juliensimon/nasa-apod huggingface dataset:
NGC 1566: A Spiral Galaxy from Webb and Hubble (2024-02-06)

What's different about this galaxy? Very little, which makes the Spanish Dancer galaxy, NGC 1566, one of the most typical and photogenic spirals on the sky. There is something different about this galaxy image, though, because it is a diagonal combination of two images: one by the Hubble Space Telescope on the upper left, and the other by the James Webb Space Telescope on the lower right.  The Hubble image was taken in ultraviolet light and highlights the locations of bright blue stars and dark dust along the galaxy's impressive spiral arms. In contrast, the Webb image was taken in infrared light and highlights where the same dust emits more light than it absorbed. In the rollover image, the other two sides of these images are revealed. Blinking between the two images shows which stars are particularly hot because they glow brighter in ultraviolet light, and the difference between seemingly empty space and infrared-glowing dust.   Image Crunching Opportunity:  Take NASA's Astrophoto Challenge

Image credit: NASA, 
ESA, 
CSA, 
STScI, 
J. Lee (STScI), 
T. Williams (Oxford), 
R. Chandar (UToledo), 
D. Calzetti (UMass), 
PHANGS Team
The Heart Shaped Antennae Galaxies (2024-02-07)

Are these two galaxies really attracted to each other? Yes, gravitationally, and the result appears as an enormous iconic heart -- at least for now. Pictured is the pair of galaxies cataloged as NGC 4038 and NGC 4039,known as the Antennae Galaxies.  Because they are only 60 million light years away, close by intergalactic standards, the pair is one of the best studied interacting galaxies on the night sky. Their strong attraction began about a billion years ago when they passed unusually close to each other.  As the two galaxies interact, their stars rarely collide, but new stars are formed when their interstellar gases crash together.  Some new stars have already formed, for example, in the long antennae seen extending out from the sides of the dancing duo. By the time the galaxy merger is complete, likely over a billion years from now, billions of new stars may have formed.   Open Science: Browse 3,300+ codes in the Astrophysics Source Code Library

Image credit: Kent E. Biggs
Globular Star Cluster 47 Tuc (2024-02-08)

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: Marco Lorenzi
When Roses Aren't Red (2024-02-09)

Not all roses are red of course, but they can still be very pretty. Likewise, the beautiful Rosette Nebula and other star forming regions are often shown in astronomical images with a predominately red hue, in part because the dominant emission in the nebula is from hydrogen atoms. Hydrogen's strongest optical emission line, known as H-alpha, is in the red region of the spectrum. But the beauty of an emission nebula need not be appreciated in red light alone. Other atoms in the nebula are also excited by energetic starlight and produce narrow emission lines as well. In this close-up view of the Rosette Nebula, narrowband images are mapped into broadband colors to show emission from Sulfur atoms in red, Hydrogen in green, and Oxygen in blue. In fact, the scheme of mapping these narrow atomic emission lines (SHO) into the broader colors (RGB) is adopted in many Hubble images of emission nebulae. This image spans about 50 light-years across the center of the Rosette Nebula. The nebula lies some 3,000 light-years away in the constellation Monoceros.

Image credit: Tommy Lease
The Shadow of Ingenuity's Damaged Rotor Blade (2024-02-10)

On January 18, 2024, during its 72nd flight in the thin Martian atmosphere, autonomous Mars Helicopter Ingenuity rose to an altitude of 12 meters (40 feet) and hovered for 4.5 seconds above the Red Planet.  Ingenuity's 72nd landing was a rough one though. During descent it lost contact with the Perseverance rover about 1 meter above the Martian surface. Ingenuity was able to transmit this image after contact was re-established, showing the shadow of one of its rotor blades likely damaged during landing. And so, after wildly exceeding expectations during over 1,000 days of exploring Mars, the history-making Ingenuity has ended its flight operations. Nicknamed Ginny, Mars Helicopter Ingenuity became the first aircraft to achieve powered, controlled flight on another planet on April 19, 2021. Before launch, a small piece of material from the lower-left wing of the Wright Brothers Flyer 1, the first aircraft to achieve powered, controlled flight on planet Earth, was fixed to the underside of Ingenuity's solar panel.
Rocket Plume Shadow Points to the Moon (2024-02-11)

Why would the shadow of a rocket's launch plume point toward the Moon?  In early 2001 during a launch of the space shuttle Atlantis, the Sun, Earth, Moon, and rocket were all properly aligned for this photogenic coincidence.  First, for the space shuttle's plume to cast a long shadow, the time of day must be either near sunrise or sunset.  Only then will the shadow be its longest and extend all the way to the horizon.  Finally, during a Full Moon, the Sun and Moon are on opposite sides of the sky.  Just after sunset, for example, the Sun is slightly below the horizon, and, in the other direction, the Moon is slightly above the horizon.  Therefore, as Atlantis blasted off, just after sunset, its shadow projected away from the Sun toward the opposite horizon, where the Full Moon happened to be.    Almost Hyperspace: Random APOD Generator
HFG1 & Abell 6: Planetary Nebulae (2024-02-12)

Planetary nebulae like Heckathorn-Fesen-Gull 1 (HFG1) and Abell 6 in the constellation Cassiopeia are remnants from the last phase of a medium sized star like our Sun.  In spite of their shapes, planetary nebulae have nothing in common with actual planets.  Located in the bottom left part of the featured photo, HFG1 was created by the binary star system V664 Cas, which consists of a white dwarf star and a red giant star. Both stars orbit their center of mass over about half an Earth day.  Traveling with the entire nebula at a speed about 300 times faster than the fastest train on Earth, V664 Cas generates a bluish arc shaped shock wave. The wave interacts most strongly with the surrounding interstellar medium in the areas where the arc is brightest. After roughly 10,000 years, planetary nebulae become invisible due to a lack of ultraviolet light being emitted by the stars that create them.  Displaying beautiful shapes and structures, planetary nebulae are highly desired objects for astrophotographers.

Image credit: Julien Cadena & 
Mickael Coulon; 
Text: Natalia Lewandowska 
(SUNY Oswego)
A January Wolf Moon (2024-02-13)

Did you see the full moon last month? During every month, on average, a full moon occurs in the skies over planet Earth. This is because the Moon takes a month to complete another orbit around our home planet, goes through all of its phases, and once again has its entire Earth-facing half lit by reflected sunlight.  Many indigenous cultures give each full moon a name, and this past full moon's names include the Ice Moon, the Stay at Home Moon, and the Quiet Moon. Occurring in January on the modern western calendar, several cultures have also named the most recent full moon the Wolf Moon, in honor of the famous howling animal. Featured here above the Italian Alps mountains, this past Wolf Moon was captured in combined long and short exposure images.  The image is striking because, to some, the surrounding clouds appear as a wolf's mouth ready to swallow the Wolf Moon, while others see the Moon as a wolf's eye.

Image credit: Antoni Zegarski
Rosette Deep Field (2024-02-14)

Can you find the Rosette Nebula? The large, red, and flowery-looking nebula on the upper left may seem the obvious choice, but that is actually just diffuse hydrogen emission surrounding the Cone and Fox Fur Nebulas. The famous Rosette Nebula is really located on the lower right and connected to the other nebulas by irregular filaments.  Because the featured image of Rosetta's field is so wide and deep, it seems to contain other flowers.  Designated NGC 2237, the center of the Rosette nebula is populated by the bright blue stars of open cluster NGC 2244, whose winds and energetic light are evacuating the nebula's center.  The Rosette Nebula is about 5,000 light years distant and, just by itself, spans about three times the diameter of a full moon. This flowery field can be found toward the constellation of the Unicorn  (Monoceros).

Image credit: Olivier Bernard & 
Philippe Bernhard
NGC 253: Dusty Island Universe (2024-02-15)

Shiny NGC 253 is one of the brightest spiral galaxies visible, and also one of the dustiest.  Some call it the Silver Coin Galaxy for its appearance in small telescopes, or just the Sculptor Galaxy for its location within the boundaries of the southern constellation Sculptor.  Discovered in 1783 by mathematician and astronomer Caroline Herschel, the dusty island universe lies a mere 10 million light-years away. About 70 thousand light-years across, NGC 253 is the largest member of the Sculptor Group of Galaxies, the nearest to our own Local Group of Galaxies.  In addition to its spiral dust lanes, tendrils of dust seem to be rising from its galactic disk laced with young star clusters and star forming regions in this colorful galaxy portrait. The high dust content accompanies frantic star formation, earning NGC 253 the designation of a starburst galaxy. NGC 253 is also known to be a strong source of high-energy x-rays and gamma rays, likely due to massive black holes near the galaxy's center.

Image credit: Steve Crouch
Structure in the Tail of Comet 12P/Pons-Brooks (2024-02-16)

Heading for its next perihelion passage on April 21, Comet 12P/Pons-Brooks is growing brighter. The greenish coma of this periodic Halley-type comet has become relatively easy to observe in small telescopes. But the bluish ion tail now streaming from the active comet's coma and buffeted by the solar wind, is faint and difficult to follow. Still, in this image stacked exposures made on the night of February 11 reveal the fainter tail's detailed structures. The frame spans over two degrees across a background of faint stars and background galaxies toward the northern constellation Lacerta. Of course Comet 12P's April 21 perihelion passage will be only two weeks after the April 8 total solar eclipse, putting the comet in planet Earth's sky along with a totally eclipsed Sun.

Image credit: Dan Bartlett
Meteor over the Bay of Naples (2024-02-17)

A cosmic dust grain plowing through the upper atmosphere much faster than a falling leaf created this brilliant meteor streak. In a serendipitous moment, the sublime night sky view was captured from the resort island of Capri, in the Bay of Naples, on the evening of February 8. Looking across the bay, the camera faces northeast toward the lights of Naples and surrounding cities. Pointing toward the horizon, the meteor streak by chance ends above the silhouette of Mount Vesuvius. One of planet Earth's most famous volcanos, an eruption of Mount Vesuvius destroyed the city of Pompeii in 79 AD.

Image credit: Wang Letian
Hoag's Object: A Nearly Perfect Ring Galaxy (2024-02-18)

Is this one galaxy or two?  This question came to light in 1950 when astronomer Arthur Hoag chanced upon this unusual extragalactic object.  On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older.  Between the two is a gap that appears almost completely dark.  How Hoag's Object formed, including its nearly perfectly round ring of stars and gas, remains unknown.  Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. The featured photo was taken by the Hubble Space Telescope and reprocessed using an artificially intelligent de-noising algorithm.  Observations in radio waves indicate that Hoag's Object has not accreted a smaller galaxy in the past billion years.  Hoag's Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens).  Many galaxies far in the distance are visible toward the right, while coincidentally, visible in the gap at about seven o'clock, is another but more distant ring galaxy.
Looking Sideways from the Parker Solar Probe (2024-02-19)

What's happening near the Sun?  To help find out, NASA launched the robotic Parker Solar Probe (PSP) to investigate regions closer to the Sun than ever before. The PSP's looping orbit brings it nearer to the Sun each time around -- every few months. The featured time-lapse video shows the view looking sideways from behind PSP's Sun shield during its 16th approach to the Sun last year -- from well within the orbit of Mercury.  The PSP's Wide Field Imager for Solar Probe (WISPR) cameras took the images over eleven days, but they are digitally compressed here into about one minute video.  The waving of the solar corona is visible, as is a coronal mass ejection, with stars, planets, and even the central band of our Milky Way Galaxy streaming by in the background as the PSP orbits the Sun. PSP has found the solar neighborhood to be surprisingly complex and to include switchbacks -- times when the Sun's magnetic field briefly reverses itself.
AM1054: Stars Form as Galaxies Collide (2024-02-20)

When galaxies collide, how many stars are born?  For AM1054-325, featured here in a recently released image by the Hubble Space Telescope, the answer is millions. Instead of stars being destroyed as galaxy AM1054-325 and a nearby galaxy circle each other, their gravity and motion has ignited stellar creation.  Star formation occurs rapidly in the gaseous debris stretching from AM1054-325’s yellowish body due to the other galaxy’s gravitational pull.  Hydrogen gas surrounding newborn stars glows pink.  Bright infant stars shine blue and cluster together in compact nurseries of thousands to millions of stars. AM1054-325 possesses over 100 of these intense-blue, dot-like star clusters, some appearing like a string of pearls.  Analyzing ultraviolet light helped determine that most of these stars are less than 10 million years old: stellar babies.  Many of these nurseries may grow up to be globular star clusters, while the bundle of young stars at the bottom tip may even detach and form a small galaxy.
Seagull Nebula over Pinnacles' Peak (2024-02-21)

The bird is bigger than the peak.  Nicknamed for its avian shape, the Seagull Nebula is an emission nebula on the night sky that is vast, spanning an angle over five times the diameter of the full moon and over 200 light years.  The head of the nebula is catalogued as IC 2177, and the star cluster under its right wing is catalogued as NGC 2343. Consisting of mostly red-glowing hydrogen gas, the Seagull Nebula incorporates some dust lanes and is forming stars.  The peak over which this Seagull seems to soar occurs at Pinnacles National Park in California, USA.  The featured image is a composite of long exposure images of the background sky and short exposure images of the foreground, all taken consecutively with the same camera and from the same location.    Explore Your Universe: Random APOD Generator

Image credit: Dheera Venkatraman
A View Toward M106 (2024-02-22)

Big, bright, beautiful spiral, Messier 106 dominates this cosmic vista. The nearly two degree wide telescopic field of view looks toward the well-trained constellation Canes Venatici, near the handle of the Big Dipper. Also known as NGC 4258, M106 is about 80,000 light-years across and 23.5 million light-years away, the largest member of the Canes II galaxy group. For a far far away galaxy, the distance to M106 is well-known in part because it can be directly measured by tracking this galaxy's remarkable maser, or microwave laser emission. Very rare but naturally occurring, the maser emission is produced by water molecules in molecular clouds orbiting its active galactic nucleus. Another prominent spiral galaxy on the scene, viewed nearly edge-on, is NGC 4217 below and right of M106. The distance to NGC 4217 is much less well-known, estimated to be about 60 million light-years, but the bright spiky stars are in the foreground, well inside our own Milky Way galaxy.

Image credit: Kyunghoon Lim
The Pencil Nebula Supernova Shock Wave (2024-02-23)

This supernova shock wave plows through interstellar space at over 500,000 kilometers per hour. Centered and moving upward in the sharply detailed color composite its thin, bright, braided filaments are actually long ripples in a cosmic sheet of glowing gas seen almost edge-on. Discovered in the 1840s by Sir John Herschel, the narrow-looking nebula is sometimes known as Herschel's Ray. Cataloged as NGC 2736, its pointed appearance suggests its modern popular name, the Pencil Nebula. The Pencil Nebula is about 800 light-years away. Nearly 5 light-years long it represents only a small part of the Vela supernova remnant though. The enormous Vela remnant itself is around 100 light-years in diameter, the expanding debris cloud of a star that was seen to explode about 11,000 years ago. Initially, the section of the shock wave seen as the Pencil nebula was moving at millions of kilometers per hour but has slowed considerably, sweeping up surrounding interstellar material.

Image credit: Helge Buesing
Odysseus to the Moon (2024-02-24)

Intuitive Machines' robotic lander Odysseus has accomplished the first U.S. landing on the Moon since the Apollo 17 mission in 1972. Launched on a SpaceX rocket on February 15, the phone booth sized lander reached lunar orbit on the 21st and touched down on the lunar surface at 6:23 pm ET on February 22nd. Its landing region is about 300 kilometers north of the Moon's south pole, near a crater designated Malapert A. Resting on its side, the lander is presently collecting solar power and transmitting data back to the Intuitive Machines' mission control center in Houston. The mission marks the first commercial uncrewed landing on the Moon. Prior to landing, Odysseus’ camera captured this extreme wide angle image (landing legs visible at right) as it flew over Schomberger crater some 200 kilometers from its landing site. Odysseus was still about 10 kilometers above the lunar surface.
A Phoenix Aurora over Iceland (2024-02-25)

All of the other aurora watchers had gone home. By 3:30 am in Iceland, on a quiet September night, much of that night's auroras had died down. Suddenly, unexpectedly, a new burst of particles streamed down from space, lighting up the Earth's atmosphere once again. This time, surprisingly, pareidoliacally, the night lit up with an  amazing shape reminiscent of a giant phoenix. With camera equipment at the ready, two quick sky images were taken, followed immediately by a third of the land.  The mountain in the background is Helgafell, while the small foreground river is called Kaldá, both located about 30 kilometers north of Iceland's capital Reykjavík. Seasoned skywatchers will note that just above the mountain, toward the left, is the constellation of Orion, while the Pleiades star cluster is also visible just above the frame center.  The 2016 aurora, which lasted only a minute and was soon gone forever --  would possibly be dismissed as a fanciful fable -- were it not captured in the featured, digitally-composed, image mosaic.   Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)

Image credit: Hallgrimur P. Helgason;
 Rollover Annotation: 
Judy Schmidt
Martian Moon Eclipses Martian Moon (2024-02-26)

What if there were two moons in the sky -- and they eclipsed each other? This happens on Mars. The featured video shows a version of this unusual eclipse from space. Pictured are the two moons of Mars: the larger Phobos, which orbits closer to the red planet, and the smaller Deimos, which orbits further out. The sequence was captured last year by the ESA’s Mars Express, a robotic spacecraft that itself orbits Mars. A similar eclipse is visible from the Martian surface, although very rarely.  From the surface, though, the closer moon Phobos would appear to pass in front of farther moon Deimos. Most oddly, Phobos orbits Mars so close that it appears to move backwards when compared to Earth's Moon from Earth, rising in west and setting in the east. Phobos, the closer moon, orbits so close and so fast that it passes nearly overhead about three times a day.
Supernova Remnant Simeis 147 (2024-02-27)

It's easy to get lost following the intricate, looping, and twisting filaments of supernova remnant Simeis 147.  Also cataloged as Sharpless 2-240, the filamentary nebula goes by the popular nickname the Spaghetti Nebula.  Seen toward the boundary of the constellations of the Bull (Taurus) and the Charioteer (Auriga), the impressive gas structure covers nearly 3 degrees on the sky, equivalent to 6 full moons. That's about 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years.  This composite image includes data taken through narrow-band filters isolating emission from hydrogen (red) and oxygen (blue) glowing gas. The supernova remnant has an estimated age of about 40,000 years, meaning light from this massive stellar explosion first reached the Earth when woolly mammoths roamed free.  Besides the expanding remnant, this cosmic catastrophe left behind a pulsar, a spinning neutron star that is the remnant of the original star's core.

Image credit: Stéphane Vetter
(Nuits sacrées)
Shades of Night (2024-02-28)

How does the sky turn dark at night? In stages, and with different characteristic colors rising from the horizon. The featured image shows, left to right, increasingly late twilight times after sunset in 20 different vertical bands. The picture was taken last month in Syracuse, Sicily, Italy, in the direction opposite the Sun. On the far left is the pre-sunset upper sky.  Toward the right, prominent bands include the Belt of Venus, the Blue Band, the Horizon Band, and the Red Band. As the dark shadow of the Earth rises, the colors in these bands are caused by direct sunlight reflecting from air and aerosols in the Earth's atmosphere, multiple reflections sometimes involving a reddened sunset, and refraction. In practice, these bands can be diffuse and hard to discern, and their colors can depend on colors near the setting Sun. Finally, the Sun completely sets and the sky becomes dark. Don't despair -- the whole thing will happen in reverse when the Sun rises again in the morning.

Image credit: Dario Giannobile