juliensimon/nasa-apod huggingface dataset:
Aurora Over White Dome Geyser (2022-02-20)

Sometimes both heaven and Earth erupt. Colorful auroras erupted unexpectedly a few years ago, with green aurora appearing near the horizon and brilliant bands of red aurora blooming high overhead.  A bright Moon lit the foreground of this picturesque scene, while familiar stars could be seen far in the distance.  With planning, the careful astrophotographer shot this image mosaic in the field of White Dome Geyser in Yellowstone National Park in the western USA. Sure enough, just after midnight, White Dome erupted -- spraying a stream of water and vapor many meters into the air. Geyser water is heated to steam by scalding magma several kilometers below, and rises through rock cracks to the surface. About half of all known geysers occur in Yellowstone National Park. Although the geomagnetic storm that caused the auroras subsided within a day, eruptions of White Dome Geyser continue about every 30 minutes.

Image credit: Robert Howell
Barred Spiral Galaxy NGC 6217 (2022-02-21)

Many spiral galaxies have bars across their centers.  Even our own Milky Way Galaxy is thought to have a modest central bar. Prominently barred spiral galaxy NGC 6217, featured here, was captured in spectacular detail in this image taken by the Advanced Camera for Surveys on the orbiting Hubble Space Telescope in 2009. Visible are dark filamentary dust lanes, young clusters of bright blue stars, red emission nebulas of glowing hydrogen gas, a long bar of stars across the center, and a bright active nucleus that likely houses a supermassive black hole.  Light takes about 60 million years to reach us from NGC 6217, which spans about 30,000 light years across and can be found toward the constellation of the Little Bear (Ursa Minor).   APOD in world languages: Arabic, Bulgarian, Catalan, Chinese (Beijing), Chinese (Taiwan), Croatian, Czech, Dutch, French, French (Canada), German, Hebrew, Indonesian, Japanese, Korean, Montenegrin, Polish, Russian, Serbian, Slovenian,  Spanish, Taiwanese, Turkish, Turkish, and  Ukrainian
Illustration: An Early Quasar (2022-02-22)

What did the first quasars look like?  The nearest quasars are now known to involve supermassive black holes in the centers of active galaxies.  Gas and dust that falls toward a quasar glows brightly, sometimes outglowing the entire home galaxy.  The quasars that formed in the first billion years of the universe are more mysterious, though. Featured, recent data has enabled an artist's impression of an early-universe quasar as it might have been: centered on a massive black hole, surrounded by sheets of gas and an accretion disk, and expelling a powerful jet. Quasars are among the most distant objects we see and give humanity unique information about the early and intervening universe. The oldest quasars currently known are seen at just short of redshift 8 -- only 700 million years after the Big Bang -- when the universe was only a few percent of its current age.
Orion over Green Bank (2022-02-23)

What will the huge Green Bank Telescope discover tonight? Pictured, the Robert C. Byrd Green Bank Telescope (GBT) on the lower right is the largest fully-pointable single-dish radio telescope in the world. With a central dish larger than a football field, the GBT is nestled in the hills of West Virginia, USA in a radio quiet zone where the use of cell phones, WiFi emitters, and even microwave ovens are limited. The GBT explores our universe not only during the night -- but during the day, too, since the daytime sky is typically dark in radio waves.  Taken in late January, the featured image was planned for months to get the setting location of Orion just right.  The image is a composite of a foreground shot taken over a kilometer away from the GBT, and a background shot built up of long exposures during the previous night. The deep background image of Orion is fitting because the GBT is famous for, among many discoveries, mapping the unusual magnetic field in the Orion Molecular Cloud Complex.

Image credit: Dave Green
Beautiful Albireo AB (2022-02-24)

Beta Cygni is a single bright star to the naked eye. About 420 light-years away it marks the foot of the Northern Cross, famous asterism in the constellation Cygnus. But a view through the eyepiece of a small telescope will transform it into a beautiful double star, a treasure of the night sky in blue and gold. Beta Cygni is also known as Albireo, designated Albireo AB to indicate its two bright component stars. Their visually striking color difference is illustrated in this telescopic snapshot, along with their associated visible spectrum of starlight shown in insets to the right. Albireo A, top inset, shows the spectrum of a K-type giant star, cooler than the Sun and emitting most of its energy at yellow and red wavelengths. Below, Albireo B has the spectrum of a main sequence star much hotter than the Sun, emitting more energy in blue and violet. Albireo A is known to be a binary star, two stars together orbiting a common center of mass, though the two stars are too close together to be seen separately with a small telescope. Well-separated Albireo A and B most likely represent an optical double star and not a physical binary system because the two components have clearly different measured motions through space.

Image credit: Robert Eder
Perseverance Sol 354 (2022-02-25)

This Navcam mosaic from Perseverance looks out over the car-sized rover's deck, across the floor of Jezero crater on Mars. Frames used to construct the mosaic view were captured on mission sol 354. That corresponds to Earth calendar date February 17, 2022, nearly one Earth year after the rover's landing. With a mass of over 1,000 kilograms, six-wheeled Perseverance is the heaviest rover to touch down on Mars. During its first year of exploration the rover has collected six (so far) rock core samples for later return to planet Earth, served as the base station for Ingenuity, the first helicopter on Mars, and tested MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment), converting some of the Red Planet’s thin, carbon dioxide-rich atmosphere into oxygen.
Nearby Spiral Galaxy NGC 4945 (2022-02-26)

Large spiral galaxy NGC 4945 is seen nearly edge-on in this cosmic galaxy close-up. It's almost the size of our Milky Way Galaxy. NGC 4945's own dusty disk, young blue star clusters, and pink star forming regions stand out in the colorful telescopic frame. About 13 million light-years distant toward the expansive southern constellation Centaurus, NGC 4945 is only about six times farther away than Andromeda, the nearest large spiral galaxy to the Milky Way. Though this galaxy's central region is largely hidden from view for optical telescopes, X-ray and infrared observations indicate significant high energy emission and star formation in the core of NGC 4945. Its obscured but active nucleus qualifies the gorgeous island universe as a Seyfert galaxy and home to a central supermassive black hole.

Image credit: Dietmar Hager
Earthrise 1: Historic Image Remastered (2022-02-27)

"Oh my God! Look at that picture over there! Here's the Earth coming up. Wow is that pretty!" Soon after that pronouncement, about 53 years ago, one of the most famous images ever taken was snapped from the orbit of the Moon. Now known as "Earthrise", the iconic image shows the Earth rising above the limb of the Moon, as taken by the crew of Apollo 8.  But the well-known Earthrise image was actually the  second image taken of the Earth rising above the lunar limb -- it was just the first in color.  With modern digital technology, however, the real first Earthrise image -- originally in black and white -- has now been remastered to have the combined resolution and color of the first three images.  Behold! The featured image is a close-up of the picture that Apollo 8 astronaut Bill Anders was talking about. Thanks to modern technology and human ingenuity, now we can all see it. (Historical note: A different historic black & white image of the Earth setting behind the lunar limb was taken by the robotic Lunar Orbiter 1 two years earlier.)
Direct Projection: The Moon in My Hands (2022-02-28)

You don't have to look through a telescope to know where it's pointing. Allowing the telescope to project its image onto a large surface can be useful because it dilutes the intense brightness of very bright sources. Such dilution is useful for looking at the Sun, for example during a solar eclipse. In the featured single-exposure image, though, it is a too-bright full moon that is projected. This February full moon occurred two weeks ago and is called the Snow Moon by some northern cultures.  The projecting instrument is the main 62-centimeter telescope at the Saint-Véran Observatory high in the French Alps. Seeing a full moon directly is easier because it is not too bright, although you won't see this level of detail.  Your next chance will occur on March 17.

Image credit: Jeff Graphy
Dueling Bands in the Night (2022-03-01)

What are these two bands in the sky? The more commonly seen band is the one on the right and is the central band of our Milky Way galaxy. Our Sun orbits in the disk of this spiral galaxy, so that from inside, this disk appears as a band of comparable brightness all the way around the sky. The Milky Way band can also be seen all year -- if out away from city lights.  The less commonly seem band, on the left, is zodiacal light -- sunlight reflected from dust orbiting the Sun in our Solar System.  Zodiacal light is brightest near the Sun and so is best seen just before sunrise or just after sunset.  On some evenings in the north, particularly during the months of March and April, this ribbon of zodiacal light can appear quite prominent after sunset.  It was determined only this century that zodiacal dust was mostly expelled by comets that have passed near Jupiter.  Only on certain times of the year will the two bands be seen side by side, in parts of the sky, like this.  The featured image, including the Andromeda galaxy and a meteor, was captured in late January over a frozen lake in Kanding, Sichuan, China.

Image credit: Jeff Dai
(TWAN)
Record Prominence Imaged by Solar Orbiter (2022-03-02)

What's happened to our Sun?  Last month, it produced the largest prominence ever imaged together with a complete solar disk. The record image, featured, was captured in ultraviolet light by the Sun-orbiting Solar Orbiter spacecraft. A quiescent solar prominence is a cloud of hot gas held above the Sun's surface by the Sun's magnetic field.  This solar prominence was huge -- spanning a length rivaling the diameter of the Sun itself. Solar prominences may erupt unpredictably and expel hot gas into the Solar System via a Coronal Mass Ejection (CME).  When a CME strikes the Earth and its magnetosphere, bright auroras may occur. This prominence did produce a CME, but it was directed well away from the Earth. Although surely related to the Sun's changing magnetic field, the energy mechanism that creates and sustains a solar prominence remains a topic of research.
Spiral Galaxy NGC 2841 (2022-03-03)

A mere 46 million light-years distant, spiral galaxy NGC 2841 can be found in the northern constellation of Ursa Major. This deep view of the gorgeous island universe was captured during 32 clear nights in November, December 2021 and January 2022. It shows off a striking yellow nucleus, galactic disk, and faint outer regions.  Dust lanes, small star-forming regions, and young star clusters are embedded in the patchy, tightly wound spiral arms. In contrast, many other spirals exhibit grand, sweeping arms with large star-forming regions.  NGC 2841 has a diameter of over 150,000 light-years, even larger than our own Milky Way. X-ray images suggest that resulting winds and stellar explosions create plumes of hot gas extending into a halo around NGC 2841.

Image credit: Vitali Pelenjow
The Multiwavelength Crab (2022-03-04)

The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from massive star's death explosion, witnessed on planet Earth in 1054 AD. This brave new image offers a 21st century view of the Crab Nebula by presenting image data from across the electromagnetic spectrum as wavelengths of visible light. From space, Chandra (X-ray) XMM-Newton (ultraviolet), Hubble (visible), and Spitzer (infrared), data are in purple, blue, green, and yellow hues. From the ground, Very Large Array radio wavelength data is shown in red. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.
Interstellar Comet 2I Borisov (2022-03-05)

From somewhere else in the Milky Way galaxy, Comet 2I/Borisov was just visiting the Solar System. Discovered by amateur astronomer Gennady Borisov on August 30, 2019, the first known interstellar comet is seen in these two Hubble Space Telescope images from November and December 2019. On the left, a distant background galaxy near the line-of-sight to Borisov is blurred as Hubble tracked the speeding comet and dust tail about 327 million kilometers from Earth. At right, 2I/Borisov appears shortly after perihelion, its closest approach to Sun. European Southern Observatory observations indicate that this comet may never have passed close to any star before its 2019 perihelion passage. Borisov's closest approach to our fair planet, a distance of about 290 million kilometers, came on December 28, 2019. Even though Hubble's sharp images don't resolve the comet's nucleus, they did lead to estimates of less than 1 kilometer for its diameter.
Venus and the Triply Ultraviolet Sun (2022-03-06)

This was a very unusual type of solar eclipse.  Typically, it is the Earth's Moon that eclipses the Sun.  In 2012, though, the planet Venus took a turn.  Like a solar eclipse by the Moon, the phase of Venus became a continually thinner crescent as Venus became increasingly better aligned with the Sun.  Eventually the alignment became perfect and the phase of Venus dropped to zero.  The dark spot of Venus crossed our parent star.  The situation could technically be labeled a Venusian annular eclipse with an extraordinarily large ring of fire.  Pictured here during the occultation, the Sun was imaged in three colors of ultraviolet light by the Earth-orbiting Solar Dynamics Observatory, with the dark region toward the right corresponding to a coronal hole. Hours later, as Venus continued in its orbit, a slight crescent phase appeared again.  The next Venusian transit across the Sun will occur in 2117.
A Lion in Orion (2022-03-07)

Yes, but can you see the lion? A deep exposure shows the famous dark indentation that looks like a horse's head, visible just left and below center, and known unsurprisingly as the Horsehead Nebula.  The Horsehead Nebula (Barnard 33) is part of a vast complex of dark absorbing dust and bright glowing gas.  To bring out details of the  Horsehead's pasture, an astrophotographer artistically combined light accumulated for over 20 hours in hydrogen (orange), oxygen (blue), and sulfur (green). The resulting spectacular picture captured from Raachine, Lebanon, details an intricate tapestry of gaseous wisps and dust-laden filaments that were created and sculpted over eons by stellar winds and ancient supernovas.  The featured composition brings up another pareidolic animal icon -- that of a lion's head -- in the expansive orange colored gas above the horse's head.  The Flame Nebula is visible just to the left of the Horsehead.  The Horsehead Nebula lies 1,500 light years distant towards the constellation of Orion.

Image credit: Maroun Mahfoud
Moon in Inverted Colors (2022-03-08)

Which moon is this? It's Earth's moon -- but in inverted colors. Here, the pixel values corresponding to light and dark areas have been translated in reverse, or inverted, producing a false-color representation reminiscent of a black and white photographic negative.  However, this is an inverted color image -- where the muted colors of the moon are real but digitally exaggerated before inversion.  Normally bright rays from the large crater Tycho dominate the southern (bottom) features as easily followed dark green lines emanating from the 85-kilometer diameter impact site.  Normally dark lunar mare appear light and silvery.  The image was acquired in Southend-on-Sea, England, UK.  Historically, astronomical images recorded on photographic plates were directly examined on inverted-color negatives because it helped the eye pick out faint details.

Image credit: Dawid Glawdzin
A Flower-Shaped Rock on Mars (2022-03-09)

It is one of the more unusual rocks yet found on Mars. Smaller than a penny, the rock has several appendages that make it look, to some, like a flower. Although it would be a major discovery if the rock was truly a fossilized ancient Martian flower, there are less spectacular -- and currently preferred -- explanations for its unusual structure.  One theory that has emerged is that the rock is a type of concretion created by minerals deposited by water in cracks or divisions in existing rock. These concretions can be compacted together, can be harder and denser than surrounding rock, and can remain even after the surrounding rock erodes away.  The flower structure may also be caused by crystal clusters. The small rock, named Blackthorn Salt, has similarities to previously imaged Martian pebbles. The featured image was taken by the Curiosity rover on Mars in late February.  Scientists will continue to study data and images taken of this -- and similar -- surprising Martian rocks.    Review: Last Year in Space Pictures
Globular Star Cluster 47 Tuc (2022-03-10)

Globular star cluster 47 Tucanae is a jewel of the southern sky. Also known as NGC 104, it roams the halo of our Milky Way Galaxy along with some 200 other globular star clusters. The second brightest globular cluster (after Omega Centauri) as seen from planet Earth, 47 Tuc lies about 13,000 light-years away. It can be spotted with the naked-eye close on the sky to the Small Magellanic Cloud in the constellation of the Toucan. The dense cluster is made up of hundreds of thousands of stars in a volume only about 120 light-years across. Red giant stars on the outskirts of the cluster are easy to pick out as yellowish stars in this sharp telescopic portrait. Tightly packed globular cluster 47 Tuc is also home to a star with the closest known orbit around a black hole.

Image credit: Bernard Miller
When Rainbows Smile (2022-03-11)

Want to see a rainbow smile? Look near the zenith (straight up) when the sun is low in the sky and you might. This example of an ice halo known as a circumzenithal arc was captured above a palm tree top from Ragusa, Sicily on February 24. The vividly colorful arcs are often called smiling rainbows because of their upside down curvature and colors. For circumzenithal arcs the zenith is at the center and red is on the outside, compared to rainbows whose arcs bend toward the horizon after a downpour. True rainbows are formed by water droplets refracting the sunlight to produce a spectrum of colors, though. Circumzenithal arcs are the product of refraction and reflection in flat hexagonal ice crystals, like the ice crystals that create sundogs, formed in high thin clouds.

Image credit: Marcella Giulia Pace
Point Reyes Milky Way (2022-03-12)

Northern winter constellations and a long arc of the Milky Way are setting in this night skyscape looking toward the Pacific Ocean from Point Reyes on planet Earth's California coast. Sirius, alpha star of Canis Major, is prominent below the starry arc toward the left. Orion's yellowish Betelgeuse, Aldebaran in Taurus, and the blue tinted Pleiades star cluster also find themselves between Milky Way and northwestern horizon near the center of the scene. The nebulae visible in the series of exposures used to construct this panoramic view were captured in early March, but are just too faint to be seen with the unaided eye. On that northern night their expansive glow includes the reddish semi-circle of Barnard's Loop in Orion and NGC 1499 above and right of the Pleiades, also known as the California Nebula.

Image credit: Dan Zafra
Colorful Airglow Bands Surround Milky Way (2022-03-13)

Why would the sky glow like a giant repeating rainbow?  Airglow.  Now air glows all of the time, but it is usually hard to see. A disturbance however -- like an approaching storm -- may cause noticeable rippling in the Earth's atmosphere. These gravity waves are oscillations in air analogous to those created when a rock is thrown in calm water.  Red airglow likely originates from OH molecules about 87-kilometers high, excited by ultraviolet light from the Sun, while orange and green airglow is likely caused by sodium and oxygen atoms slightly higher up.  While driving near Keluke Lake in Qinghai Provence in China a few years ago, the photographer originally noticed mainly the impressive central band of the Milky Way Galaxy.  Stopping to photograph it, surprisingly, the resulting sensitive camera image showed airglow bands to be quite prominent and span the entire sky. The featured image has been digitally enhanced to make the colors more vibrant.

Image credit: Xiaohan Wang
Star Formation in the Eagle Nebula (2022-03-14)

Where do stars form?  One place, star forming regions known as "EGGs", are being uncovered at the end of this giant pillar of gas and dust in the Eagle Nebula (M16).  Short for evaporating gaseous globules, EGGs are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars.  Light from the hottest and brightest of these new stars heats the end of the pillar and causes further evaporation of gas and dust -- revealing yet more EGGs and more young stars.  This featured picture was created from exposures spanning over 30 hours with the Earth-orbiting Hubble Space Telescope in 2014, and digitally processed with modern software by experienced volunteers in Argentina. Newborn stars will gradually destroy their birth pillars over the next 100,000 years or so -- if a supernova doesn't destroy them first.
A Road to the Stars (2022-03-15)

Pictured -- a very scenic road to the stars.  The road approaches La Silla Observatory in Chile, with the ESO's 3.6-meter telescope just up ahead. To the left are some futuristic-looking support structures for the planned BlackGEM telescopes, an array of optical telescopes that will help locate optical counterparts to gravitational waves detections by LIGO and other detectors.  But there is much more. Red airglow illuminates the night sky on the right, while the central band of our Milky Way Galaxy slants across the image center. Jupiter can be seen just above the band near the image center, while Saturn is visible just above the 3.6-meter telescope dome. The two largest satellite galaxies of our Milky Way Galaxy, the LMC and SMC, are seen on the far right. The featured image panorama was built up from multiple 15-second exposures that were captured on 2019 June 30.  Two days later, La Silla experienced a rare total eclipse of the Sun.