juliensimon/nasa-apod huggingface dataset:
Shadows of Earth (2023-05-09)

Can you find two Earth shadows in today's image? It's a bit tricky. To find the first shadow, observe that the top part of the atmosphere appears pink and the lower part appears blue.  This is because the top half is exposed to direct sunlight, while the lower part is not. The purple area in between is known as the Belt of Venus, even though Venus can only appear on the other side of the sky, near the Sun. The blue color of the lower atmosphere is caused by the Earth blocking sunlight, creating Earth shadow number 1. Now, where is the second Earth shadow?  Take a look at the Moon.  Do you notice something unusual about the lower left part? That area appears unusually dark because it is in the shadow of the Earth, creating Earth shadow number 2. To be precise, the Moon was captured during a  lunar eclipse.  This carefully timed image was taken in Sampieri, Sicily, Italy, in July 2018.

Image credit: Marcella Giulia Pace
Milky Way over Egyptian Desert (2023-05-10)

For ten years the stargazer dreamed of taking a picture like this. The dreamer knew that the White Desert National Park in Egypt's Western Desert is a picturesque place hosting numerous chalk formations sculpted into surreal structures by a sandy wind. The dreamer knew that the sky above could be impressively dark on a clear moonless night, showing highlights such as the central band of our Milky Way Galaxy in impressive color and detail. So the dreamer invited an even more experienced astrophotographer to spend three weeks together in the desert and plan the composite images that needed to be taken and processed to create the dream image.  Over three days in mid-March, the base images were taken, all with the same camera and from the same location.  The impressive result is featured here, with the dreamer -- proudly wearing a traditional Bedouin galabyia -- pictured in the foreground.

Image credit: Amr Abdulwahab
Fomalhaut's Dusty Debris Disk (2023-05-11)

Fomalhaut is a bright star, a 25 light-year voyage from planet Earth in the direction of the constellation Piscis Austrinus. Astronomers first noticed Fomalhaut's excess infrared emission in the 1980s. Space and ground-based telescopes have since identified the infrared emission's source as a disk of dusty debris, evidence for a planetary system surrounding the hot, young star.  But this sharp infrared image from the James Webb Space Telescope's MIRI camera reveals details of Fomalhaut's debris disk never before seen, including a large dust cloud in the outer ring that is possible evidence for colliding bodies, and an inner dust disk and gap likely shaped and maintained by embedded but unseen planets. An image scale bar in au or astronomical units, the average Earth-Sun distance, appears at the lower left. Fomalhaut's outer circumstellar dust ring lies at about twice the distance of our own Solar System's Kuiper Belt of small icy bodies and debris beyond the orbit of Neptune.
Halley Dust, Mars Dust, and Milky Way (2023-05-12)

Grains of cosmic dust streaked through night skies in early May. Swept up as planet Earth plowed through the debris streams left behind by periodic Comet Halley, the annual meteor shower is known as the Eta Aquarids. This year, the Eta Aquarids peak was visually hampered by May's bright Full Moon, though. But early morning hours surrounding last May's shower of Halley dust were free of moonlight interference. In exposures recorded between April 28 and May 8 in 2022, this composited image shows nearly 90 Eta Aquarid meteors streaking from the shower's radiant in Aquarius over San Pedro de Atacama, Chile. The central Milky Way arcs above in the southern hemisphere's predawn skies. The faint band of light rising from the horizon is Zodiacal light, caused by dust scattering sunlight near our Solar System's ecliptic plane. Along the ecliptic and entrained in the Zodiacal glow are the bright planets Venus, Jupiter, Mars, and Saturn.  Of course Mars itself has recently been found to be a likely source of the dust along the ecliptic responsible for creating Zodiacal light.

Image credit: Petr Horalek
Apollo 17: The Crescent Earth (2023-05-13)

Our fair planet sports a curved, sunlit crescent against the black backdrop of space in this stunning photograph. From the unfamiliar perspective, the Earth is small and, like a telescopic image of a distant planet, the entire horizon is completely within the field of view. Enjoyed by crews on board the International Space Station, only much closer views of the planet are possible from low Earth orbit. Orbiting the planet once every 90 minutes, a spectacle of clouds, oceans, and continents scrolls beneath them with the partial arc of the planet's edge in the distance. But this digitally restored image presents a view so far only achieved by 24 humans, Apollo astronauts who traveled to the Moon and back again between 1968 and 1972. The original photograph, AS17-152-23420, was taken by the homeward bound crew of Apollo 17, on December 17, 1972. For now it is the last picture of Earth from this planetary perspective taken by human hands.
To Fly Free in Space (2023-05-14)

What would it be like to fly free in space?  At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was living the dream -- floating farther out than anyone had ever been before.  Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured, was floating free in space.   During Space Shuttle mission 41-B in 1984,  McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk". The MMU worked by shooting jets of nitrogen and was used to help deploy and retrieve satellites.  With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was later replaced with the SAFER backpack propulsion unit.
M16: Eagle Nebula Deep Field (2023-05-15)

From afar, the whole thing looks like an eagle.  A closer look at the Eagle Nebula, however, shows the bright region is actually a window into the center of a larger dark shell of dust.  Through this window, a brightly-lit workshop appears where a whole open cluster of stars is being formed.  In this cavity, tall pillars and round globules of dark dust and cold molecular gas remain where stars are still forming.  Already visible are several young bright blue stars whose light and winds are burning away and pushing back the remaining filaments and walls of gas and dust.  The Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with binoculars toward the constellation of the Serpent (Serpens).  This picture involved long and deep exposures and combined three specific emitted colors emitted by sulfur (colored as yellow), hydrogen (red), and oxygen (blue).

Image credit: Gianni Lacroce
Total Eclipse: The Big Corona (2023-05-16)

Most photographs don't adequately portray the magnificence of the Sun's corona. Seeing the corona first-hand during a total solar eclipse is unparalleled.  The human eye can adapt to see coronal features and extent that average cameras usually cannot. Welcome, however, to the digital age.  The featured image digitally combined short and long exposures taken in Exmouth, Australia that were processed to highlight faint and extended features in the corona during the total solar eclipse that occurred in April of 2023.  Clearly visible are intricate layers and glowing caustics of an ever changing mixture of hot gas and magnetic fields in the Sun's corona.  Looping prominences appear bright pink just past the Sun's edge.  Images taken seconds before and after the total eclipse show glimpses of the background Sun known as Baily's Beads and diamond ring effect.  The next total solar eclipse will cross North America in April of 2024.   Total Solar Eclipse of 2023 April Gallery: Notable Submissions to APOD

Image credit: Reinhold Wittich
Sunspot with Light Bridge (2023-05-17)

Why would a small part of the Sun appear slightly dark?  Visible is a close-up picture of sunspots, depressions on the Sun's surface that are slightly cooler and less bright than the rest of the Sun.  The Sun's complex magnetic field creates these cool regions by inhibiting hot material from entering the spots.  Sunspots can be larger than the Earth and typically last for about a week.  Part of active region AR 3297 crossing the Sun in early May, the large lower sunspot is spanned by an impressive light bridge of hot and suspended solar gas.  This high-resolution picture also shows clearly that the Sun's surface is a bubbling carpet of separate cells of hot gas. These cells are known as granules.  A solar granule is about 1000 kilometers across and lasts for only about 15 minutes.    Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)

Image credit: Mark Johnston
WR 134 Ring Nebula (2023-05-18)

Made with narrowband filters, this cosmic snapshot covers a field of view about the size of the full Moon within the boundaries of the constellation Cygnus. It highlights the bright edge of a ring-like nebula traced by the glow of ionized sulfur, hydrogen, and oxygen gas. Embedded in the region's interstellar clouds of gas and dust, the complex, glowing arcs are sections of bubbles or shells of material swept up by the wind from Wolf-Rayet star WR 134, brightest star near the center of the frame. Distance estimates put WR 134 about 6,000 light-years away, making the frame over 50 light-years across. Shedding their outer envelopes in powerful stellar winds, massive Wolf-Rayet stars have burned through their nuclear fuel at a prodigious rate and end this final phase of massive star evolution in a spectacular supernova explosion. The stellar winds and final supernovae enrich the interstellar material with heavy elements to be incorporated in future generations of stars.

Image credit: Craig Stocks
Curly Spiral Galaxy M63 (2023-05-19)

A bright spiral galaxy of the northern sky, Messier 63 is nearby, about 30 million light-years distant toward the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across, about the size of our own Milky Way. Its bright core and majestic spiral arms lend the galaxy its popular name, The Sunflower Galaxy. This exceptionally deep exposure also follows faint, arcing star streams far into the galaxy's halo. Extending nearly 180,000 light-years from the galactic center, the star streams are likely remnants of tidally disrupted satellites of M63. Other satellite galaxies of M63 can be spotted in the remarkable wide-field image, including faint dwarf galaxies, which could contribute to M63's star streams in the next few billion years.

Image credit: Sophie Paulin
Galileo's Europa (2023-05-20)

Looping through the Jovian system in the late 1990s, the Galileo spacecraft recorded stunning views of Europa and uncovered evidence that the moon's icy surface likely hides a deep, global ocean. Galileo's Europa image data has been remastered here, with improved calibrations to produce a color image approximating what the human eye might see. Europa's long curving fractures hint at the subsurface liquid water.  The tidal flexing the large moon experiences in its elliptical orbit around Jupiter supplies the energy to keep the ocean liquid. But more tantalizing is the possibility that even in the absence of sunlight that process could also supply the energy to support life, making Europa one of the best places to look for life beyond Earth. What kind of life could thrive in a deep, dark, subsurface ocean? Consider planet Earth's own extreme shrimp.
Tardigrade in Moss (2023-05-21)

Is this an alien?  Probably not, but of all the animals on Earth, the tardigrade might be the best candidate. That's because tardigrades are known to be able to go for decades without food or water, to survive temperatures from near absolute zero to well above the boiling point of water, to survive pressures from near zero to well above that on ocean floors, and to survive direct exposure to dangerous radiations.  The far-ranging survivability of these extremophiles was tested in 2011 outside an orbiting space shuttle. Tardigrades are so durable partly because they can repair their own DNA and reduce their body water content to a few percent. Some of these miniature water-bears almost became  extraterrestrials in 2011 when they were launched toward to the Martian moon Phobos, and again in 2021 when they were launched toward Earth's own moon, but the former launch failed, and the latter landing crashed. Tardigrades are more common than humans across most of the Earth. Pictured here in a color-enhanced electron micrograph, a millimeter-long tardigrade crawls on moss.   Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)

Image credit: Nicole Ottawa & Oliver Meckes / Eye of Science / 
Science Source Images
Supernova Discovered in Nearby Spiral Galaxy M101 (2023-05-22)

A nearby star has exploded and humanity's telescopes are turning to monitor it.  The supernova, dubbed SN 2023ixf, was discovered by Japanese astronomer Koichi Itagaki three days ago and subsequently located on automated images from the Zwicky Transient Facility two days earlier.  SN 2023ixf occurred in the photogenic Pinwheel Galaxy M101, which, being only about 21 million light years away, makes it the closest supernova seen in the past five years, the second closest in the past 10 years, and the second supernova found in M101 in the past 15 years.  Rapid follow up observations already indicate that SN 2023ixf is a Type II supernova, an explosion that occurs after a massive star runs out of nuclear fuel and collapses.  The featured image shows home spiral galaxy two days ago with the supernova highlighted, while the roll-over image shows the same galaxy a month before. SN 2023ixf will likely brighten and remain visible to telescopes for months.  Studying such a close and young Type II supernova may yield new clues about massive stars and how they explode.

Image credit: Craig Stocks
Jupiter's Swirls from Juno (2023-05-23)

Big storms are different on Jupiter. On Earth, huge hurricanes and colossal cyclones are centered on regions of low pressure, but on Jupiter, it is the high-pressure, anti-cyclone storms that are the largest. On Earth, large storms can last weeks, but on Jupiter they can last years. On Earth, large storms can be as large as a country, but on Jupiter, large storms can be as large as planet Earth. Both types of storms are known to exhibit lightning. The featured image of Jupiter's clouds was composed from images and data captured by the robotic Juno spacecraft as it swooped close to the massive planet in August 2020.  A swirling white oval is visible nearby, while numerous smaller cloud swirls extend into the distance.  On Jupiter, light-colored clouds are usually higher up than dark clouds. Despite their differences, studying storm clouds on distant Jupiter provides insights into storms and other weather patterns on familiar Earth.     Surf the Universe: Random APOD Generator
Observatory Aligned with Moon Occulting Jupiter (2023-05-24)

Sometimes we witness the Moon moving directly in front of -- called occulting -- one of the planets in our Solar System. Earlier this month that planet was Jupiter.  Captured here was the moment when Jupiter re-appeared from behind the surface of our Moon. The Moon was in its third quarter, two days before the dark New Moon. Now, our Moon is continuously half lit by the Sun, but when in its third quarter, relatively little of that half can be seen from the Earth. Pictured, the Moon itself was aligned behind the famous Lick Observatory in California, USA, on the summit of Mount Hamilton. Coincidentally, Lick enabled the discovery of a moon of Jupiter: Amalthea, the last visually detected moon of Jupiter after Galileo's observations.   Gallery: Moon Occults Jupiter in 2023 May: Notable Submissions to APOD

Image credit: Rick Whitacre;
Text: Natalia Lewandowska 
(SUNY Oswego)
Cat's Eye Wide and Deep (2023-05-25)

The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its more familiar outlines are seen in the brighter central region of the nebula in this impressive wide-angle view. But this wide and deep image combining data from two telescopes also reveals its extremely faint outer halo. At an estimated distance of 3,000 light-years, the faint outer halo is over 5 light-years across. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. More recently, some planetary nebulae are found to have halos like this one, likely formed of material shrugged off during earlier episodes in the star's evolution. While the planetary nebula phase is thought to last for around 10,000 years, astronomers estimate the age of the outer filamentary portions of this halo to be 50,000 to 90,000 years. Visible on the right, some 50 million light-years beyond the watchful planetary nebula, lies spiral galaxy NGC 6552.

Image credit: Jean-François Bax
Virgo Cluster Galaxies (2023-05-26)

Galaxies of the Virgo Cluster are scattered across this nearly 4 degree wide telescopic field of view. About 50 million light-years distant, the Virgo Cluster is the closest large galaxy cluster to our own local galaxy group. Prominent here are Virgo's bright elliptical galaxies Messier catalog, M87 at bottom center, and M84 and M86 (top to bottom) near top left. M84 and M86 are recognized as part of Markarian's Chain, a visually striking line-up of galaxies on the left side of this frame. Near the middle of the chain lies an intriguing interacting pair of galaxies, NGC 4438 and NGC 4435, known to some as Markarian's Eyes. Of course giant elliptical galaxy M87 dominates the Virgo cluster. It's the home of a super massive black hole, the first black hole ever imaged by planet Earth's Event Horizon Telescope.

Image credit: Abdullah Alharbi
Crescent Neptune and Triton (2023-05-27)

Gliding through the outer Solar System, in 1989 the Voyager 2 spacecraft looked toward the Sun to find this view of most distant planet Neptune and its moon Triton together in a crescent phase.  The elegant image of ice-giant planet and largest moon was taken from behind just after Voyager's closest approach. It could not have been taken from Earth because the most distant planet never shows a crescent phase to sunward eyes. Heading for the heliopause and beyond, the spacecraft's parting vantage point also robs Neptune of its familiar blue hue.
Ida and Dactyl: Asteroid and Moon (2023-05-28)

This asteroid has a moon.  The robot spacecraft Galileo on route to Jupiter in 1993 encountered and photographed two asteroids during its long interplanetary voyage.  The second minor planet it photographed, 243 Ida, was unexpectedly discovered to have a moon. The tiny moon, Dactyl, is only about 1.6 kilometers across and seen as a small dot on the right of the sharpened featured image.  In contrast, the potato-shaped Ida is much larger, measuring about 60 kilometers long and 25 km wide.  Dactyl is the first moon of an asteroid ever discovered -- now many asteroids are known to have moons. The names Ida and Dactyl are from Greek mythology.
Milky Way over a Turquoise Wonderland (2023-05-29)

What glows there?  The answer depends: sea or sky? In the sea, the unusual blue glow is bioluminescence. Specifically, the glimmer arises from Noctiluca scintillans, single-celled plankton stimulated by the lapping waves. The plankton use their glow to startle and illuminate predators.  This mid-February display on an island in the Maldives was so intense that the astrophotographer described it as a turquoise wonderland. In the sky, by contrast, are the more familiar glows of stars and nebulas. The white band rising from the artificially-illuminated green plants is created by billions of stars in the central disk of our Milky Way Galaxy.  Also visible in the sky is the star cluster Omega Centauri, toward the left, and the famous Southern Cross asterism in the center. Red-glowing nebulas include the bright Carina Nebula, just right of center, and the expansive Gum Nebula on the upper right.

Image credit: Petr Horálek /
Institute of Physics in Opava,
Sovena Jani
M27: The Dumbbell Nebula (2023-05-30)

Is this what will become of our Sun? Quite possibly.  The first hint of our Sun's future was discovered inadvertently in 1764. At that time, Charles Messier was compiling a list of diffuse objects not to be confused with comets. The 27th object on Messier's list, now known as M27 or the Dumbbell Nebula, is a planetary nebula, one of the brightest planetary nebulae on the sky and visible with binoculars toward the constellation of the Fox (Vulpecula). It takes light about 1000 years to reach us from M27, featured here in colors emitted by sulfur (red), hydrogen (green) and oxygen (blue). We now know that in about 6 billion years, our Sun will shed its outer gases into a planetary nebula like M27, while its remaining center will become an X-ray hot white dwarf star.  Understanding the physics and significance of M27 was well beyond 18th century science, though. Even today, many things remain mysterious about planetary nebulas, including how their intricate shapes are created.

Image credit: Patrick A. Cosgrove
Simulation: A Disk Galaxy Forms (2023-05-31)

How did we get here? We know that we live on a planet orbiting a star orbiting a galaxy, but how did all of this form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. Specifically, this featured video from the IllustrisTNG collaboration tracks gas from the early universe (redshift 12) until today (redshift 0). As the simulation begins, ambient gas falls into and accumulates in a region of relatively high gravity.  After a few billion years, a well-defined center materializes from a strange and fascinating cosmic dance. Gas blobs -- some representing small satellite galaxies -- continue to fall into and become absorbed by the rotating galaxy as the present epoch is reached and the video ends.  For the Milky Way Galaxy, however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy will collide and coalesce with the slightly larger Andromeda spiral disk galaxy in the next few billion years.    Open Science: Browse 3,000+ codes in the Astrophysics Source Code Library
Recycling Cassiopeia A (2023-06-01)

Massive stars in our Milky Way Galaxy live spectacular lives.  Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After a few million years, the enriched material is blasted back into interstellar space where star formation can begin anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle. Light from the explosion which created this supernova remnant would have been first seen in planet Earth's sky about 350 years ago, although it took that light about 11,000 years to reach us. This false-color image, composed of X-ray and optical image data from the Chandra X-ray Observatory and Hubble Space Telescope, shows the still hot filaments and knots in the remnant. It spans about 30 light-years at the estimated distance of Cassiopeia A. High-energy X-ray emission from specific elements has been color coded, silicon in red, sulfur in yellow, calcium in green and iron in purple, to help astronomers explore the recycling of our galaxy's star stuff. Still expanding, the outer blast wave is seen in blue hues. The bright speck near the center is a neutron star, the incredibly dense, collapsed remains of the massive stellar core.