juliensimon/nasa-apod huggingface dataset:
The Porpoise Galaxy from Hubble (2020-05-10)

What's happening to this spiral galaxy? Just a few hundred million years ago, NGC 2936, the upper of the two large galaxies shown, was likely a normal spiral galaxy -- spinning, creating stars -- and minding its own business. But then it got too close to the massive elliptical galaxy NGC 2937 below and took a dive. Dubbed the Porpoise Galaxy for its iconic shape, NGC 2936 is not only being deflected but also being distorted by the close gravitational interaction. A burst of young blue stars forms the nose of the porpoise toward the right of the upper galaxy, while the center of the spiral appears as an eye.  Alternatively, the galaxy pair, together known as Arp 142, look to some like a penguin protecting an egg. Either way, intricate dark dust lanes and bright blue star streams trail the troubled galaxy to the lower right. The featured re-processed image showing Arp 142 in unprecedented detail was taken by the Hubble Space Telescope last year. Arp 142 lies about 300 million light years away toward the constellation, coincidently, of the Water Snake (Hydra). In a billion years or so the two galaxies will likely merge into one larger galaxy.

Image credit: Raul Villaverde
Behind Betelgeuse (2020-05-11)

What's behind Betelgeuse? One of the brighter and more unusual stars in the sky, the red supergiant star Betelgeuse can be found in the direction of famous constellation Orion. Betelgeuse, however, is actually well in front of many of the constellation's other bright stars, and also in front of the greater Orion Molecular Cloud Complex.  Numerically, light takes about 700 years to reach us from Betelgeuse, but about 1,300 years to reach us from the Orion Nebula and its surrounding dust and gas.  All but the largest telescopes see Betelgeuse as only a point of light, but a point so bright that the inherent blurriness created by the telescope and Earth's atmosphere make it seem extended.  In the featured long-exposure image, thousands of stars in our Milky Way Galaxy can be seen in the background behind Betelgeuse, as well as dark dust from the Orion Molecular Cloud, and some red-glowing emission from hydrogen gas on the outskirts of the more distant Lambda Orionis Ring. Betelgeuse has recovered from appearing unusually dim over the past six months, but is still expected to explode in a spectacular supernova sometime in the next (about) 100,000 years.

Image credit: Adam Block,
Steward Observatory,
University of Arizona
Lyrid Meteors from the Constellation Lyra (2020-05-12)

Where are all of these meteors coming from?  In terms of direction on the sky, the pointed answer is the constellation of Small Harp (Lyra).  That is why the famous meteor shower that peaks every April is known as the Lyrids -- the meteors all appear to came from a radiant toward Lyra. In terms of parent body, though, the sand-sized debris that makes up the Lyrid meteors come from Comet Thatcher. The comet follows a well-defined orbit around our Sun, and the part of the orbit that approaches Earth is superposed in front of Lyra. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Lyra. Featured here, a composite image containing over 33 meteors (can you find them all?) from last month's  Lyrid meteor shower shows several bright meteors that streaked over a shore of Seč Lake in the Czech Republic. Also visible are the bright stars Vega and Altair, the planet Jupiter, and the central band of our Milky Way Galaxy.   Notable APOD Submissions: Lyrid Meteor Shower 2020

Image credit: Petr Horálek
Jupiter in Infrared from Gemini (2020-05-13)

In infrared, Jupiter lights up the night.  Recently, astronomers at the Gemini North Observatory in Hawaii, USA, created some of the best infrared photos of Jupiter ever taken from Earth’s surface, pictured.  Gemini was able to produce such a clear image using a technique called lucky imaging, by taking many images and combining only the clearest ones that, by chance, were taken when Earth's atmosphere was the most calm.  Jupiter’s jack-o’-lantern-like appearance is caused by the planet’s different layers of clouds.  Infrared light can pass through clouds better than visible light, allowing us to see deeper, hotter layers of Jupiter's atmosphere, while the thickest clouds appear dark.  These pictures, together with ones from the Hubble Space Telescope and the Juno spacecraft, can tell us a lot about weather patterns on Jupiter, like where its massive, planet-sized storms form.   Notable APOD Submissions: Flower Moon 2020
Comet Halley vs Comet SWAN (2020-05-14)

The pre-dawn hours of May 3rd were moonless as grains of cosmic dust streaked through southern skies above Reunion Island. Swept up as planet Earth plowed through dusty debris streams left behind periodic Comet 1/P Halley, the annual meteor shower is known as the Eta Aquarids. This inspired exposure captures a bright aquarid meteor flashing left to right over a sea of clouds. The meteor streak points back to the shower's radiant in the constellation Aquarius, well above the eastern horizon and off the top of the frame. Known for speed Eta Aquarid meteors move fast, entering the atmosphere at about 66 kilometers per second, visible at altitudes of 100 kilometers or so. Then about 6 light-minutes from Earth, the pale greenish coma and long tail of Comet C/2020 F8 SWAN were not to be left out of the celestial scene, posing above the volcanic peaks left of center. Now in the northern sky's morning twilight near the eastern horizon Comet SWAN has not become as bright as anticipated though. This first time comet made its closest approach to planet Earth only two days ago and reaches perihelion on May 27.

Image credit: Luc Perrot
Galaxy Wars: M81 and M82 (2020-05-15)

These two galaxies are far far away, 12 million light-years distant toward the northern constellation of the Great Bear. On the left, with grand spiral arms and bright yellow core is spiral galaxy M81, some 100,000 light-years across.  On the right marked by red gas and dust clouds, is irregular galaxy M82.  The pair have been locked in gravitational combat for a billion years. Gravity from each galaxy has profoundly affected the other during a series of cosmic close encounters.  Their last go-round lasted about 100 million years and likely raised density waves rippling around M81, resulting in the richness of M81's spiral arms.  M82 was left with violent star forming regions and colliding gas clouds so energetic the galaxy glows in X-rays.  In the next few billion years, their continuing gravitational encounters will result in a merger, and a single galaxy will remain.

Image credit: Dietmar Hager
The Dark River to Antares (2020-05-16)

A dark river seems to flow through this sky from the horizon toward colorful clouds near red giant star Antares. Murky looking, the dark river is a dusty nebula obscuring background starlight near the central Milky Way, although the dark dust nebula contains mostly hydrogen molecular gas.  Dust scattering starlight around Antares, alpha star of Scorpius, creates the unusual yellow-hued reflection nebula. Above it, bright blue double star Rho Ophiuchi is embedded in more typical dusty bluish reflection nebulae, with red emission nebulae also scattered through the interstellar space. Globular star cluster M4 looks almost like a bright star just above and right of Antares, though it lies far behind the colorful clouds, at a distance of some 7,000 light-years. The dark river itself is about 500 light years away.  To create the startling night sky view, all background and foreground exposures were made back to back with the same camera and telephoto lens on the same night from the same location. In combination they produce a stunning image that reveals a range of brightness and color that your eye can't quite perceive. Recorded in the early hours of January 31, the composite also captures Mars still near the eastern horizon and rising to join rival Antares on the celestial stage. Bright Mars and its watery reflection are left of a lonely tree in the Bosque del Apache National Wildlife Refuge, New Mexico, planet Earth.

Image credit: Paul Schmit
A Waterspout in Florida (2020-05-17)

What's happening over the water?  Pictured here is one of the better images yet recorded of a waterspout, a type of tornado that occurs over water.  Waterspouts are spinning columns of rising moist air that typically form over warm water. Waterspouts can be as dangerous as tornadoes and can feature wind speeds over 200 kilometers per hour.  Some waterspouts form away from thunderstorms and even during relatively fair weather.  Waterspouts may be relatively transparent and initially visible only by an unusual pattern they create on the water.  The featured image was taken in 2013 July near Tampa Bay, Florida. The Atlantic Ocean off the coast of Florida is arguably the most active area in the world for waterspouts, with hundreds forming each year.    Experts Debate: How will humanity first discover extraterrestrial life?

Image credit: Joey Mole
Journey into the Cosmic Reef (2020-05-18)

What would you see if you could fly into the Cosmic Reef? The nebular cloud NGC 2014 appear to some like an ocean reef that resides in the sky, specifically in the LMC, the largest satellite galaxy of our Milky Way Galaxy. A detailed image of this distant nebula was taken by the Hubble Space Telescope to help commemorate 30 years of investigating the cosmos.  Data and images of this cosmic reef have been combined into the three-dimensional model flown through in the featured video.  The computer animated sequence first takes you past a star cluster highlighted by bright blue stars, below pillars of gas and dust slowly being destroyed by the energetic light and winds emitted by these massive stars.  Filaments of gas and dust are everywhere, glowing in the red light of hydrogen and nitrogen. The animation next takes you to the blue-colored nebula NGC 2020, glowing in light emitted by oxygen and surrounding a Wolf-Rayet star about 200,000 times brighter than our Sun -- a nebula thought to be the ejected outer atmosphere of this stellar monster.  As the animation concludes, the virtual camera pivots to show that NGC 2020 has a familiar hourglass shape when viewed from the side.    Follow APOD on Instagram in: English, Indonesian, Persian, or Portuguese
Posters of the Solar System (2020-05-19)

Would you like a NASA astronomy-exploration poster?  You are just one page-print away. Any of the panels you see on the featured image can appear on your wall.  Moreover, this NASA page has, typically, several more posters of each of the Solar System objects depicted.  These posters highlight many of the places humanity, through NASA, has explored in the past 50 years, including our Sun, and planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Moons of Jupiter that have been posterized include Europa, Ganymede, Callisto, and Io, while moons of Saturn that can be framed include Enceladus and Titan.  Images of Pluto, Ceres, comets and asteroids are also presented, while six deep space scenes -- well beyond our Solar System -- can also be prominently displayed.  If you lack wall space or blank poster sheets don't despair -- you can still print many of these out as trading cards.
Moon, Mars, Saturn, Jupiter, Milky Way (2020-05-20)

It is not a coincidence that planets line up. That's because all of the planets orbit the Sun in (nearly) a single sheet called the plane of the ecliptic. When viewed from inside that plane -- as Earth dwellers are likely to do -- the planets all appear confined to a single band. It is a coincidence, though, when three of the brightest planets all appear in nearly the same direction.  Such a coincidence was captured about a month ago. Featured above, Earth's Moon, Mars, Saturn, and Jupiter were all imaged together, just before sunrise, from the Black Sea coast of Bulgaria.  A second band is visible diagonally across this image -- the central band of our Milky Way Galaxy. If you wake up early, you will find that these same planets remain visible in the morning sky this month, too.   Astrophysicists: Browse 2,100+ codes in the Astrophysics Source Code Library

Image credit: Mihail Minkov
Phases of Venus (2020-05-21)

Just as the Moon goes through phases, Venus' visible sunlit hemisphere waxes and wanes. This composite of backyard telescopic images illustrates the steady changes for Venus during its current stint as our evening star, as the inner planet grows larger but narrows to a thin crescent. Images from bottom to top were taken during 2020 on dates February 27, March 20, April 14, April 24, May 8, and May 14. Gliding along its interior orbit between Earth and Sun, Venus grows larger during that period because it is approaching planet Earth. Its crescent narrows, though, as Venus swings closer to our line-of-sight to the Sun. Closest to the Earth-Sun line but passing about 1/2 degree north of the Sun on June 3, Venus will reach a (non-judgmental) inferior conjunction. Soon after, Venus will shine clearly above the eastern horizon in predawn skies as planet Earth's morning star. After sunset tonight look for Venus above the western horizon and you can also spot elusive innermost planet Mercury.

Image credit: Richard Addis
South of Carina (2020-05-22)

With natal dust clouds in silhouette against glowing atomic gas, this colorful and chaotic vista lies within one of the largest star forming regions in the Milky Way galaxy, the Great Carina Nebula. The telescopic close-up frames a field of view about 80 light-years across, a little south and east of Eta Carinae, the nebula's most energetic and enigmatic star. Captured under suburban skies improved during national restrictions, a composite of narrowband image data was used to create the final image. In it, characteristic emission from the nebula's ionized sulfur, hydrogen, and oxygen atoms is mapped to red, green, and blue hues, a color palette also popular in Hubble Space Telescope images. The celestial landscape of bright ridges of emission bordered by cool, obscuring dust lies about 7,500 light-years away toward the southern constellation Carina.

Image credit: Ignacio Diaz Bobillo
Ghost Fungus to Magellanic Cloud (2020-05-23)

Stars shine and satellites glint in this clear, dark, night sky over Wannon Falls Reserve, South West Victoria, Australia. In fact the fuzzy, faint apparition above the tree tops is the only cloud visible, also known as the Large Magellanic Cloud, satellite galaxy of our own Milky Way. In the foreground, an Omphalotus nidiformis (ghost fungus) from planet Earth shines with a surprisingly bright bioluminescence. Like the Magellanic cloud, the ghost fungus was easily seen with the eye. Its ghostly glow was actually a dull green, but it appears bright green in digital camera picture. Two images were blended to create the scene. One focused on the distant stars and Large Magellanic Cloud some 160,000 light-years away. Another was focused on the foreground and glowing fungus several light-nanoseconds from the camera lens.

Image credit: Gill Fry
Valles Marineris: The Grand Canyon of Mars (2020-05-24)

The largest canyon in the Solar System cuts a wide swath across the face of Mars.  Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep.  By comparison, the Earth's Grand Canyon in Arizona, USA is 800 kilometers long, 30 kilometers across, and 1.8 kilometers deep.  The origin of the Valles Marineris remains unknown, although a leading hypothesis holds that it started as a crack billions of years ago as the planet cooled.  Several geologic processes have been identified in the canyon.  The featured mosaic was  created from over 100 images of Mars taken by Viking Orbiters in the 1970s.
Mystic Mountain Monster being Destroyed (2020-05-25)

Inside the head of this interstellar monster is a star that is slowly destroying it.  The huge monster, actually an inanimate series of pillars of gas and dust, measures light years in length.  The in-head star is not itself visible through the opaque interstellar dust but is bursting out partly by ejecting opposing beams of energetic particles called Herbig-Haro jets.  Located about 7,500 light years away in the Carina Nebula and known informally as Mystic Mountain, the appearance of these pillars is dominated by dark dust even though they are composed mostly of clear hydrogen gas.  The featured image was taken with the Hubble Space Telescope. All over these pillars, the energetic light and winds from massive newly formed stars are evaporating and dispersing the dusty stellar nurseries in which they formed.  Within a few million years, the head of this giant, as well as most of its body, will have been completely evaporated by internal and surrounding stars.    APOD across world languages: Arabic, Catalan, Chinese (Beijing), Chinese (Taiwan), Croatian, Czech, Dutch, Farsi, French, French, German, Hebrew, Indonesian, Japanese, Korean, Montenegrin, Polish, Russian, Serbian, Slovenian,  Spanish and Ukrainian
The Milky Way over Snow-Capped Himalayas (2020-05-26)

What’s higher than the Himalayas? Although the Himalayan Mountains are the tallest on planet Earth, they don't measure up to the Milky Way. Visible above the snow-capped mountains in the featured image is the arcing central band of our home galaxy.  The bright spot just above the central plane is the planet Jupiter, while the brightest orange spot on the upper right is the star Antares.  The astrophotographer braved below-zero temperatures at nearly 4,000-meters altitude to take the photographs that compose this image.  The featured picture is a composite of eight exposures taken with same camera and from the same location over three hours, just after sunset, in 2019 April, from near Bimtang Lake in Nepal.  Over much of planet Earth, the planets Mercury (faint) and Venus (bright) will be visible this week after sunset.   Experts Debate: How will humanity first discover extraterrestrial life?

Image credit: Tomas
Havel
Earth and Moon through Saturn's Rings (2020-05-27)

What are those dots between Saturn's rings? Our Earth and Moon. Just over three years ago, because the Sun was temporarily blocked by the body of Saturn, the robotic Cassini spacecraft was able to look toward the inner Solar System. There, it spotted our Earth and Moon -- just pin-pricks of light lying about 1.4 billion kilometers distant. Toward the right of the featured image is Saturn's A ring, with the broad Encke Gap on the far right and the narrower Keeler Gap toward the center.  On the far left is Saturn's continually changing F Ring.  From this perspective, the light seen from Saturn's rings was scattered mostly forward , and so appeared backlit.  After more than a decade of exploration and discovery, the Cassini spacecraft ran low on fuel in 2017 and was directed to enter Saturn's atmosphere, where it surely melted.   Gallery: Notable Venus & Mercury Conjunction 2020 Images submitted to APOD
Reflecting the International Space Station (2020-05-28)

Still bathed in sunlight, the International Space Station arced through the evening sky over lake Wulfsahl-Gusborn in northern Germany, just after sunset on March 25. The familiar constellation of Orion can be seen left of the trail of the orbital station's bright passage. On the right, Venus is the brilliant evening star above the western horizon. With the camera fixed to a tripod, this scene was captured in a series of five exposures. How can you tell? The short time delay between the end of one exposure and the beginning of the next leaves small gaps in the ISS light trail. Look closely and you'll also see that the sky that appears to be above the horizon is actually a reflection though. The final image has been vertically inverted and the night skyscape recorded in the mirror-like waters of the small lake.

Image credit: Helmut Schnieder
Mercury Meets Crescent Venus (2020-05-29)

That's not a bright star and crescent Moon caught between branches of a eucalyptus tree. It's Venus in a crescent phase and Mercury. Near the western horizon after sunset, the two inner planets closely shared this telescopic field of view on May 22, seen from a balcony in Civitavecchia, Italy. Venus, the very bright celestial beacon, is wandering lower into the evening twilight. It grows larger in apparent size and shows a thinner crescent as it heads toward its inferior conjunction, positioned between Earth and Sun on June 3. Mercury, in a fuller phase, is climbing in the western sky though, reaching its maximum angular distance from the Sun on June 4 Still, this remarkably close pairing with brilliant Venus made Mercury, usually lost in bright twilight skies, easier to spot from planet Earth.   Gallery: Notable Venus & Mercury Conjunction 2020 Images submitted to APOD

Image credit: Marco Meniero
Green Flashes: Sun, Moon, Venus, Mercury (2020-05-30)

Follow a sunset on a clear day against a distant horizon and you might glimpse green just as the Sun disappears from view. The green flash is caused by refraction of light rays traveling to the eye over a long path through the atmosphere. Shorter wavelengths refract more strongly than longer redder wavelengths and the separation of colors lends a green hue to the last visible vestige of the solar disk. It's harder to see a green flash from the Moon, not to mention the diminutive disks of Venus and Mercury. But a telescope or telephoto lens and camera can help catch this tantalizing result of atmospheric refraction when the celestial bodies are near the horizon. From Sicily, the top panels were recorded on March 18, 2019 for the Sun and May 8, 2020 for the Moon. Also from the Mediterranean island, the bottom panels were shot during the twilight apparition of Venus and Mercury near the western horizon on May 24.

Image credit: Marcella Giulia Pace
Aurora over Sweden (2020-05-31)

It was bright and green and stretched across the sky. This striking aurora display was captured in 2016 just outside of Östersund, Sweden. Six photographic fields were merged to create the featured panorama spanning almost 180 degrees.  Particularly striking aspects of this aurora include its sweeping arc-like shape and its stark definition.  Lake Storsjön is seen in the foreground, while several familiar constellations and the star Polaris are visible through the aurora, far in the background.  Coincidently, the aurora appears to avoid the Moon visible on the lower left.  The aurora appeared a day after a large hole opened in the Sun's corona allowing particularly energetic particles to flow out into the Solar System.  The green color of the aurora is caused by oxygen atoms recombining with ambient electrons high in the Earth's atmosphere.

Image credit: Göran Strand
The Lively Center of the Lagoon Nebula (2020-06-01)

The center of the Lagoon Nebula is a whirlwind of spectacular star formation. Visible near the image center, at least two long funnel-shaped clouds, each roughly half a light-year long, have been formed by extreme stellar winds and intense energetic starlight.  A tremendously bright nearby star, Herschel 36, lights the area.  Vast walls of dust hide and redden other hot young stars.  As energy from these stars pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds which may cause the funnels.  This picture, spanning about 15 light years, features two colors detected by the orbiting Hubble Space Telescope.  The Lagoon Nebula, also known as M8, lies about 5000 light years distant toward the constellation of the Archer Sagittarius.