omnianasa/nasa-apod-metadata huggingface dataset:
Lunar Craters Langrenus and Petavius (2019-11-11)
The history of the Moon is partly written in its craters.  Pictured here is a lunar panorama taken from Earth featuring the large craters Langrenus, toward the left, and Petavius, toward the right. The craters formed in separate impacts. Langrenus spans about 130 km, has a terraced rim, and sports a central peak rising about 3 km.  Petavius is slightly larger with a 180 km diameter and has a distinctive fracture that runs out from its center. Although it is known that Petravius crater is about 3.9 billion years old, the origin of its large fracture is unknown.  The craters are best visible a few days after a new Moon, when shadows most greatly accentuate vertical walls and hills.  The featured image is a composite of the best of thousands of high-resolution, infrared, video images taken through a small telescope.  Although mountains on Earth will likely erode into soil over a billion years, lunar craters Langrenus and Petavius will likely survive many billions more years, possibly until the Sun expands and engulfs both the Earth and Moon.  Watch: the November 11 Transit of Mercury from Earth or from Space.
NGC 3717: A Nearly Sideways Spiral Galaxy (2019-11-12)
Some spiral galaxies are seen nearly sideways. Most bright stars in spiral galaxies swirl around the center in a disk, and seen from the side, this disk can appear quite thin.  Some spiral galaxies appear even thinner than NGC 3717, which is actually seen tilted just a bit.  Spiral galaxies form disks because the original gas collided with itself and cooled as it fell inward.  Planets may orbit in disks for similar reasons.  The featured image by the Hubble Space Telescope shows a light-colored central bulge composed of older stars beyond filaments of orbiting dark brown dust.  NGC 3717 spans about 100,000 light years and lies about 60 million light years away toward the constellation of the Water Snake (Hydra).   Mercury Crosses the Sun: Some notable images of 2019 transit submitted to APOD
Mercury in Silhouette (2019-11-13)
The small, dark, round spot in this solar close up is planet Mercury. In the high resolution telescopic image, a colorized stack of 61 sharp video frames, a turbulent array of photospheric convection cells tile the bright solar surface.  Mercury's more regular silhouette still stands out though. Of course, only inner planets Mercury and Venus can transit the Sun to appear in silhouette when viewed from planet Earth. For this November 11, 2019 transit of Mercury, the innermost planet's silhouette was a mere 1/200th the solar diameter. So even under clear daytime skies it was difficult to see without the aid of a safe solar telescope. Following its transit in 2016, this was Mercury's 4th of 14 transits across the solar disk in the 21st century. The next transit of Mercury will be on November 13, 2032.
Mercury and the Quiet Sun (2019-11-14)
On November 11, 2019 the Sun was mostly quiet, experiencing a minimum in its 11 year cycle of activity. In fact, the only spot visible was actually planet Mercury, making a leisurely 5 1/2 hour transit in front of the calm solar disk. About 1/200th the apparent diameter of the Sun, the silhouette of the solar system's inner most planet is near center in this sharp, full Sun snapshot. Taken with a hydrogen alpha filter and safe solar telescope, the image also captures prominences around the solar limb, the glowing plasma trapped in arcing magnetic fields. Of course, only inner planets Mercury and Venus can transit the Sun to appear in silhouette when viewed from planet Earth. Following its transit in 2016, this was Mercury's 4th of 14 transits across the solar disk in the 21st century. The next transit of Mercury will be on November 13, 2032.
M16 and the Eagle Nebula (2019-11-15)
A star cluster around 2 million years young surrounded by natal clouds of dust and glowing gas, M16 is also known as The Eagle Nebula. This beautifully detailed portrait of the region was made with groundbased narrow and broadband image data. It includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the ridge of bright emission at lower left is another dusty starforming column known as the Fairy of Eagle Nebula. M16 lies about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).
The Star Streams of NGC 5907 (2019-11-16)
Grand tidal streams of stars seem to surround galaxy NGC 5907. The arcing structures form tenuous loops extending more than 150,000 light-years from the narrow, edge-on spiral, also known as the Splinter or Knife Edge Galaxy. Recorded only in very deep exposures, the streams likely represent the ghostly trail of a dwarf galaxy - debris left along the orbit of a smaller satellite galaxy that was gradually torn apart and merged with NGC 5907 over four billion years ago. Ultimately this remarkable discovery image, from a small robotic observatory in New Mexico, supports the cosmological scenario in which large spiral galaxies, including our own Milky Way, were formed by the accretion of smaller ones. NGC 5907 lies about 40 million light-years distant in the northern constellation Draco.
Young Stars in the Rho Ophiuchi Cloud (2019-11-17)
How do stars form? To help find out, astronomers created this tantalizing false-color composition of dust clouds and embedded newborn stars in infrared wavelengths with WISE, the Wide-field Infrared Survey Explorer. The cosmic canvas features one of the closest star forming regions, part of the Rho Ophiuchi cloud complex some 400 light-years distant near the southern edge of the pronounceable constellation Ophiuchus. After forming along a large cloud of cold molecular hydrogen gas, young stars heat the surrounding dust to produce the infrared glow. Stars in the process of formation, called young stellar objects or YSOs, are embedded in the compact pinkish nebulae seen here, but are otherwise hidden from the prying eyes of optical telescopes. An exploration of the region in penetrating infrared light has detected emerging and newly formed stars whose average age is estimated to be a mere 300,000 years. That's extremely young compared to the Sun's age of 5 billion years. The prominent reddish nebula at the lower right surrounding the star Sigma Scorpii is a reflection nebula produced by dust scattering starlight. This view from WISE, released in 2012, spans almost 2 degrees and covers about 14 light-years at the estimated distance of the Rho Ophiuchi cloud.
Milky Way over Uruguayan Lighthouse (2019-11-19)
Can a lighthouse illuminate a galaxy? No, but in the featured image, gaps in light emanating from the Jose Ignacio Lighthouse in Uruguay appear to match up nicely, although only momentarily and coincidently, with dark dust lanes of our Milky Way Galaxy. The bright dot on the right is the planet Jupiter.  The central band of the Milky Way Galaxy is actually the central spiral disk seen from within the disk. The Milky Way band is not easily visible through city lights but can be quite spectacular to see in dark skies.  The featured picture is actually the addition of ten consecutive images taken by the same camera from the same location.  The images were well planned to exclude direct light from the famous lighthouse.
Arp 273: Battling Galaxies from Hubble (2019-11-20)
What's happening to these spiral galaxies? Although details remain uncertain, there sure seems to be a titanic battle going on.  The upper galaxy is labelled UGC 1810 by itself, but together with its collisional partners is known as Arp 273. The overall shape of the UGC 1810 -- in particular its blue outer ring -- is likely a result of wild and violent gravitational interactions. The blue color of the outer ring at the top is caused by massive stars that are blue hot and have formed only in the past few million years.  The inner part of the upper galaxy -- itself an older spiral galaxy -- appears redder and threaded with cool filamentary dust.  A few bright stars appear well in the foreground, unrelated to colliding galaxies, while several far-distant galaxies are visible in the background.  Arp 273 lies about 300 million light years away toward the constellation of Andromeda.  Quite likely, UGC 1810 will devour its galactic sidekicks over the next billion years and settle into a classic spiral form.
Simeis 147: Supernova Remnant (2019-11-21)
It's easy to get lost following the intricate looping filaments in this detailed image of supernova remnant Simeis 147. Also cataloged as Sharpless 2-240 it goes by the popular nickname, the Spaghetti Nebula. Seen toward the boundary of the constellations Taurus and Auriga, it covers nearly 3 degrees or 6 full moons on the sky. That's about 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. This composite includes image data taken through narrow-band filters where reddish emission from ionized hydrogen atoms and doubly ionized oxygen atoms in faint blue-green hues trace the shocked, glowing gas. The supernova remnant has an estimated age of about 40,000 years, meaning light from the massive stellar explosion first reached Earth 40,000 years ago. But the expanding remnant is not the only aftermath. The cosmic catastrophe also left behind a spinning neutron star or pulsar, all that remains of the original star's core.
Orion Rising (2019-11-22)
Looking toward the east in the early hours of a September morning this single exposure made with tripod and camera captured a simple visual experience. Rising above the tree-lined slope are familiar stars in planet Earth's northern night and the constellation Orion the Hunter.  Brighter stars marking the celestial Hunter's shoulder (Betelgeuse), foot (Rigel), belt, and sword are clearly reflected in the calm waters from northern Latvia's Vitrupe river. Of course, winter is coming to planet Earth's northern hemisphere.   By then Orion and this beautiful starry vista will be seen rising in early evening skies.
Apollo 12 and Surveyor 3 Stereo View (2019-11-23)
Put on your red/blue glasses and gaze across the western Ocean of Storms on the surface of the Moon. The 3D view features Apollo 12 astronaut Pete Conrad visiting the Surveyor 3 spacecraft 50 years ago in November of 1969. Surveyor 3 had landed at the site on the inside slope of a small crater about 2 1/2 years earlier in April of 1967. Visible on the horizon beyond the far crater wall, Apollo 12's Lunar Module Intrepid touched down less than 200 meters (650 feet) away, easy moonwalking distance from the robotic Surveyor spacecraft. The stereo image was carefully created from two separate pictures (AS12-48-7133, AS12-48-7134) taken on the lunar surface. They depict the scene from only slightly different viewpoints, approximating the separation between human eyes.
Apollo 12: Self-Portrait (2019-11-24)
Is this image art?  50 years ago, Apollo 12 astronaut-photographer Charles "Pete" Conrad recorded this masterpiece while documenting colleague Alan Bean's lunar soil collection activities on  Oceanus Procellarum.  The featured image is dramatic and stark.  The harsh environment of the Moon's Ocean of Storms is echoed in Bean's helmet, a perfectly composed reflection of Conrad and the lunar horizon.  Works of photojournalists originally intent on recording the human condition on planet Earth, such as Lewis W. Hine's images from New York City in the early 20th century, or Margaret Bourke-White's magazine photography are widely regarded as art.  Similarly many documentary astronomy and space images might also be appreciated for their artistic and esthetic appeal.
NGC 6995: The Bat Nebula (2019-11-25)
Do you see the bat?  It haunts this cosmic close-up of the eastern Veil Nebula.  The Veil Nebula itself is a large supernova remnant, the expanding debris cloud from the death explosion of a massive star. While the Veil is roughly circular in shape and covers nearly 3 degrees on the sky toward the constellation of the Swan (Cygnus), the Bat Nebula, NGC 6995, spans only 1/2 degree, about the apparent size of the Moon. That translates to 12 light-years at the Veil's estimated distance, a reassuring 1,400 light-years from planet Earth. In the composite of image data recorded through broad and narrow band filters, emission from hydrogen atoms in the remnant is shown in red with strong emission from oxygen and nitrogen atoms shown in hues of blue. Of course, in the western part of the Veil lies another seasonal apparition: the Witch's Broom Nebula.
Venus and Jupiter on the Horizon (2019-11-26)
What are those two bright objects on the horizon? Venus and Jupiter. The two brightest planets in the night sky passed very close together -- angularly -- just two days ago.  In real space, they were just about as far apart as usual, since Jupiter (on the right) orbits the Sun around seven times farther out than Venus.  The planetary duo were captured together two days ago in a picturesque sunset sky from Llers, Catalonia, Spain between a tree and the astrophotographer's daughter.  These two planets will continue to stand out in the evening sky, toward the west, for the next few days, with a sliver of a crescent Moon and a fainter Saturn also visible nearby.  As November ends, Jupiter will sink lower into the sunset horizon with each subsequent night, while Venus will rise higher.  The next Jupiter-Venus conjunction will occur in early 2021.
Hoag's Object: A Nearly Perfect Ring Galaxy (2019-11-27)
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 recently 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.
Moon and Planets at Twilight (2019-11-28)
This week's ongoing conjunction of Venus and Jupiter may have whetted your appetite for skygazing. Tonight is the main course though. On November 28, a young crescent Moon will join them posing next to the two bright planets above the western horizon at twilight. Much like tonight's visual feast, this night skyscape shows a young lunar crescent and brilliant Venus in the western evening twilight on October 29. The celestial beacons are setting over distant mountains and the Minya monastery, Ganzi Tibetan Autonomous Prefecture, Sichuan, China, planet Earth. Then Mercury, not Jupiter, was a celestial companion to Venus and the Moon. The fleeting innermost planet is just visible here in the bright twilight, below and left of Venus and near the center of the frame. Tomorrow, November 29, the crescent Moon will also help you spot planet Saturn for dessert.
Galileo's Europa Remastered (2019-11-29)
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, using improved new 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.
Star Trails for a Red Planet (2019-11-30)
Does Mars have a north star? In long exposures of Earth's night sky, star trails make concentric arcs around the north celestial pole, the direction of our fair planet's axis of rotation. Bright star Polaris is presently the Earth's North Star, close on the sky to Earth's north celestial pole. But long exposures on Mars show star trails too, concentric arcs about a celestial pole determined by Mars' axis of rotation. Tilted like planet Earth's, the martian axis of rotation points in a different direction in space though. It points to a place on the sky between stars in Cygnus and Cepheus with no bright star comparable to Earth's north star Polaris nearby. So even though this ruddy, weathered landscape is remarkably reminiscent of terrain in images from the  martian surface, the view must be from planet Earth, with north star Polaris near the center of concentric star trails. The landforms in the foreground are found in Qinghai Province in northwestern China.
Starburst Galaxy M94 from Hubble (2019-12-01)
Why does this galaxy have a ring of bright blue stars?  Beautiful island universe Messier 94 lies a mere 15 million light-years distant in the northern constellation of the Hunting Dogs (Canes Venatici). A popular target for Earth-based astronomers, the face-on spiral galaxy is about 30,000 light-years across, with spiral arms sweeping through the outskirts of its broad disk. But this Hubble Space Telescope field of view spans about 7,000 light-years across M94's central region. The featured close-up highlights the galaxy's compact, bright nucleus, prominent inner dust lanes, and the remarkable bluish ring of young massive stars. The ring stars are all likely less than 10 million years old, indicating that M94 is a starburst galaxy that is experiencing an epoch of rapid star formation from inspiraling gas. The circular ripple of blue stars is likely a wave propagating outward, having been triggered by the gravity and rotation of a oval matter distributions. Because M94 is relatively nearby, astronomers can better explore details of its starburst ring.    Astrophysicists: Browse 2,000+ codes in the Astrophysics Source Code Library
M27: The Dumbbell Nebula (2019-12-03)
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, the type of nebula our Sun will produce when nuclear fusion stops in its core. M27 is one of the brightest planetary nebulae on the sky, and can be seen toward the constellation of the Fox (Vulpecula) with binoculars. It takes light about 1000 years to reach us from M27, featured here in colors emitted by hydrogen and oxygen. Understanding the physics and significance of M27 was well beyond 18th century science. Even today, many things remain mysterious about bipolar planetary nebula like M27, including the physical mechanism that expels a low-mass star's gaseous outer-envelope, leaving an X-ray hot white dwarf.   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
Electric Night (2019-12-04)
It may appear, at first, like the Galaxy is producing the lightning, but really it's the Earth. The featured nighttime landscape was taken from a southern tip of the Italian Island of Sardinia in early June. The foreground rocks and shrubs are near the famous Capo Spartivento Lighthouse, and the camera is pointed south toward Algeria in Africa.  In the distance, across the Mediterranean Sea, a thunderstorm is threatening, with several electric lightning strokes caught together during this 25-second wide-angle exposure.  Much farther in the distance, strewn about the sky, are hundreds of stars in the neighborhood of our Sun in the Milky Way Galaxy. Farthest away, and slanting down from the upper left, are billions of stars that together compose the central band of our Milky Way.   Free Lecture: APOD editor to speak in NYC on January 3
Spiral Galaxy NGC 6744 (2019-12-05)
Beautiful spiral galaxy NGC 6744 is nearly 175,000 light-years across, larger than our own Milky Way. It lies some 30 million light-years distant in the southern constellation Pavo and appears as only a faint, extended object in small telescopes. We see the disk of the nearby island universe tilted towards our line of sight in this remarkably detailed galaxy portrait, a telescopic view that spans an area about the angular size of a full moon. In it, the giant galaxy's elongated yellowish core is dominated by the light from old, cool stars. Beyond the core, grand spiral arms are filled with young blue star clusters and speckled with pinkish star forming regions. An extended arm sweeps past a smaller satellite galaxy (NGC 6744A) at the lower right. NGC 6744's galactic companion is reminiscent of the Milky Way's satellite galaxy the Large Magellanic Cloud.
Pleiades to Hyades (2019-12-06)
This cosmic vista stretches almost 20 degrees from top to bottom, across the dusty constellation Taurus. It begins at the Pleiades and ends at the Hyades, two star clusters recognized since antiquity in Earth's night sky. At top, the compact Pleiades star cluster is about 400 light-years away. The lovely grouping of young cluster stars shine through dusty clouds that scatter blue starlight. At bottom, the V-shaped Hyades cluster looks more spread out in comparison and lies much closer, 150 light-years away. The Hyades cluster stars seem anchored by bright Aldebaran, a red giant star with a yellowish appearance. But Aldebaran actually lies only 65 light-years distant and just by chance along the line of sight to the Hyades cluster. Faint and darkly obscuring dust clouds found near the edge of the Taurus Molecular Cloud are also evident throughout the celestial scene. The wide field of view includes the dark nebula Barnard 22 at left with youthful star T Tauri and Hind's variable nebula just above Aldebaran in the frame.
Lines of Time (2019-12-07)
In time stars trace lines through the night sky on a rotating planet. Taken over two hours or more, these digitally added consecutive exposures were made with a camera and wide angle lens fixed to a tripod near Orel farm, Primorsky Krai, Russia, planet Earth. The stars trail in concentric arcs around the planet's south celestial pole below the scene's horizon, and north celestial pole off the frame at the upper right. Combined, the many short exposures also bring out the pretty star colours. Bluish trails are from stars hotter than Earth's Sun, while yellowish trails are from cooler stars. A long time ago this tree blossomed, but now reveals the passage of time in the wrinkled and weathered lines of its remains.