In the MESSENGER image, the Earth (left) and Moon (right) are overexposed and shine brightly with reflected sunlight. Destined not to return to their home world, both Cassini and MESSENGER have since retired from their missions of Solar System exploration.
A Stellar Jewel Box: Open Cluster NGC 290 (2019-10-13)

Jewels don't shine this bright -- only stars do.  Like gems in a jewel box, though, the stars of open cluster NGC 290 glitter in a beautiful display of brightness and color.   The photogenic cluster, pictured here, was captured in 2006 by the orbiting Hubble Space Telescope.  Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters of stars.  NGC 290 lies about 200,000  light-years distant in a neighboring galaxy called the Small Cloud of Magellan (SMC).   The open cluster contains hundreds of stars and spans about 65 light years across.  NGC 290 and other open clusters are good laboratories for studying how stars of different masses evolve, since all the open cluster's stars were born at about the same time.
Andromeda before Photoshop (2019-10-14)

What does the Andromeda galaxy really look like? The featured image shows how our Milky Way Galaxy's closest major galactic neighbor really appears in a long exposure through Earth's busy skies and with a digital camera that introduces normal imperfections.  The picture is a stack of 223 images, each a 300 second exposure, taken from a garden observatory in Portugal over the past year.  Obvious image deficiencies include bright parallel airplane trails, long and continuous satellite trails, short cosmic ray streaks, and bad pixels.  These imperfections were actually not removed with Photoshop specifically, but rather greatly reduced with a series of computer software packages that included Astro Pixel Processor, DeepSkyStacker, and PixInsight.  All of this work was done not to deceive you with a digital fantasy that has little to do with the real likeness of the Andromeda galaxy (M31), but to minimize Earthly artifacts that have nothing to do with the distant galaxy and so better recreate what M31 really does look like.
The Galaxy Above (2019-10-15)

Have you contemplated your home galaxy lately?  If your sky looked like this, perhaps you'd contemplate it more often! The featured picture is actually a composite of two images taken last month from the same location in south Brazil and with the same camera -- but a few hours apart.  The person in the image -- also the astrophotographer -- has much to see in the Milky Way Galaxy above. The central band of our home Galaxy stretches diagonally up from the lower left. This band is dotted with spectacular sights including dark nebular filaments, bright blue stars, and red nebulas.  Millions of fainter and redder stars fill in the deep Galactic background.  To the lower right of the Milky Way are the colorful gas and dust clouds of Rho Ophiuchi, featuring the bright orange star Antares.  On this night, just above and to the right of Antares was the bright planet Jupiter.  The sky is so old and so familiar that humanity has formulated many stories about it, some of which inspired this very picture.

Image credit: Rodrigo Guerra
BHB2007: A Baby Binary Star in Formation (2019-10-16)

How do binary stars form? To help find out, the Atacama Large Millimeter Array (ALMA) recently captured one of the highest resolution images yet taken of a binary star system in formation.  Most stars are not alone -- they typically form as part of a multiple star systems where star each orbits a common center of gravity.  The two bright spots in the featured image are small disks that surround the forming proto-stars in [BHB2007] 11, while the surrounding pretzel-shaped filaments are gas and dust that have been gravitationally pulled from a larger disk.  The circumstellar filaments span roughly the radius of the orbit of Neptune.  The BHB2007 system is a small part of the Pipe Nebula (also known as Barnard 59), a photogenic network of dust and gas that protrudes from Milky Way's spiral disk in the constellation of Ophiuchus. The binary star formation process should be complete within a few million years.
Moons of Saturn (2019-10-17)

On July 29, 2011 the Cassini spacecraft's narrow-angle camera took this snapshot and captured 5 of Saturn's moons, from just above the ringplane. Left to right are small moons Janus and Pandora respectively 179 and 81 kilometers across, shiny 504 kilometer diameter Enceladus, and Mimas, 396 kilometers across, seen just next to Rhea. Cut off by the right edge of the frame, Rhea is Saturn's second largest moon at 1,528 kilometers across. So how many moons does Saturn have? Twenty new found outer satellites bring its total to 82 known moons, and since Jupiter's moon total stands at 79, Saturn is the Solar System's new moon king. The newly announced Saturnian satellites are all very small, 5 kilometers or so in diameter, and most are in retrograde orbits inclined to Saturn's ringplane. You can help name Saturn's new moons, but you should understand the rules. Hint: A knowledge of Norse, Inuit, and Gallic mythology will help.
Interstellar Interloper 2I/Borisov (2019-10-18)

After the 2017 detecton of 1I/'Oumuamua, comet 2I/Borisov has become the second recognized interstellar interloper. Like 'Oumuamua, Borisov's measured hyperbolic trajectory and speed as it falls toward the Sun confirm that its origin is from beyond our Solar System. But while detailed observations indicate 'Oumuamua is a rocky body with differences from known Solar System objects, Borisov is definitely a far wandering comet. Taken on October 12, 2019 this Hubble Space Telescope image of Borisov reveals a familiar looking comet-like activity and concentration of dust around around its nucleus. Not resolved in the image, some estimates suggest the nucleus could be between 2 and 16 kilometers in diameter. At the time of the Hubble image, comet 2I/Borisov was about 418 million kilometers away. Borisov is still inbound though and will make its closest approach to the Sun on December 7 at a distance of about 300 million kilometers (2 Astronomical units).
All Female Spacewalk Repairs Space Station (2019-10-19)

The failed unit was beyond the reach of the robotic Canadarm2.  Therefore, this repair of the International Space Station would require humans. The humans on duty were NASA's Jessica Meir and Christina Koch. This was the fourth spacewalk for Koch, the first for Meir, and the first all-female spacewalk in human history.  The first woman to walk in space was Svetlana Savitskaya in 1984.  Koch (red stripe) and Meir are pictured hard at work on the P6 Truss, with solar panels and the darkness of space in the background.  Working over seven hours, the newly installed Battery Charge / Discharge Unit (BCDU) was successfully replaced and, when powered up, operated normally.
Pluto at Night (2019-10-20)

The night side of Pluto spans this shadowy scene, a stunning spacebased view with the Sun 4.9 billion kilometers (almost 4.5 light-hours) behind the dim and distant world. It was captured by far flung New Horizons in July of 2015. The spacecraft was at a range of some 21,000 kilometers from Pluto, about 19 minutes after its closest approach. A denizen of the Kuiper Belt in dramatic silhouette, the image also reveals Pluto's tenuous, surprisingly complex layers of hazy atmosphere. The crescent twilight landscape near the top of the frame includes southern areas of nitrogen ice plains now formally known as Sputnik Planitia and rugged mountains of water-ice in the Norgay Montes.
A Mercury Transit Music Video from SDO (2019-10-21)

What's that small black dot moving across the Sun? Mercury. Possibly the clearest view of Mercury crossing in front of the Sun in 2016 May was from Earth orbit. The Solar Dynamics Observatory obtained an uninterrupted vista recording it not only in optical light but also in bands of ultraviolet light. Featured here is a composite movie of the crossing set to music. Although the event might prove successful scientifically for better determining components of Mercury' ultra-thin atmosphere, the event surely proved successful culturally by involving people throughout the world in observing a rare astronomical phenomenon. Many spectacular images of this Mercury transit from around (and above) the globe were proudly displayed. The next transit of Mercury will take place in three weeks: on 2019 November 11.    Astrophysicists: Browse 2,000+ codes in the Astrophysics Source Code Library
Night Sky Reflections from the World's Largest Mirror (2019-10-22)

What's being reflected in the world's largest mirror?  Stars, galaxies, and a planet.  Many of these stars are confined to the grand arch that runs across the image, an arch that is the central plane of our home Milky Way Galaxy. Inside the arch is another galaxy -- the neighboring Large Magellanic Cloud (LMC).  Stars that are individually visible include Antares on the far left and Sirius on the far right. The planet Jupiter shines brightly just below Antares. The featured picture is composed of 15 vertical frames taken consecutively over ten minutes from the Uyuni Salt Flat in Bolivia. Uyuni Salt Flat (Salar de Uyuni) is the largest salt flat on Earth and is so large and so extraordinarily flat that, after a rain, it can become the world's largest mirror -- spanning 130 kilometers.  This expansive mirror was captured in early April reflecting each of the galaxies, stars, and planet mentioned above.

Image credit: Jheison Huerta
Starry Night by Vincent van Gogh (2019-10-23)

The painting Starry Night is one of the most famous icons of the night sky ever created.   The scene was painted by Vincent van Gogh in southern France in 1889.   The swirling style of Starry Night appears, to many, to make the night sky come alive.   Although van Gogh frequently portrayed real settings in his paintings, art historians do not agree on precisely what stars and planets are being depicted in Starry Night.   The style of Starry Night is post-impressionism, a popular painting style at the end of the nineteenth century.  The original Starry Night painting hangs in the Museum of Modern Art in New York City, New York, USA.   New: APOD Read to You by AI
Dark Seahorse in Cepheus (2019-10-24)

Light-years across, this suggestive shape known as the Seahorse Nebula appears in silhouette against a rich, luminous background of stars. Seen toward the royal northern constellation of Cepheus, the dusty, obscuring clouds are part of a Milky Way molecular cloud some 1,200 light-years distant. It is also listed as Barnard 150 (B150), one of 182 dark markings of the sky cataloged in the early 20th century by astronomer E. E. Barnard. Packs of low mass stars are forming within from collapsing cores only visible at long infrared wavelengths. Still, colorful stars in Cepheus add to the pretty, galactic skyscape.

Image credit: Sergio Kaminsky
The Ghosts of Cassiopeia (2019-10-25)

These bright rims and flowing shapes look ghostly on a cosmic scale. A telescopic view toward the constellation Cassiopeia, the colorful skyscape features swept-back, comet-shaped clouds IC 59 (left) and IC 63. About 600 light-years distant, the clouds aren't actually ghosts. They are slowly disappearing though, under the influence of energetic radiation from hot,luminous star gamma Cas. Gamma Cas is physically located only 3 to 4 light-years from the nebulae, the bright star just above and left in the frame. Slightly closer to gamma Cas, IC 63 is dominated by red H-alpha light emitted as hydrogen atoms ionized by the star's ultraviolet radiation recombine with electrons. Farther from the star, IC 59 shows proportionally less H-alpha emission but more of the characteristic blue tint of dust reflected star light. The field of view spans over 1 degree or 10 light-years at the estimated distance of gamma Cas and friends.

Image credit: Cassiopeia
Gravity's Grin (2019-10-26)

Albert Einstein's general theory of relativity, published over 100 years ago, predicted the phenomenon of gravitational lensing. And that's what gives these distant galaxies such a whimsical appearance, seen through the looking glass of X-ray and optical image data from the Chandra and Hubble space telescopes. Nicknamed the Cheshire Cat galaxy group, the group's two large elliptical galaxies are suggestively framed by arcs. The arcs are optical images of distant background galaxies lensed by the foreground group's total distribution of gravitational mass. Of course, that gravitational mass is dominated by dark matter. The two large elliptical "eye" galaxies represent the brightest members of their own galaxy groups which are merging. Their relative collisional speed of nearly 1,350 kilometers/second heats gas to millions of degrees producing the X-ray glow shown in purple hues. Curiouser about galaxy group mergers? The Cheshire Cat group grins in the constellation Ursa Major, some 4.6 billion light-years away.
Ghost Aurora over Canada (2019-10-27)

What does this aurora look like to you? While braving the cold to watch the skies above northern Canada early one morning in 2013, a most unusual aurora appeared.  The aurora definitely appeared to be shaped like something , but what? Two ghostly possibilities recorded by the astrophotographer were "witch" and "goddess of dawn", but please feel free to suggest your own Halloween-enhanced impressions. Regardless of fantastical pareidolic interpretations, the pictured aurora had a typical green color and was surely caused by the scientifically commonplace action of high energy particles from space interacting with oxygen in Earth's upper atmosphere.  In the image foreground, at the bottom, is a frozen Alexandra Falls, while evergreen trees cross the middle.

Image credit: Yuichi Takasaka,
TWAN
The Space Station Crosses a Spotless Sun (2019-10-28)

Typically, the International Space Station is visible only at night.  Slowly drifting across the night sky as it orbits the Earth, the International Space Station (ISS) can be seen as a bright spot about once a month from many locations.  The ISS is then visible only just after sunset or just before sunrise because it shines by reflected sunlight -- once the ISS enters the Earth's shadow, it will drop out of sight. The only occasion when the ISS is visible during the day is when it passes right in front of the Sun. Then, it passes so quickly that only cameras taking short exposures can visually freeze the ISS's silhouette onto the background Sun. The featured picture did exactly that -- it is actually a series of images taken a month ago from Santa Fe, Argentina with perfect timing.  This image series was later combined with a separate image highlighting the texture of the spotless Sun, and an image bringing up the Sun's prominences around the edge. At an unusually low Solar Minimum, the Sun has gone without sunspots now for most of 2019.    Follow APOD in English on: Instagram, Facebook,  Reddit, or Twitter

Image credit: Eduardo Schaberger Poupeau
Curiosity Rover Finds a Clay Cache on Mars (2019-10-29)

Why is there clay on Mars? On Earth, clay can form at the bottom of a peaceful lake when specific minerals trap water.  At the pictured site on Mars, the robotic rover Curiosity drilled into two rocks and found the highest concentration of clay yet.  The clay cache is considered addition evidence that Gale Crater once held water in the distant past.  Pictured, 57 images taken by Curiosity have been combined into a selfie. The images were taken by a camera at the end of its robotic arm. Many details of the car-sized rover are visible, including its rugged wheels, numerous scientific instruments, and a high mast that contains camera "eyes", one of which can shoot out an infrared laser beam.  Curiosity continues to roll around and up Mount Sharp -- in the center of Gale Crater -- in a search for new clues about the ancient history of Mars and whether or not the red planet once had conditions that could support life.
M42: Inside the Orion Nebula (2019-10-30)

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 featured deep image in assigned colors highlighted by emission in oxygen and hydrogen, wisps and sheets of dust and gas are particularly evident.  The Great Nebula in Orion can be found with the unaided eye near 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 much 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: Josep M. Drudis &
Don Goldman