juliensimon/nasa-apod huggingface dataset:
Mercury's Vivaldi Crater from BepiColombo (2024-09-16)

Why does this large crater on Mercury have two rings and a smooth floor?  No one is sure.  The unusual feature called Vivaldi Crater spans 215 kilometers and was imaged again in great detail by ESA's and JAXA's robotic BepiColombo spacecraft on a flyby earlier this month. A large circular feature on a rocky planet or moon is usually caused by either an impact by a small asteroid or a comet fragment, or a volcanic eruption. In the case of Vivaldi, it is possible that both occurred -- a heavy strike that caused a smooth internal lava flow.  Double-ringed craters are rare, and the cause of the inner rings remains a topic of research.  The speed-slowing gravity-assisted flyby of Mercury by BepiColombo was in preparation for the spacecraft entering orbit around the Solar System's innermost planet in 2026.
Melotte 15 in the Heart Nebula (2024-09-17)

Cosmic clouds form fantastic shapes in the central regions of emission nebula IC 1805. The clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster, Melotte 15. About 1.5 million years young, the cluster stars are scattered in this colorful skyscape, along with dark dust clouds in silhouette against glowing atomic gas. A composite of narrowband and broadband telescopic images, the view spans about 15 light-years and includes emission from ionized hydrogen, sulfur, and oxygen atoms mapped to green, red, and blue hues in the popular Hubble Palette. Wider field images reveal that IC 1805's simpler, overall outline suggests its popular name - the Heart Nebula. IC 1805 is located about 7,500 light years away toward the boastful constellation Cassiopeia.

Image credit: Richard McInnis
The Mermaid Nebula Supernova Remnant (2024-09-18)

New stars are born from the remnants of dead stars. The gaseous remnant of the gravitational collapse and subsequent death of a very massive star in our Milky Way created the G296.5+10.0 supernova remnant, of which the featured Mermaid Nebula is part. Also known as the Betta Fish Nebula, the Mermaid Nebula makes up part of an unusual subclass of supernova remnants that are two-sided and nearly circular. Originally discovered in X-rays, the filamentary nebula is a frequently studied source also in radio and gamma-ray light.  The blue color visible here originates from doubly ionized oxygen (OIII), while the deep red is emitted by hydrogen gas. The nebula's mermaid-like shape has proven to be useful for measurements of the interstellar magnetic field.   Growing Gallery: Last night's supermoon eclipse

Image credit: Neil Corke; 
Text: Natalia Lewandowska 
(SUNY Oswego)
The Dark Seahorse of Cepheus (2024-09-19)

Spanning light-years, this suggestive shape known as the Seahorse Nebula floats in silhouette against a rich, luminous background of stars. Seen toward the royal northern constellation of Cepheus, the dusty, dark nebula is part of a Milky Way molecular cloud some 1,200 light-years distant. It is also listed as Barnard 150 (B150), one of 182 dark markings of the sky cataloged in the early 20th century by astronomer E. E. Barnard. Packs of low mass stars are forming within, but their collapsing cores are only visible at long infrared wavelengths. Still, the colorful Milky Way stars of Cepheus add to this stunning galactic skyscape.   Growing Gallery: This week's supermoon eclipse

Image credit: Davide Broise
A Hazy Harvest Moon (2024-09-20)

For northern hemisphere dwellers, September's Full Moon was the Harvest Moon. On September 17/18 the sunlit lunar nearside passed into shadow, just grazing Earth's umbra, the planet's dark, central shadow cone, in a partial lunar eclipse. Over the two and a half hours before dawn a camera fixed to a tripod was used to record this series of exposures as the eclipsed Harvest Moon set behind Spiš Castle in the hazy morning sky over eastern Slovakia. Famed in festival, story, and song, Harvest Moon is just the traditional name of the full moon nearest the autumnal equinox.  According to lore the name is a fitting one. Despite the diminishing daylight hours as the growing season drew to a close, farmers could harvest crops by the light of a full moon shining on from dusk to dawn. This September's Harvest Moon was also known to some as a supermoon, a term becoming a traditional name for a full moon near perigee.

Image credit: Petr Horálek
Sunrise Shadows in the Sky (2024-09-21)

The defining astronomical moment of this September's equinox is at 12:44 UTC on September 22, when the Sun crosses the celestial equator moving south in its yearly journey through planet Earth's sky. That marks the beginning of fall for our fair planet in the northern hemisphere and spring in the southern hemisphere, when day and night are nearly equal around the globe.  Of course, if you celebrate the astronomical change of seasons by watching a sunrise you can also look for crepuscular rays. Outlined by shadows cast by clouds, crepuscular rays can have a dramatic appearance in the twilight sky during any sunrise (or sunset). Due to perspective, the parallel cloud shadows will seem to point back to the rising Sun and a place due east on your horizon on the equinox date. But in this spectacular sunrise skyscape captured in early June, the parallel shadows and crepuscular rays appear to converge toward an eastern horizon's more northerly sunrise.  The well-composed photo places the rising Sun just behind the bell tower of a church in the town of Vic, province of Barcelona, Catalonia, Spain.

Image credit: Emili Vilamala
Chicagohenge: Equinox in an Aligned City (2024-09-22)

Chicago, in a way, is like a modern Stonehenge. The way is east to west, and the time is today.  Today, and every equinox, the Sun will set exactly to the west, everywhere on Earth. Therefore, today in Chicago, the Sun will set directly down the long equatorially-aligned grid of streets and buildings, an event dubbed #chicagohenge.  Featured here is a Chicago Henge picture taken during the  equinox in mid-September of 2017 looking along part of Upper Wacker Drive.  Many cities, though, have streets or other features that are well-aligned to Earth's spin axis. Therefore, quite possibly, your  favorite street may also run east - west. Tonight at sunset, with a quick glance, you can actually find out.

Image credit: Anthony Artese
Comet Tsuchinshan-ATLAS Approaches (2024-09-23)

What will happen as this already bright comet approaches?  Optimistic predictions have Comet C/2023 A3 (Tsuchinshan–ATLAS) briefly becoming easily visible to the unaided eye -- although the future brightness of comets are notoriously hard to predict, and this comet may even break up in warming sunlight. What is certain is that the comet is now unexpectedly bright and is on track to pass its closest to the Sun (0.39 AU) later this week and closest to the Earth (0.47 AU) early next month.  The featured image was taken in late May as Comet Tsuchinshan–ATLAS, discovered only last year, passed nearly in front of two distant galaxies.  The comet can now be found with binoculars in the early morning sky rising just before the Sun, while over the next few weeks it will brighten as it moves to the early evening sky.   Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)

Image credit: Brian Valente
& Greg Stein
NGC 6727: The Rampaging Baboon Nebula (2024-09-24)

This dusty region is forming stars. Part of a sprawling molecular cloud complex that resembles, to some, a rampaging baboon, the region is a relatively close by 500 light-years away toward the constellation Corona Australis. That's about one third the distance of the more famous stellar nursery known as the Orion Nebula.  Mixed with bright nebulosities, the brown dust clouds effectively block light from more distant background stars in the Milky Way and obscure from view embedded stars still in the process of formation.  The eyes of the dust creature in the featured image are actually blue reflection nebulas cataloged as NGC 6726, 6727, 6729, and IC 4812, while the red mouth glows with light emitted by hydrogen gas.  Just to the upper left of the baboon's head is NGC 6723, a whole globular cluster of stars nearly 30,000 light years in the distance.    Explore Your Universe: Random APOD Generator

Image credit: Alpha Zhang & 
Ting Yu
Comet A3 Through an Australian Sunrise (2024-09-25)

Comet Tsuchinshan-ATLAS is now visible in the early morning sky.  Diving into the inner Solar System at an odd angle, this large dirty iceberg will pass its closest to the Sun -- between the orbits of Mercury and Venus -- in just two days. Long camera exposures are now capturing C/2023 A3 (Tsuchinshan–ATLAS), sometimes abbreviated as just A3, and its dust tail before and during sunrise.  The featured image composite was taken four days ago and captured the comet as it rose above Lake George, NSW, Australia.  Vertical bands further left are images of the comet as the rising Sun made the predawn sky increasingly bright and colorful. Just how bright the comet will become over the next month is currently unknown as it involves how much gas and dust the comet's nucleus will expel. Optimistic skywatchers are hoping for a great show where Tsuchinshan–ATLAS creates dust and ion tails visible across Earth's sky and becomes known as the Great Comet of 2024.   Survey: Color Blindness and Astronomical Images  Growing Gallery: Comet Tsuchinsan-ATLAS in 2024

Image credit: Lucy Yunxi Hu
The Great Globular Cluster in Hercules (2024-09-26)

In 1716, English astronomer Edmond Halley noted, "This is but a little Patch, but it shows itself to the naked Eye, when the Sky is serene and the Moon absent." Of course, M13 is now less modestly recognized as the Great Globular Cluster in Hercules, one of the brightest globular star clusters in the northern sky. Sharp telescopic views like this one reveal the spectacular cluster's hundreds of thousands of stars. At a distance of 25,000 light-years, the cluster stars crowd into a region 150 light-years in diameter. Approaching the cluster core, upwards of 100 stars could be contained in a cube just 3 light-years on a side. For comparison, the closest star to the Sun is over 4 light-years away. The deep, wide-field image also reveals distant background galaxies including NGC 6207 at the upper left, and faint, foreground Milky Way dust clouds known to some as integrated flux nebulae.

Image credit: Jan Beckmann, Julian Zoller, Lukas Eisert, Wolfgang Hummel
Stellar Streams in the Local Universe (2024-09-27)

The twenty galaxies arrayed in these panels are part of an ambitious astronomical survey of tidal stellar streams. Each panel presents a composite view; a deep, inverted image taken from publicly available imaging surveys of a field that surrounds a nearby massive galaxy image. The inverted images reveal faint cosmic structures, star streams hundreds of thousands of light-years across, that result from the gravitational disruption and eventual merger of satellite galaxies in the local universe. Such surveys of mergers and gravitational tidal interactions between massive galaxies and their dwarf satellites are crucial guides for current models of galaxy formation and cosmology. Of course, the detection of stellar streams in the neighboring Andromeda Galaxy and our own Milky Way also offers spectacular evidence for ongoing satellite galaxy disruption within our more local galaxy group.
Rocket Eclipse at Sunset (2024-09-28)

Shockwaves ripple across the glare as a launch eclipses the setting Sun in this exciting close-up. Captured on September 17, the roaring Falcon 9 rocket carried European Galileo L13 navigation satellites to medium Earth orbit after a lift-off from Cape Canaveral on Florida's space coast.  The Falcon 9 booster returned safely to Earth about 8.5 minutes later, notching the 22nd launch and landing for the reusable workhorse launch vehicle. But where did it land? Just Read the Instructions.

Image credit: Ben Cooper
Seven Dusty Sisters (2024-09-29)

Is this really the famous Pleiades star cluster? Known for its iconic blue stars, the Pleiades is shown here in infrared light where the surrounding dust outshines the stars. Here, three infrared colors have been mapped into visual colors (R=24, G=12, B=4.6 microns). The base images were taken by NASA's orbiting Wide Field Infrared Survey Explorer (WISE) spacecraft. Cataloged as M45 and nicknamed the Seven Sisters, the Pleiades star cluster is by chance situated in a passing dust cloud. The light and winds from the massive Pleiades stars preferentially repel smaller dust particles, causing the dust to become stratified into filaments, as seen. The featured image spans about 20 light years at the distance of the Pleiades, which lies about 450 light years distant toward the constellation of the Bull (Taurus).
Comet Tsuchinshan-ATLAS over Mexico (2024-09-30)

The new comet has passed its closest to the Sun and is now moving closer to the Earth. C/2023 A3 (Tsuchinshan–ATLAS) is currently moving out from inside the orbit of Venus and on track to pass its nearest to the Earth in about two weeks.  Comet Tsuchinshan-ATLAS, pronounced "Choo-cheen-shahn At-less,", is near naked-eye visibility and easily picked up by long-exposure cameras.  The comet can also now be found by observers in Earth's northern hemisphere as well as the south.  The featured image was captured just a few days ago above Zacatecas, Mexico. Because clouds were obscuring much of the pre-dawn sky, the astrophotographer released a drone to take pictures from higher up, several of which were later merged to enhance the comet's visibility. Although the future brightness of comets is hard to predict, there is increasing hope that Comet Tsuchinshan-ATLAS will further brighten as it enters the early evening sky.   Growing Gallery: Comet Tsuchinsan-ATLAS in 2024

Image credit: Daniel Korona
Porphyrion: The Longest Known Black Hole Jets (2024-10-01)

How far can black hole jets extend? A new record was found just recently with the discovery of a 23-million light-year long jet pair from a black hole active billions of years ago.  Dubbed Porphyrion for a mythological Greek giant, the impressive jets were created by a type of black hole that does not usually create long jets -- one that is busy creating radiation from infalling gas. The featured animated video depicts what it might look like to circle around this powerful black hole system.  Porphyrion is shown as a fast stream of energetic particles, and the bright areas are where these particles are impacting surrounding gas. The discovery was made using data from the Keck and Mayall  (DESI) optical observatories as well as LOFAR and the Giant Metrewave Radio Telescope.  The existence of these jets demonstrates that black holes can affect not only their home galaxies but far out into the surrounding universe.   Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)
The Large Magellanic Cloud Galaxy (2024-10-02)

It is the largest satellite galaxy of our home Milky Way Galaxy. If you live in the south, the Large Magellanic Cloud (LMC) is quite noticeable, spanning about 10 degrees across the night sky, which is 20 times larger than the full moon towards the southern constellation of the dolphinfish (Dorado). Being only about 160,000 light years away, many details of the LMC's structure can be seen, such as its central bar and its single spiral arm. The LMC harbors numerous stellar nurseries where new stars are being born, which appear in pink in the featured image. It is home to the Tarantula Nebula, the currently most active star forming region in the entire Local Group, a small collection of nearby galaxies dominated by the massive Andromeda and Milky Way galaxies. Studies of the LMC and the Small Magellanic Cloud (SMC) by Henrietta Swan Leavitt led to the discovery of the period-luminosity relationship of Cepheid variable stars that are used to measure distances across the nearby universe.   Survey: Color Blindness and Astronomical Images

Image credit: Ireneusz Nowak;  
Text: Natalia Lewandowska 
(SUNY Oswego)
Eclipse at Sunrise (2024-10-03)

The second solar eclipse of 2024 began in the Pacific. On October 2nd the Moon's shadow swept from west to east, with an annular eclipse visible along a narrow antumbral shadow path tracking mostly over ocean, crossing land near the southern tip of South America, and ending in the southern Atlantic. The dramatic total annular eclipse phase is known to some as a ring of fire. Still, a partial eclipse of the Sun was experienced over a wide region. Captured at one of its earliest moments, October's eclipsed Sun is seen just above the clouds near sunrise in this snapshot. The partially eclipsed solar disk is close to the maximum eclipse as seen from Mauna Kea Observatory Visitor Center, Island of Hawaii, planet Earth.   Growing Gallery: Annular Solar Eclipse 2024 October

Image credit: Wang Letian
Comet at Moonrise (2024-10-04)

Comet C/2023 A3 (Tsuchinshan–ATLAS) is growing brighter in planet Earth's sky. Fondly known as comet A3, this new visitor to the inner Solar System is traveling from the distant Oort cloud. The comet reached perihelion, its closest approach to the Sun, on September 27 and will reach perigee, its closest to our fair planet, on October 12, by then becoming an evening sky apparition. But comet A3 was an early morning riser on September 30 when this image was made. Its bright coma and already long tail share a pre-dawn skyscape from Praia Grande, Santa Catarina in southern Brazil with the waning crescent Moon just peeking above the eastern horizon. While the behaviour of comets is notoriously unpredictable, Tsuchinshan–ATLAS could become a comet visually rivaling C/2020 F3 (NEOWISE). Comet NEOWISE wowed skygazers in the summer of 2020.   Growing Gallery: Comet Tsuchinsan-ATLAS in 2024

Image credit: Gabriel Zaparolli
M27: Not a Comet (2024-10-05)

While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things encountered during his telescopic expeditions that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it's not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula. This impressive color image highlights details within the well-studied central region and fainter, seldom imaged features in the nebula's outer halo.

Image credit: Francesco Sferlazza, Franco Sgueglia
The Magnificent Tail of Comet McNaught (2024-10-06)

Comet McNaught, the Great Comet of 2007, grew a spectacularly long and filamentary tail.  The magnificent tail spread across the sky and was visible for several days to Southern Hemisphere observers just after sunset.  The amazing ion tail showed its greatest extent on long-duration, wide-angle camera exposures.  During some times, just the tail itself was visible just above the horizon for many northern observers as well. Comet C/2006 P1 (McNaught), estimated to have attained a peak brightness of  magnitude -5 (minus five), was caught by the comet's discoverer in the featured image just after sunset in January 2007 from Siding Spring Observatory in Australia. Comet McNaught, the brightest comet in decades, then  faded as it moved further into southern skies and away from the Sun and Earth. Over the next month, Comet Tsuchinshan–ATLAS, a candidate for the Great Comet of 2024, should display its most spectacular tails  visible from the Earth.

Image credit: Robert H. McNaught
The Long Tails Comet Tsuchinshan-ATLAS (2024-10-07)

A bright comet is moving into the evening skies. C/2023 A3 (Tsuchinshan–ATLAS) has brightened and even though it is now easily visible to the unaided eye, it is so near to the Sun that it is still difficult to see. Pictured, Comet Tsuchinshan–ATLAS was captured just before sunrise from an Andes Mountain in Peru. Braving cold weather, this unusually high perch gave the astrophotographer such a low eastern horizon that the comet was obvious in the pre-dawn sky.  Visible in the featured image is not only an impressively long dust tail extending over many degrees, but an impressively long and blue ion tail, too.  This month, as the comet moves out from the Sun and passes the Earth, evening observers should be able to see the huge dirty ice ball toward the west just after sunset.   Growing Gallery: Comet Tsuchinsan-ATLAS in 2024

Image credit: Jose Santivañez Mueras
Annular Eclipse over Patagonia (2024-10-08)

Can you find the Sun? OK, but can you explain why there’s a big dark spot in the center? The spot is the Moon, and the impressive alignment shown, where the Moon lines up inside the Sun, is called an annular solar eclipse. Such an eclipse occurred just last week and was visible from a thin swath mostly in Earth's southern hemisphere. The featured image was captured from Patagonia, Chile. When the Moon is significantly closer to the Earth and it aligns with the Sun, a total solar eclipse is then visible from parts of the Earth. Annular eclipses are slightly more common than total eclipses, but as the Moon moves slowly away from the Earth, before a billion more years, the Moon's orbit will no longer bring it close enough for a total solar eclipse to be seen from anywhere on Earth.   Gallery: Annular Eclipse of October 2024

Image credit: Alexis
Trigo
M106: A Spiral Galaxy with a Strange Center (2024-10-09)

What's happening at the center of spiral galaxy M106? A swirling disk of stars and gas, M106's appearance is dominated by blue spiral arms and red  dust lanes near the nucleus, as shown in the featured image taken from the Kuwaiti desert.  The core of M106 glows brightly in radio waves and X-rays where twin jets have been found running the length of the galaxy.  An unusual central glow makes M106 one of the closest examples of the Seyfert class of galaxies, where vast amounts of glowing gas are thought to be falling into a central massive black hole.  M106, also designated NGC 4258, is a relatively close 23.5 million light years away, spans 60 thousand light years across, and can be seen with a small telescope towards the constellation of the Hunting Dogs (Canes Venatici).

Image credit: Ali Al Obaidly
Five Bright Comets from SOHO (2024-10-10)

Five bright comets are compared in these panels, recorded by a coronograph on board the long-lived, sun-staring SOHO spacecraft. Arranged chronologically all are recognizable by their tails streaming away from the Sun at the center of each field of view, where a direct view of the overwhelmingly bright Sun is blocked by the coronagraph's occulting disk. Each comet was memorable for earthbound skygazers, starting at top left with Comet McNaught, the 21st century's brightest comet (so far). C/2023 A3 Tsuchinshan-ATLAS, following its perihelion with the active Sun at bottom center, has most recently grabbed the attention of comet watchers around the globe. By the end of October 2024, the blank 6th panel may be filled with bright sungrazer comet C/2024 S1 (ATLAS). ... or not.