juliensimon/nasa-apod huggingface dataset:
The Heart and Soul Nebulas (2019-01-15)

Is the heart and soul of our Galaxy located in Cassiopeia?  Possibly not, but that is where two bright emission nebulas nicknamed Heart and Soul can be found.  The Heart Nebula, officially dubbed IC 1805 and visible in the featured image on the bottom right, has a shape reminiscent of a classical heart symbol.  The Soul Nebula is officially designated IC 1871 and is visible on the upper left. Both nebulas shine brightly in the red light of energized hydrogen. Also shown in this three-color montage is light emitted from sulfur, shown in yellow, and oxygen, shown in blue.  Several young open clusters of stars are visible near the nebula centers.  Light takes about 6,000 years to reach us from these nebulas, which together span roughly 300 light years.  Studies of stars and clusters like those found in the Heart and Soul Nebulas have focused on how massive stars form and how they affect their environment.   Follow APOD on: Instagram, Facebook,  Reddit, or Twitter

Image credit: Mario Zauner
IC 342: The Hidden Galaxy (2019-01-16)

Similar in size to large, bright spiral galaxies in our neighborhood, IC 342 is a mere 10 million light-years distant in the long-necked, northern constellation Camelopardalis. A sprawling island universe, IC 342 would otherwise be a prominent galaxy in our night sky, but it is hidden from clear view and only glimpsed through the veil of stars, gas and dust clouds along the plane of our own Milky Way galaxy. Even though IC 342's light is dimmed and reddened by intervening cosmic clouds, this sharp telescopic image traces the galaxy's own obscuring dust, young star clusters, and glowing pink star forming regions along spiral arms that wind far from the galaxy's core. IC 342 may have undergone a recent burst of star formation activity and is close enough to have gravitationally influenced the evolution of the local group of galaxies and the Milky Way.

Image credit: Arturas Medvedevas
Cabin under the Stars (2019-01-17)

Gocka's, a family nickname for the mountain cabin, and a wooden sled from a generation past stand quietly under the stars. The single exposure image was taken on January 6 from Tanndalen Sweden to evoke a simple visual experience of the dark mountain skies. A pale band of starlight along the Milky Way sweeps through the scene. At the foot of Orion the Hunter, bright star Rigel shines just above the old kicksled's handrail. Capella, alpha star of Auriga the celestial charioteer, is the brightest star at the top of the frame. In fact, the familiar stars of the winter hexagon and the Pleiades star cluster can all be found in this beautiful skyscape from a northern winter night.

Image credit: Clear Skies
Circumpolar Star Trails (2019-01-18)

As Earth spins on its axis, the stars appear to rotate around an observatory in this well-composed image from the Canary Island of Tenerife. Of course, the colorful concentric arcs traced out by the stars are really centered on the planet's North Celestial Pole. Convenient for northern hemisphere astro-imagers and celestial navigators alike, bright star Polaris is near the pole and positioned in this scene to be behind the telescope dome. Made with a camera fixed to a tripod, the series of over 200 stacked digital exposures spanned about 4 hours. The observatory was not operating on that clear, dark night, but that's not surprising. The dome houses the Teide Observatory's large THEMIS Solar Telescope.

Image credit: Gabriel Funes
Total Lunar Eclipse at Moonset (2019-01-19)

The Moon slid through Earth's shadow on January 31, 2018 in a total lunar eclipse. In this time-lapse sequence of that eclipse from Portal, Arizona, USA, the partial eclipse starts with the Moon high in the western sky. The eclipse total phase lasted about 76 minutes, but totality ended after the dark, reddened Moon set below the horizon. The upcoming total lunar eclipse, on the night of January 20/21, will be better placed for skygazers across the Americas, though. There, all 62 minutes of the total phase, when the Moon is completely immersed in Earth's dark umbral shadow, will take place with the Moon above the horizon. Watch it if you can. The next total lunar eclipse visible from anywhere on planet Earth won't take place until May 26, 2021, and then the total eclipse will last a mere 15 minutes.

Image credit: MrEclipse.com
A Total Lunar Eclipse Video (2019-01-20)

Tonight a bright full Moon will fade to red. Tonight's moon will be particularly bright because it is reaching its fully lit phase when it is relatively close to the Earth in its elliptical orbit.  In fact, by some measures of size and brightness, tonight's full Moon is designated a supermoon, although perhaps the "super" is overstated because it will be only a few percent larger and brighter than the average full Moon. However, our Moon will fade to a dim red because it will also undergo a total lunar eclipse -- an episode when the Moon becomes completely engulfed in Earth's shadow. The faint red color results from blue sunlight being more strongly scattered away by the Earth's atmosphere. A January full moon, like the one visible tonight, is referred to as a Wolf Moon in some cultures.  Tonight's supermoon total eclipse will last over an hour and be best visible from North and South America after sunset.  The featured time-lapse video shows the last total lunar eclipse -- which occurred in 2018 July. The next total lunar eclipse will occur only in 2021 May.

Image credit: Jun Ho Oh (KAIST, 
HuboLab),
Kwon O Chul 
(TWAN), 
Jeong ByoungJun (RainbowAstro)
InSight Lander Takes Selfie on Mars (2019-01-21)

This is what NASA's Insight lander looks like on Mars. With its solar panels, InSight is about the size of a small bus.  Insight successfully landed on Mars in November with a main objective to detect seismic activity. The featured selfie is a compilation of several images taken of different parts of the InSight lander, by the lander's arm, at different times. SEIS, the orange-domed seismometer seen near the image center last month, has now been placed on the Martian surface.  With this selfie, Mars InSight continues  a long tradition of robotic spacecraft on Mars taking and returning images of themselves, including Viking, Sojourner, Pathfinder, Spirit, Opportunity, Phoenix, and Curiosity.  Data taken by Mars Insight is expected to give humanity unprecedented data involving the interior of Mars, a region thought to harbor formation clues not only about Mars, but Earth.    Growing Gallery:  Last Night's Total Lunar Eclipse
Lunar Eclipse over Cologne Cathedral (2019-01-22)

Why would a bright full Moon suddenly become dark?  Because it entered the shadow of the Earth.  That's what happened Sunday night as the Moon underwent a total lunar eclipse.  Dubbed by some as a Super (because the Moon was angularly larger than usual, at least slightly) Blood (because the scattering of sunlight through the Earth's atmosphere makes an eclipsed Moon appeared unusually red) Wolf (because January full moons are sometimes called Wolf Moons from the legend that wolves like to howl at the moon) Moon Eclipse, the shadowy spectacle was visible from the half of the Earth then facing the Moon, and was captured in numerous spectacular photographs.  Featured, a notable image sequence was captured over the Cologne Cathedral, a UNESCO World Heritage Site, in Cologne, Germany. The lunar eclipse sequence was composed from 68 different exposures captured over three hours during freezing temperatures -- and later digitally combined and edited to remove a cyclist and a pedestrian.  The next total lunar eclipse will occur in 2021.    Gallery:  Sunday Night's Total Lunar Eclipse

Image credit: Martin Junius
Orion over the Austrian Alps (2019-01-23)

Do you recognize this constellation? Through the icicles and past the mountains is Orion, one of the most identifiable star groupings on the sky and an icon familiar to humanity for over 30,000 years. Orion has looked pretty much the same during the past 50,000 years and should continue to look the same for many thousands of years into the future.  Orion is quite prominent in the sky this time of year, a recurring sign of (modern) winter in Earth's northern hemisphere and summer in the south. Pictured, Orion was captured recently above the Austrian Alps in a composite of seven images taken by the same camera in the same location during the same night. Below and slightly to the right of Orion's three-star belt is the Orion Nebula, while the four bright stars surrounding the belt are, clockwise from the upper left, Betelgeuse, Bellatrix, Rigel, and Saiph.    New: Instagram page features cool images recently submitted to APOD

Image credit: Luk� Vesel�
Matterhorn, Moon, and Meteor (2019-01-24)

Fans of planet Earth probably recognize the Matterhorn in the foreground of this night skyscape. Famed in mountaineering history, the 4,478 meter Alpine mountain stands next to the totally eclipsed Moon. In spite of -22 degree C temperatures, the inspired scene was captured on the morning of January 21 from the mountains near Zermatt, Switzerland. Different exposures record the dim red light reflected by the Moon fully immersed in Earth's shadow. Seen directly above the famous Alpine peak, but about 600 light-years away, are the stars of the Praesepe or Beehive star cluster also known as Messier 44. An added reward to the cold eclipse vigil, a bright and colorful meteor flashed below the temporarily dimmmed Moon, just tracing the Matterhorn's north-eastern climbing route along Hornli ridge.

Image credit: Stephane Vetter
Moon Struck (2019-01-25)

Craters produced by ancient impacts on the airless Moon have long been a familiar sight. But only since the 1990s have observers began to regularly record and study optical flashes on the lunar surface, likely explosions resulting from impacting meteoroids. Of course, the flashes are difficult to see against a bright, sunlit lunar surface. But during the January 21 total eclipse many imagers serendipitously captured a meteoroid impact flash against the dim red Moon. Found while examining images taken shortly before the total eclipse phase began, the flash is indicated in the inset above, near the Moon's darkened western limb. Estimates based on the flash duration recorded by the Moon Impact Detection and Analysis System (MIDAS) telescopes in southern Spain indicate the impactor's mass was about 10 kilograms and created a crater between seven and ten meters in diameter.

Image credit: Petr Horálek
The Umbra of Earth (2019-01-26)

The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, it has a circular cross section most easily seen during a lunar eclipse. For example, on January 21 the Full Moon slid across the northern half of Earth's umbral shadow, entertaining moonwatchers around much of the planet. In the total phase of the eclipse, the Moon was completely within the umbra for 63 minutes. Recorded under clear, dark skies from the hills near Chiuduno, Italy this composite eclipse image uses successive pictures from totality (center) and partial phases to trace out a large part of the umbra's curved edge. Reflecting sunlight scattered by the atmosphere into Earth's shadow, the lunar surface appears reddened during totality. But close to the umbra's edge, the limb of the eclipsed Moon shows a distinct blue hue. The blue eclipsed moonlight originates as rays of sunlight pass through layers high in the upper stratosphere, colored by ozone that scatters red light and transmits blue.

Image credit: Antonio
Finazzi
From the Northern to the Southern Cross (2019-01-27)

There is a road that connects the Northern to the Southern Cross but you have to be at the right place and time to see it. The road, as pictured here, is actually the central band of our Milky Way Galaxy; the right place, in this case, is dark Laguna Cejar in Salar de Atacama of Northern Chile; and the right time was in early October, just after sunset. Many sky wonders were captured then, including the bright Moon, inside the Milky Way arch;  Venus, just above the Moon; Saturn and Mercury, just below the Moon; the Large and Small Magellanic Clouds satellite galaxies, on the far left; red airglow near the horizon on the image left; and the lights of small towns at several locations across the horizon.  One might guess that composing this 30-image panorama would have been a serene experience, but for that one would have required earplugs to ignore the continued brays of wild donkeys.

Image credit: Nicholas
Buer
The Long Gas Tail of Spiral Galaxy D100 (2019-01-28)

Why is there long red streak attached to this galaxy?  The streak is made mostly of glowing hydrogen that has been systematically stripped away as the galaxy moved through the ambient hot gas in a cluster of galaxies.  Specifically, the galaxy is spiral galaxy D100, and cluster is the Coma Cluster of galaxies.  The red path connects to the center of D100 because the outer gas, gravitationally held less strongly, has already been stripped away by ram pressure. The extended gas tail is about 200,000 light-years long, contains about 400,000 times the mass of our Sun, and stars are forming within it.  Galaxy D99, visible to D100's lower left, appears red because it glows primarily from the light of old red stars -- young blue stars can no longer form because D99 has been stripped of its star-forming gas. The featured false-color picture is a digitally enhanced composite of images from Earth-orbiting Hubble and the ground-based Subaru telescope. Studying remarkable systems like this bolsters our understanding of how galaxies evolve in clusters.

Image credit: NASA, 
ESA, 
Hubble, 
Subaru Telescope, 
W. Cramer 
(Yale) 
et al., 
M. Yagi, 
J. DePasquale
Ultima Thule from New Horizons (2019-01-29)

How do distant asteroids differ from those near the Sun?  To help find out, NASA sent the robotic New Horizons spacecraft past the classical Kuiper belt object 2014 MU69, nicknamed Ultima Thule, the farthest asteroid yet visited by a human spacecraft.  Zooming past the 30-km long space rock on January 1, the featured image is the highest resolution picture of Ultima Thule's surface beamed back so far. Ultima Thule does look different from imaged asteroids of the inner Solar System, as it shows unusual surface texture, relatively few obvious craters, and nearly spherical lobes. Its shape is hypothesized to have formed from the coalescence of early Solar System rubble in into two objects -- Ultima and Thule -- which then spiraled together and stuck.  Research will continue into understanding the origin of different surface regions on Ultima Thule, whether it has a thin atmosphere, how it obtained its red color, and what this new knowledge of the ancient Solar System tells us about the formation of our Earth.
Wide Field View of Great American Eclipse (2019-01-30)

Only in the fleeting darkness of a total solar eclipse is the light of the solar corona easily visible. Normally overwhelmed by the bright solar disk, the expansive corona, the sun's outer atmosphere, is an alluring sight. But the subtle details and extreme ranges in the corona's brightness, although discernible to the eye, are notoriously difficult to photograph. Pictured here, however, using over 120 images and meticulous digital processing, is a detailed wide-angle image of the Sun's corona taken during the Great American Eclipse in 2017 August.  Clearly visible are intricate layers and glowing caustics of an ever changing mixture of hot gas and magnetic fields. Hundreds of stars as faint as 11th magnitude are visible behind the Moon and Sun, with Mars appearing in red on the far right.  The next total eclipse of the Sun will occur on July 2 and be visible during sunset from a thin swath across Chile and Argentina.

Image credit: Nicolas Lefaudeux
Sharpless 308: Star Bubble (2019-01-31)

Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as Sharpless 2-308 it lies some 5,200 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a Full Moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured in the expansive image is dominated by the glow of ionized oxygen atoms mapped to a blue hue. SH2-308 is also known as The Dolphin Nebula.

Image credit: Laubing
Twin Galaxies in Virgo (2019-02-01)

Spiral galaxy pair NGC 4567 and NGC 4568 share this sharp cosmic vista with lonely elliptical galaxy NGC 4564. All are members of the large Virgo Galaxy Cluster. With their classic spiral arms, dust lanes, and star clusters, the eye-catching spiral pair is also known as the Butterfly Galaxies. Very close together, the galaxy twins don't seem to be too distorted by gravitational tides. Their giant molecular clouds are known to be colliding though and are likely fueling the formation of massive star clusters. The galaxy twins are about 52 million light-years distant, while their bright cores appear separated by about 20,000 light-years. Of course, the spiky foreground stars lie within our own Milky Way.

Image credit: CHART32 Team
LDN 1622: Dark Nebula in Orion (2019-02-02)

The silhouette of an intriguing dark nebula inhabits this cosmic scene. Lynds' Dark Nebula (LDN) 1622 appears against a faint background of glowing hydrogen gas only easily seen in long telescopic exposures of the region. LDN 1622 lies near the plane of our Milky Way Galaxy, close on the sky to Barnard's Loop, a large cloud surrounding the rich complex of emission nebulae found in the Belt and Sword of Orion. But the obscuring dust of LDN 1622 is thought to be much closer than Orion's more famous nebulae, perhaps only 500 light-years away. At that distance, this 1 degree wide field of view would span less than 10 light-years. Its foreboding appearance lends this dark expanse a popular name, the Boogeyman Nebula.

Image credit: Tapio Lahtinen
An Airglow Fan from Lake to Sky (2019-02-03)

Why would the sky look like a giant fan? Airglow. The featured intermittent green glow appeared to rise from a lake through the arch of our Milky Way Galaxy, as captured during 2015 next to Bryce Canyon in Utah, USA.  The unusual pattern was created by atmospheric gravity waves, ripples of alternating air pressure that can grow with height as the air thins, in this case about 90 kilometers up.  Unlike auroras powered by collisions with energetic charged particles and seen at high latitudes, airglow is due to chemiluminescence, the production of light in a chemical reaction.  More typically seen near the horizon, airglow keeps the night sky from ever being completely dark.   Follow APOD on: Instagram, Facebook,  Reddit, or Twitter

Image credit: Dave Lane;
 Rollover Annotation:  Judy Schmidt
Henize 70: A Superbubble in the LMC (2019-02-04)

Massive stars profoundly affect their galactic environments.  Churning and mixing interstellar clouds of gas and dust, stars -- most notably those upwards of tens of times the mass of our Sun -- leave their mark on the compositions and locations of future generations of stars.  Dramatic evidence of this is illustrated in our neighboring galaxy, the Large Magellanic Cloud (LMC), by the featured nebula, Henize 70 (also known as N70 and DEM301).  Henize 70 is actually a luminous superbubble of interstellar gas about 300 light-years in diameter, blown by winds from hot, massive stars and supernova explosions, with its interior filled with tenuous hot and expanding gas.  Because superbubbles can expand through an entire galaxy, they offer humanity a chance to explore the connection between the lifecycles of stars and the evolution of galaxies.

Image credit: Josep M. Drudis
Perijove 16: Passing Jupiter (2019-02-05)

Watch Juno zoom past Jupiter again.  NASA's robotic spacecraft Juno is continuing on its 53-day, highly-elongated orbits around our Solar System's largest planet.  The featured video is from perijove 16, the sixteenth time that Juno has passed near Jupiter since it arrived in mid-2016. Each perijove passes near a slightly different part of Jupiter's cloud tops.  This color-enhanced video has been digitally composed from 21 JunoCam still images, resulting in a 125-fold time-lapse. The video begins with Jupiter rising as Juno approaches from the north. As Juno reaches its closest view -- from about 3,500 kilometers over Jupiter's cloud tops -- the spacecraft captures the great planet in tremendous detail. Juno passes light zones and dark belt of clouds that circle the planet, as well as numerous swirling circular storms, many of which are larger than hurricanes on Earth.  As Juno moves away, the remarkable dolphin-shaped cloud is visible.  After the perijove, Jupiter recedes into the distance, now displaying the unusual clouds that appear over Jupiter's south.  To get desired science data, Juno swoops so close to Jupiter that its instruments are exposed to very high levels of radiation.
Moon and Venus Appulse over a Tree (2019-02-06)

What's that bright spot near the Moon? Venus. About a week ago, Earth's Moon appeared unusually close to the distant planet Venus, an angular coincidence known as an appulse. Similar to a conjunction, which is a coordinate term, an appulse refers more generally to when two celestial objects appear close together. This Moon and Venus appulse -- once as close as 0.05 degrees -- was captured rising during the early morning behind Koko crater on the island of O'ahu in Hawaii, USA. The Moon was in a crescent phase with its lower left reflecting direct sunlight, while the rest of the Moon is seen because of Earthshine, sunlight first reflected from the Earth.  Some leaves and branches of a foreground kiawe tree are seen in silhouette in front of the bright crescent, while others, in front of a darker background, appear white because of forward scattering.  Appulses involving the Moon typically occur several times a year: for example the Moon is expected to pass within 0.20 degrees of distant Saturn on March 1.

Image credit: Alex Dzierba
Fox Fur, Unicorn, and Christmas Tree (2019-02-07)

Clouds of glowing hydrogen gas fill this colorful skyscape in the faint but fanciful constellation Monoceros, the Unicorn. A star forming region cataloged as NGC 2264, the complex jumble of cosmic gas and dust is about 2,700 light-years distant and mixes reddish emission nebulae excited by energetic light from newborn stars with dark interstellar dust clouds. Where the otherwise obscuring dust clouds lie close to the hot, young stars they also reflect starlight, forming blue reflection nebulae. The telescopic image spans about 3/4 degree or nearly 1.5 full moons, covering 40 light-years at the distance of NGC 2264. Its cast of cosmic characters includes the the Fox Fur Nebula, whose dusty, convoluted pelt lies near the top, bright variable star S Monocerotis immersed in the blue-tinted haze near center, and the Cone Nebula pointing in from the right side of the frame. Of course, the stars of NGC 2264 are also known as the Christmas Tree star cluster. The triangular tree shape is seen on its side here. Traced by brighter stars it has its apex at the Cone Nebula. The tree's broader base is centered near S Monocerotis.

Image credit: Stanislav Volskiy