juliensimon/nasa-apod huggingface dataset:
Aurora over Clouds (2021-05-30)

Auroras usually occur high above the clouds.  The auroral glow is created when fast-moving particles ejected from the Sun impact the Earth's magnetosphere, from which charged particles spiral along the Earth's magnetic field to strike atoms and molecules high in the Earth's atmosphere.  An oxygen atom, for example, will glow in the green light commonly emitted by an aurora after being energized by such a collision.  The lowest part of an aurora will typically occur about 100 kilometers up, while most clouds exist only below about 10 kilometers.  The relative heights of clouds and auroras are shown clearly in the featured picture in 2015 from Dyrholaey, Iceland. There, a determined astrophotographer withstood high winds and initially overcast skies in an attempt to capture aurora over a picturesque lighthouse, only to take, by chance, the featured picture including elongated lenticular clouds, along the way.    Follow APOD on Instagram in: English, Farsi, Indonesian, Persian, or Portuguese

Image credit: Daniele Boffelli
Mimas: Small Moon with a Big Crater (2021-05-31)

Whatever hit Mimas nearly destroyed it.  What remains is one of the largest impact craters on one of Saturn's smallest round moons.  Analysis indicates that a slightly larger impact would have destroyed Mimas entirely.  The huge crater, named Herschel after the 1789 discoverer of Mimas, Sir William Herschel, spans about 130 kilometers and is featured here. Mimas' low mass produces a surface gravity just strong enough to create a spherical body but weak enough to allow such relatively large surface features. Mimas is made of mostly water ice with a smattering of rock - so it is accurately described as a big dirty snowball. The featured image was taken during the closest-ever flyby of the robot spacecraft Cassini past Mimas in 2010 while in orbit around Saturn.   Interactive: Take a trek across Mimas

Image credit: NASA, 
JPL-Caltech,
Space Science Institute,
Cassini
Satellites over Orion (2021-06-01)

What are those streaks across Orion? They are reflections of sunlight from numerous Earth-orbiting satellites. Appearing by eye as a series of successive points floating across a twilight sky, the increasing number of communications satellites, including SpaceX Starlink satellites, are causing concern among many astronomers. On the positive side, Starlink and similar constellations make the post-sunset sky more dynamic, satellite-based global communications faster, and help provide digital services to currently underserved rural areas.  On the negative side, though, these low Earth-orbit satellites make some deep astronomical imaging programs more difficult, in particular observing programs that need images taken just after sunset and just before dawn.  Planned future satellite arrays that function in higher orbits may impact investigations of the deep universe planned for large ground-based telescopes at any time during the night.  The streaks across Orion are not from Starlink but rather satellites in high geosynchronous orbit.  The featured picture, taken in 2019 December, is a digital combination of over 65 3-minutes exposures, with some images taken to highlight the background Orion Nebula, while others to feature the passing satellites.    SatCon2 Wokshop 12-16 July 2021: Mitigating Satellite Constellations
The Galactic Center in Stars, Gas, and Magnetism (2021-06-02)

What's going on near the center of our galaxy? To help find out, a newly detailed panorama has been composed that explores regions just above and below the galactic plane in radio and X-ray light.  X-ray light taken by the orbiting Chandra Observatory is shown in orange (hot), green (hotter), and purple (hottest) and superposed with a highly detailed image in radio waves, shown in gray, acquired by the MeerKAT array.  Interactions are numerous and complex. Galactic beasts such as expanding supernova remnants, hot winds from newly formed stars, unusually strong and colliding magnetic fields, and a central supermassive black hole are all battling in a space only 1000 light years across.  Thin bright stripes appear to result from twisting and newly connecting magnetic fields in colliding regions, creating an energetic type of inner galactic space weather with similarities to that created by our Sun.  Continued observations and study hold promise to not only shed more light on the history and evolution of our own galaxy -- but all galaxies.
Millions of Stars in Omega Centauri (2021-06-03)

Globular star cluster Omega Centauri, also known as NGC 5139, is some 15,000 light-years away. The cluster is packed with about 10 million stars much older than the Sun within a volume about 150 light-years in diameter. It's the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way. Omega Centauri's red giant stars (with a yellowish hue) are easy to pick out in this sharp, color telescopic view.

Image credit: Ignacio Diaz Bobillo
Blood Monster Moon (2021-06-04)

On May 26, the Full Flower Moon was caught in this single exposure as it emerged from Earth's shadow and morning twilight began to wash over the western sky. Posing close to the horizon near the end of totality, an eclipsed lunar disk is framed against bare oak trees at Pinnacles National Park in central California. The Earth's shadow isn't completely dark though. Faintly suffused with sunlight scattered by the atmosphere, the inner shadow gives the totally eclipsed moon a reddened appearance and the very dramatic popular moniker of a Blood Moon. Still, the monstrous visage of a gnarled tree in silhouette made this view of a total lunar eclipse even scarier.

Image credit: Chirag Upreti
The Shining Clouds of Mars (2021-06-05)

The weathered and layered face of Mount Mercou looms in the foreground of this mosaic from the Curiosity Mars rover's Mast Camera. Made up of 21 individual images the scene was recorded just after sunset on March 19, the 3,063rd martian day of Curiosity's on going exploration of the Red Planet. In the martian twilight high altitude clouds still shine above, reflecting the light from the Sun below the local horizon like the noctilucent clouds of planet Earth. Though water ice clouds drift through the thin martian atmosphere, these wispy clouds are also at extreme altitudes and could be composed of frozen carbon dioxide, crystals of dry ice. Curiosity's Mast Cam has also imaged iridescent or mother of pearl clouds adding subtle colors to the martian sky.
A Distorted Sunrise Eclipse (2021-06-06)

Yes, but have you ever seen a sunrise like this?  Here, after initial cloudiness, the Sun appeared to rise in two pieces and during partial eclipse, causing the photographer to describe it as the most stunning sunrise of his life.  The dark circle near the top of the atmospherically-reddened Sun is the Moon -- but so is the dark peak just below it.  This is because along the way, the Earth's atmosphere had a layer of unusually warm air over the sea which acted like a gigantic lens and created a second image.  For a normal sunrise or sunset, this rare phenomenon of atmospheric optics is known as the Etruscan vase effect. The featured picture was captured in December 2019 from Al Wakrah, Qatar.  Some observers in a narrow band of Earth to the east were able to see a full annular solar eclipse -- where the Moon appears completely surrounded by the background Sun in a ring of fire.  The next solar eclipse, also an annular eclipse for well-placed observers, will occur later this week on  June 10.

Image credit: Elias Chasiotis
A Bright Nova in Cassiopeia (2021-06-07)

What’s that new spot of light in Cassiopeia? A nova.  Although novas occur frequently throughout the universe, this nova, known as Nova Cas 2021 or V1405 Cas, became so unusually bright in the skies of Earth last month that it was visible to the unaided eye.  Nova Cas 2021 first brightened in mid-March but then, unexpectedly, became even brighter in mid-May and remained quite bright for about a week.  The nova then faded back to early-May levels,  but now is slightly brightening again and remains visible through binoculars.  Identified by the arrow, the nova occurred toward the constellation of Cassiopeia, not far from the Bubble Nebula.  A nova is typically caused by a thermonuclear explosion on the surface of a white dwarf star that is accreting matter from a binary-star companion -- although details of this outburst are currently unknown.  Novas don't destroy the underlying star, and are sometimes seen to recur.  The featured image was created from 14 hours of imaging from Detroit, Michigan, USA.  Both professional and amateur astronomers will likely continue to monitor Nova Cas 2021 and hypothesize about details of its cause.

Image credit: Chuck Ayoub
A Face in the Clouds of Jupiter from Juno (2021-06-08)

What do you see in the clouds of Jupiter? On the largest scale, circling the planet, Jupiter has alternating light zones and reddish-brown belts. Rising zone gas, mostly hydrogen and helium, usually swirls around regions of high pressure. Conversely, falling belt gas usually whirls around regions of low pressure, like cyclones and hurricanes on Earth.  Belt storms can form into large and long-lasting white ovals and elongated red spots. NASA's robotic Juno spacecraft captured most of these cloud features in 2017 during perijove 6, its sixth pass over the giant planet in its looping 2-month orbit.  But it is surely not these clouds themselves that draws your attention to the displayed image, but rather their arrangement.  The face that stands out, nicknamed Jovey McJupiterFace, lasted perhaps a few weeks before the neighboring storm clouds rotated away. Juno has now completed 33 orbits around Jupiter and just yesterday made a close pass near Ganymede, our Solar System's largest moon.
A Total Lunar Eclipse Corona (2021-06-09)

This moon appears multiply strange.  This moon was a full moon, specifically called a Flower Moon at this time of the year.  But that didn't make it strange -- full moons occur once a month (moon-th).  This moon was a supermoon, meaning that it reached its full phase near its closest approach to the Earth in its slightly elliptical orbit.  Somewhat strange, a supermoon appears a bit larger and brighter than the average full moon -- and enables it to be called a Super Flower Moon.  This moon was undergoing a total lunar eclipse. An eclipsed moon can look quite strange, being dark, unevenly lit, and, frequently, red -- sometimes called blood red. Therefore, this moon could be called a Super Flower Blood Moon. This moon was seen through thin clouds. These clouds created a faint corona around the moon, making it look not only strange, but colorful.  This moon was imaged so deeply that the heart of the Milky Way galaxy, far in the background, was visible to its lower right.  This moon, this shadow, this galaxy and these colors were all captured last month near Cassilis, NSW, Australia -- with a single shot. (Merged later with two lower shots that better capture the Milky Way.)   Details: Annular Solar Eclipse Tomorrow  Gallery: Total Eclipse of the Super Flower Blood Moon

Image credit: Helmut Eder
Circular Sun Halo (2021-06-10)

Want to see a ring around the Sun? It's easy to do in daytime skies around the world. Created by randomly oriented ice crystals in thin high cirrus clouds, circular 22 degree halos are visible much more often than rainbows. This one was captured by smart phone photography on May 29 near Rome, Italy. Carefully blocking the Sun, for example with a finger tip, is usually all that it takes to reveal the common bright halo ring. The halo's characteristic angular radius is about equal to the span of your hand, thumb to little finger, at the end of your outstretched arm.  Want to see a ring of fire eclipse? That's harder. The spectacular annular phase of today's (June 10) solar eclipse, known as a ring of fire, was briefly visible only when standing along the Moon's narrow shadow track that passes over parts of northern Canada, Greenland, the Arctic, and eastern Russia. The solar eclipse was partial though, when seen from broader regions, including northern Asia, Europe, and parts of the US.

Image credit: Vincenzo Mirabella
Eclipse Flyby (2021-06-11)

On June 10 a New Moon passed in front of the Sun. In silhouette only two days after reaching apogee, the most distant point in its elliptical orbit, the Moon's small apparent size helped create an annular solar eclipse. The brief but spectacular annular phase of the eclipse shows a bright solar disk as a ring of fire when viewed along its narrow, northerly shadow track across planet Earth. Cloudy early morning skies along the US east coast held gorgeous views of a partially eclipsed Sun though. Rising together Moon and Sun are captured in a sequence of consecutive frames near maximum eclipse in this digital composite, seen from Quincy Beach south of Boston, Massachusetts. The serendipitous sequence follows the undulating path of a bird in flight joining the Moon in silhouette with the rising Sun.   Notable images submitted to APOD: This week's solar eclipse

Image credit: Zev Hoover
Eclipse on the Water (2021-06-12)

clipses tend to come in pairs. Twice a year, during an eclipse season that lasts about 34 days, Sun, Moon, and Earth can nearly align. Then the full and new phases of the Moon separated by just over 14 days create a lunar and a solar eclipse. Often partial eclipses are part of any eclipse season. But sometimes the alignment at both new moon and full moon phases during a single eclipse season is close enough to produce a pair of both total (or a total and an annular) lunar and solar eclipses. For this eclipse season, the New Moon following the Full Moon's total lunar eclipse on May 26 did produce an annular solar eclipse along its northerly shadow track. That eclipse is seen here in a partially eclipsed sunrise on June 10, photographed from a fishing pier in Stratford, Connecticut in the northeastern US.   Notable images submitted to APOD: June 10 solar eclipse

Image credit: Elliot Severn
A Supercell Thunderstorm Over Texas (2021-06-13)

Is that a cloud or an alien spaceship?  It's an unusual and sometimes dangerous type of thunderstorm cloud called a supercell. Supercells may spawn damaging tornados, hail, downbursts of air, or drenching rain.  Or they may just look impressive. A supercell harbors a mesocyclone -- a rising column of air surrounded by drafts of falling air.  Supercells could occur over many places on Earth but are particularly common in  Tornado Alley of the USA. Featured here are four time-lapse sequences of a supercell in 2013 rotating above and moving across Booker, Texas.  Captured in the video are new clouds forming near the storm center, dust swirling on the ground, lightning flashing in the upper clouds, all while the impressively sculptured complex rotates ominously.  Finally, after a few hours, as shown in the final sequence, dense rain falls as the storm begins to die out.   Notable images submitted to APOD: Last week's solar eclipse

Image credit: Mike Olbinski; 
 Music:  Impact Lento (Kevin MacLeod, Incompetech)
Ganymede from Juno (2021-06-14)

What does the largest moon in the Solar System look like?  Jupiter's moon Ganymede, larger than even Mercury and Pluto, has an icy surface speckled with bright young craters overlying a mixture of older, darker, more cratered terrain laced with grooves and ridges.  The cause of the grooved terrain remains a topic of research, with a leading hypothesis relating it to shifting ice plates.  Ganymede is thought to have an ocean layer that contains more water than Earth -- and might contain life.  Like Earth's Moon, Ganymede keeps the same face towards its central planet, in this case Jupiter.  The featured image was captured last week by NASA's robotic Juno spacecraft as it passed only about 1000 kilometers above the immense moon.  The close pass reduced Juno's orbital period around Jupiter from 53 days to 43 days.  Juno continues to study the giant planet's high gravity, unusual magnetic field, and complex cloud structures.    Last week's solar eclipse: Notable images submitted to APOD
Zhurong: New Rover on Mars (2021-06-15)

There's a new rover on Mars. In mid-May, China's Tianwen-1 mission delivered the Zhurong rover onto the red planet.  As Mars means Planet of Fire in Chinese, the Zhurong rover's name means, roughly, God of Fire in Chinese mythology.  Zhurong landed in northern Utopia Planitia, the largest known impact basin in the Solar System, and an area reported to have much underground ice. Among many other scientific instruments, Zhurong carries ground-penetrating radar that can detect ice buried even 100-meters deep. Car-sized Zhurong is pictured here next to its landing base.  The image was snapped by a remote camera deployed by the rolling rover. Zhurong's planned 90-day mission includes studying the geology, soil, and atmosphere of Mars in Utopia Planitia.
Scorpius Enhanced (2021-06-16)

If Scorpius looked this good to the unaided eye, humans might remember it better.  Scorpius more typically appears as a few bright stars in a well-known but rarely pointed out zodiacal constellation. To get a spectacular image like this, though, one needs a good camera, a dark sky, and some sophisticated image processing.  The resulting digitally-enhanced image shows many breathtaking features.  Diagonal across the image right is part of the plane of our Milky Way Galaxy.   Visible there are vast clouds of bright stars and long filaments of dark and intricate dust.  Rising vertically on the image left are dark dust bands known as the Dark River.  Several of the bright stars on the left are part of Scorpius' head and claws, and include the bright star Antares.  Numerous red emission nebulas, blue reflection nebulas, and dark filaments became visible as the deep 17-hour expo image developed. Scorpius appears prominently in southern skies after sunset during the middle of the year.

Image credit: Stefan Lenz
NGC 6888: The Crescent Nebula (2021-06-17)

NGC 6888, also known as the Crescent Nebula, is a about 25 light-years across blown by winds from its central, bright, massive star. A triumvirate of astroimagers ( Joe, Glenn, Russell) created this sharp portrait of the cosmic bubble. Their telescopic collaboration collected over 30 hours of narrow band image data isolating light from hydrogen and oxygen atoms. The oxygen atoms produce the blue-green hue that seems to enshroud the detailed folds and filaments. Visible within the nebula, NGC 6888's central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun's mass every 10,000 years.  The nebula's complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.

Image credit: Joe Navara
Devil Horns from a Ring of Fire (2021-06-18)

Atmospheric refraction flattened the solar disk and distorted its appearance in this telescopic view of an Atlantic sunrise on June 10. From Belmar, New Jersey on the US east coast, the scene was recorded at New Moon during this season's annular solar eclipse. The Moon in partial silhouette gives the rising Sun its crescent shape reminding some of the horns of the devil (or maybe a flying canoe ...). But at its full annular phase this eclipsed Sun looked like a ring of fire in the heavens. June's annular solar eclipse followed on the heels of the total lunar eclipse of late May's Full Moon. Of course, that total lunar eclipse was a dramatic red Blood Moon eclipse.

Image credit: Madhup Rathi
Northern Summer Twilight (2021-06-19)

Nights grow shorter and days grow longer as the summer solstice approaches in the north. Usually seen at high latitudes in summer months, noctilucent or night shining clouds begin to make their appearance.  Drifting near the edge of space about 80 kilometers above the Earth's surface, these icy clouds were still reflecting the sunlight on June 14. Though the Sun was below the horizon as seen north of Forrest, Manitoba, Canada, they were caught in a single exposure of a near midnight twilight sky. Multiple exposures of the foreground track the lower altitude flash of fireflies, another fleeting apparition shining in the summer night.

Image credit: Justin Anderson
Sunrise Solstice over Stonehenge (2021-06-20)

Today the Sun reaches its northernmost point in planet Earth's sky.  Called a solstice, many cultures mark this date as a change of seasons -- from spring to summer in Earth's Northern Hemisphere and from fall to winter in Earth's Southern Hemisphere.  Precisely, the single time of solstice occurs today for some parts of the world, but tomorrow for other regions. The featured image was taken during the week of the 2008 summer solstice at Stonehenge in United Kingdom, and captures a picturesque sunrise involving fog, trees, clouds, stones placed about 4,500 years ago, and a 4.5 billion year old large glowing orb. Even given the precession of the Earth's rotational axis over the millennia, the Sun continues to rise over Stonehenge in an astronomically significant way.

Image credit: Max Alexander, 
STFC, 
SPL
The Tadpole Galaxy from Hubble (2021-06-21)

Why does this galaxy have such a long tail?  In this stunning vista, based on image data from the Hubble Legacy Archive, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation of the Dragon (Draco). Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from right to left in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper right. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.   APOD in world languages: Arabic, Bulgarian, Catalan, Chinese (Beijing), Chinese (Taiwan), Croatian, Czech, Dutch, Farsi, French, German, Hebrew, Indonesian, Japanese, Korean, Montenegrin, Polish, Russian, Serbian, Slovenian,  Spanish, Taiwanese, Turkish, Turkish, and  Ukrainian
HD 163296: Jet from a Star in Formation (2021-06-22)

How are jets created during star formation? No one is sure, although recent images of the young star system HD 163296 are quite illuminating. The central star in the featured image is still forming but seen already surrounded by a rotating disk and an outward moving jet. The disk is shown in radio waves taken by the Atacama Large Millimeter Array (ALMA) in Chile, and show gaps likely created by the gravity of very-young planets.  The jet, shown in visible light taken by the Very Large Telescope (VLT, also in Chile), expels fast-moving gas -- mostly hydrogen -- from the disk center.  The system spans hundreds of times the Earth-Sun distance (au).  Details of these new observations are being interpreted to  bolster conjectures that the jets are generated and shaped, at least in part, by magnetic fields in the rotating disk. Future observations of HD 163296 and other similar star-forming systems may help fill in details.    Astrophysicists: Browse 2,500+ codes in the Astrophysics Source Code Library