juliensimon/nasa-apod huggingface dataset:
NGC 6823: Cloud Sculpting Star Cluster (2014-10-08)

Star cluster NGC 6823 is slowly turning gas clouds into stars.  The center of the open cluster, visible on the upper right, formed only about two million years ago and is dominated in brightness by a host of bright young blue stars.  Some outer parts of the cluster, visible in the featured image's center as the stars and pillars of emission nebula NGC 6820, contain even younger stars.  The huge pillars of gas and dust likely get their elongated shape by erosion from hot radiation emitted from the brightest cluster stars.  Striking dark globules of gas and dust are also visible across the upper left of the featured image. Open star cluster NGC 6823 spans about 50 light years and lies about 6000 light years away toward the constellation of the Fox (Vulpecula).   APOD Wall Calendar: Nebulas and Star Clusters

Image credit: Donald P. Waid
(Waid Observatory)
Eclipse at Moonset (2014-10-09)

The Pacific Ocean and Chilean coast lie below this sea of clouds. Seen through the subtle colors of the predawn sky a lunar eclipse is in progress above, the partially eclipsed Moon growing dark. The curved edge of planet Earth's shadow still cuts across the middle of the lunar disk as the Moon sinks lower toward the western horizon. In fact, from this southern hemisphere location as well as much of eastern North America totality, the Moon completely immersed within Earth's shadow, began near the time of moonset and sunrise on October 8. From farther west the total phase could be followed for almost an hour though, the darker reddened Moon still high in the night sky.

Image credit: Yuri Beletsky
Moons at Opposition (2014-10-10)

From the early hours of October 8, over the Santa Cruz Mountains near Los Gatos, California, the totally eclipsed Moon shows a range of color across this well-exposed telescopic view of the lunar eclipse. Of course, a lunar eclipse can only occur when the Moon is opposite the Sun in Earth's sky and gliding through the planet's shadow. But also near opposition during this eclipse, and remarkably only half a degree or so from the lunar limb, distant Uranus is faint but easy to spot at the lower right. Fainter still are the ice giant's moons. To find them, slide your cursor over the image (or just follow this link) to check out a longer exposure. While even the darkened surface of our eclipsed Moon will be strongly overexposed, Uranus moons Titania, Oberon, and Umbriel can just be distinguished as faint pinpricks of light.

Image credit: Rick Baldridge
Eclipse at Moonrise (2014-10-11)

As the Moon rose and the Sun set on October 8, a lunar eclipse was in progress seen from Chongqing, China. Trailing through  this composite time exposure, the rising Moon began as a dark reddened disk in total eclipse near the eastern horizon. Steadily climbing above the populous city's colorful lights along the Yangtze River, the moontrail grows brighter and broader, until a bright Full Moon emerged from the Earth's shadow in evening skies. Although lunar eclipses are not always total ones, this eclipse, along with last April's lunar eclipse, were the first two of four consecutive total lunar eclipses, a series known as a tetrad. The final two eclipses of this tetrad will occur in early April and late September 2015.

Image credit: Zhou Yannan
The Helix Nebula from Blanco and Hubble (2014-10-12)

How did a star create the Helix nebula?  The shapes of planetary nebula like the Helix are important because they likely hold clues to how stars like the Sun end their lives.  Observations by the orbiting Hubble Space Telescope and the 4-meter Blanco Telescope in Chile, however, have shown the Helix is not really a simple helix.  Rather, it incorporates two nearly perpendicular disks as well as arcs, shocks, and even features not well understood.  Even so, many strikingly geometric symmetries remain.  How a single Sun-like star created such beautiful yet geometric complexity is a topic of research.  The Helix Nebula is the nearest planetary nebula to Earth, lies only about 700 light years away toward the constellation of Aquarius, and spans about 3 light-years.    APOD Wall Calendar: Nebulas and Star Clusters
Sprite Lightning in Slow Motion (2014-10-13)

What causes sprite lightning? Mysterious bursts of light in the sky that momentarily resemble gigantic jellyfish have been recorded for over 25 years, but their root cause remains unknown. Some thunderstorms have them -- most don't.  Recently, however, high speed videos are better detailing how sprites actually develop.  The featured video is fast enough -- at about 10,000 frames per second -- to time-resolve several sprite "bombs" dropping and developing into the multi-pronged streamers that appear on still images. Unfortunately, the visual clues provided by these videos do not fully resolve the sprite origins mystery. They do indicate to some researchers, though, that sprites are more likely to occur when plasma irregularities exist in the upper atmosphere.    Astrophysicists: Browse 900+ codes in the Astrophysics Source Code Library
Auroral Corona over Norway (2014-10-14)

Higher than the highest mountain lies the realm of the aurora.  Auroras rarely reach below 60 kilometers, and can range up to 1000 kilometers.  Aurora light results from energetic electrons and protons striking atoms and molecules in the Earth's atmosphere.  Somewhat uncommon, an auroral corona appears as a center point for a surrounding display and may occur when an aurora develops directly overhead, or when auroral rays are pointed nearly toward the observer.  This picturesque but brief green and purple aurora exhibition occurred last month high above Kval�ya, Troms�, Norway. The Sess�yfjorden fjord runs through the foreground, while numerous stars are visible far in the distance.   APOD Wall Calendar: Land and Skyscapes

Image credit: Harald Albrigtsen
Mysterious Changing feature on Titan (2014-10-15)

What is that changing object in a cold hydrocarbon sea of Titan? Radar images from the robotic Cassini spacecraft orbiting Saturn have been recording the surface of the cloud-engulfed moon Titan for years. When imaging the flat -- and hence radar dark -- surface of the methane and ethane lake called Ligeia Mare, an object appeared in 2013 just was not there in 2007. Subsequent observations in 2014 found the object remained -- but had changed! The featured image shows how the 20-km long object has appeared and evolved. Current origin speculative explanations include bubbling foam and floating solids, but no one is sure. Future observations may either resolve the enigma or open up more speculation.
Rosetta's Selfie (2014-10-16)

This Rosetta spacecraft selfie was snapped on October 7th. At the time the spacecraft was about 472 million kilometers from planet Earth, but only 16 kilometers from the surface of comet 67P/Churyumov-Gerasimenko. Looming beyond the spacecraft near the top of the frame, dust and gas stream away from the comet's curious double-lobed nucleus and bright sunlight glints off one of Rosetta's 14 meter long solar arrays. In fact, two exposures, one short and one long, were combined to record the dramatic high contrast scene using the CIVA camera system on Rosetta's still-attached Philae lander. Its chosen primary landing site is visible on the smaller lobe of the nucleus. This is the last image anticipated from Philae's cameras before the lander separates from Rosetta on November 12. Shortly after separation Philae will take another image looking back toward the orbiter, and begin its descent to the nucleus of the comet.
Messier 6 and Comet Siding Spring (2014-10-17)

This looks like a near miss but the greenish coma and tail of Comet Siding Spring (C/2013 A1) are really 2,000 light-years or so away from the stars of open cluster Messier 6. They do appear close together though, along the same line-of-sight in this gorgeous October 9th skyscape toward the constellation Scorpius. Still, on Sunday, October 19th this comet really will be involved in a near miss, passing within only 139,500 kilometers of planet Mars. That's about 10 times closer than any known comet flyby of planet Earth, and nearly one third the Earth-Moon distance. While an impact with the nucleus is not a threat the comet's dust, moving with a speed of about 56 kilometers per second relative to the Red Planet, and outskirts of its gaseous coma could interact with the thin Martian atmosphere. Of course, the comet's close encounter will be followed intently by spacecraft in Martian orbit and rovers on the surface.

Image credit: CARA Project
Melotte 15 in the Heart (2014-10-18)

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 toward the right 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 30 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: Ivan Eder
Comet McNaught Over New Zealand (2014-10-19)

Comet McNaught was perhaps the most photogenic comet of modern times -- from Earth.  After making quite a show in the northern hemisphere in early January of 2007, the comet moved south and developed a long and unusual dust tail that dazzled southern hemisphere observers. In late January 2007, Comet McNaught was captured between Mount Remarkable and Cecil Peak in this spectacular image taken from Queenstown, South Island, New Zealand.   The bright comet dominates the right part of the above image, while the central band of our Milky Way Galaxy dominates the left.  Careful inspection of the image will reveal a meteor streak just to the left of the comet.  Today, Comet Siding Spring may become the most photogenic comet of modern times -- from Mars.   Poll: How do you access APOD?

Image credit: Minoru Yoneto
Comet Siding Spring Passes Mars (2014-10-20)

Yesterday, a comet passed very close to Mars. In fact, Comet C/2013 A1 (Siding Spring) passed closer to the red planet than any comet has ever passed to Earth in recorded history. To take advantage of this unique opportunity to study the close interaction of a comet and a planet, humanity currently has five active spacecraft orbiting Mars: NASA's MAVEN, MRO, Mars Odyssey, as well as ESA's Mars Express, and India's Mars Orbiter. Most of these spacecraft have now sent back information that they have not been damaged by small pieces of the passing comet. These spacecraft, as well as the two active rovers on the Martian surface -- NASA's Opportunity and Curiosity -- have taken data and images that will be downloaded to Earth for weeks to come and likely studied for years to come.  The featured image taken yesterday, however, was not taken from Mars but from Earth and shows Comet Siding Spring on the lower left as it passed Mars, on the upper right.   NASA Updates : Comet Siding Spring from Mars

Image credit: SEN/Damian Peach
Mimas: Small Moon with a Big Crater (2014-10-21)

Whatever hit Mimas nearly destroyed it.  What remains is one of the largest impact craters on one of Saturn's smallest moons.  The crater, named Herschel after the 1789 discoverer of Mimas, Sir William Herschel, spans about 130 kilometers and is pictured above. Mimas' low mass produces a surface gravity just strong enough to create a spherical body but weak enough to allow such relatively large surface features. Mimas is made of mostly water ice with a smattering of rock - so it is accurately described as a big dirty snowball. The above image was taken during the 2010 February flyby of the robot spacecraft Cassini now in orbit around Saturn. A recent analysis of Mimas's unusual wobble indicates that it might house a liquid water interior ocean.   Follow APOD on: Facebook,  Google Plus, or Twitter
Sunspot Group AR 2192 Crackles (2014-10-22)

One of the largest sunspot groups in recent years is now crossing the Sun. Labelled Active Region 2192, it has already thrown a powerful solar flare and has the potential to produce more. The featured video shows a time lapse sequence of the Sun in visible and ultraviolet light taken yesterday and incorporating the previous 48 hours. AR 2192, rotating in from the left, rivals Jupiter in size and is literally crackling with magnetic energy.  The active Sun has caused some spectacular auroras in recent days, and energetic particles originating from AR 2192 may help continue them over the next week. Tomorrow, the Sun will appear unusual for even another reason: a partial solar eclipse will be visible before sunset from much of North America.
Galaxies in Pegasus (2014-10-23)

This wide, sharp telescopic view reveals galaxies scattered beyond the stars and faint dust nebulae of the Milky Way at the northern boundary of the high-flying constellation Pegasus. Prominent at the upper right is NGC 7331. A mere 50 million light-years away, the large spiral is one of the brighter galaxies not included in Charles Messier's famous 18th century catalog. The disturbed looking group of galaxies at the lower left is well-known as Stephan's Quintet. About 300 million light-years distant, the quintet dramatically illustrates a multiple galaxy collision, its powerful, ongoing interactions posed for a brief cosmic snapshot. On the sky, the quintet and NGC 7331 are separated by about half a degree.   Today: Partial Solar Eclipse

Image credit: AeW Observatory
AR 2192: Giant on the Sun (2014-10-24)

As you (safely!) watched the progress of yesterday's partial solar eclipse, you probably also spotted a giant sunspot group. Captured in this sharp telescopic image from October 22nd the complex AR 2192 is beautiful to see, a sprawling solar active region comparable in size to the diameter of Jupiter. Like other smaller sunspot groups, AR 2192 is now crossing the Earth-facing side of the Sun and appears dark in visible light because it is cooler than the surrounding surface. Still, the energy stored in the region's twisted magnetic fields is enormous and has already generated powerful explosions, including two X-class solar flares this week. Coronal mass ejections (CMEs) associated with the flares have not affected planet Earth, so far. The forecast for further activity from AR 2192 is still significant though, as it swings across the center of the solar disk and Earth-directed CMEs become possible.

Image credit: Randall Shivak
Sunspots and Solar Eclipse (2014-10-25)

A New Moon joined giant sunspot group AR 2192 to dim the bright solar disk during Thursday's much anticipated partial solar eclipse. Visible from much of North America, the Moon's broad silhouette is captured in this extreme telephoto snapshot near eclipse maximum from Santa Cruz, California. About the size of Jupiter, the remarkable AR 2192 itself darkens a noticeable fraction of the Sun, near center and below the curved lunar limb. As the sunspot group slowly rotates across the Sun and out of view in the coming days its activity is difficult to forecast. But the timing of solar eclipses is easier to predict. The next will be a total solar eclipse on March 20, 2015.

Image credit: Michael Bolte (UCSC)
Too Close to a Black Hole (2014-10-26)

What would you see if you went right up to a black hole? Featured is a computer generated image highlighting how strange things would look. The black hole has such strong gravity that light is noticeably bent towards it - causing some very unusual visual distortions. Every star in the normal frame has at least two bright images - one on each side of the black hole. Near the black hole, you can see the whole sky - light from every direction is bent around and comes back to you. The original background map was taken from the 2MASS infrared sky survey, with stars from the Henry Draper catalog superposed.  Black holes are thought to be the densest state of matter, and there is indirect evidence for their presence in stellar binary systems and the centers of globular clusters, galaxies, and quasars.   Gallery: Thursday's Partial Solar Eclipse

Image credit: Alain Riazuelo
Plane, Clouds, Moon, Spots, Sun (2014-10-27)

What's that in front of the Sun?  The closest object is an airplane, visible just below the Sun's center and caught purely by chance.  Next out are numerous clouds in Earth's atmosphere, creating a series of darkened horizontal streaks. Farther out is Earth's Moon, seen as the large dark circular bite on the upper right. Just above the airplane and just below the Sun's surface are sunspots. The main sunspot group captured here, AR 2192, is one of the largest ever recorded and has been crackling and bursting with flares since it came around the edge of the Sun early last week. Taken last Thursday, this show of solar silhouettes was unfortunately short-lived.  Within a few seconds the plane flew away. Within a few minutes the clouds drifted off. Within a few hours the partial solar eclipse of the Sun by the Moon was over. Only the sunspot group remains, but within a few more days even AR 2192 will disappear around the edge of the Sun. Fortunately, when it comes to the Sun, even unexpected alignments are surprisingly frequent.   Gallery: Last Thursday's Partial Solar Eclipse

Image credit: Doyle and
Shannon Slifer
Retrograde Mars (2014-10-28)

Why would Mars appear to move backwards?  Most of the time, the apparent motion of Mars in Earth's sky is in one direction, slow but steady in front of the far distant stars. About every two years, however, the Earth passes Mars as they orbit around the Sun.  During the most recent such pass starting late last year, Mars as usual, loomed large and bright.  Also during this time, Mars appeared to move backwards in the sky, a phenomenon called retrograde motion.  Featured here is a series of images digitally stacked so that all of the stars coincide.  Here, Mars appears to trace out a narrow loop in the sky.  At the center of the loop, Earth passed Mars and the retrograde motion was the highest.  Retrograde motion can also be seen for other Solar System planets.   APOD Wall Calendar: Moons and Planets

Image credit: Tunç Tezel
Iridescent Cloud Edge Over Colorado (2014-10-29)

Sometimes your eclipse viewing goes bad in an interesting way. While watching and photographing last Thursday's partial solar eclipse, a popular astronomy blogger suffered through long periods of clouds blocking the Sun. Unexpectedly, however, a nearby cloud began to show a rare effect: iridescence.  Frequently part of a more familiar solar corona effect, iridescence is the diffraction of sunlight around a thin screen of nearly uniformly-sized water droplets.  Different colors of the sunlight become deflected by slightly different angles and so come to the observer from slightly different directions.  This display, featured here, was quite bright and exhibited an unusually broad range of colors. On the right, the contrails of an airplane are also visible.    APOD Wall Calendar:  Weather and Volcanoes

Image credit: Phil Plait 
(Bad Astronomy Blog, 
Slate)
A Spectre in the Eastern Veil (2014-10-30)

Frightening forms and scary faces are a mark of the Halloween season. They also haunt 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 in the constellation Cygnus, this portion of the eastern Veil 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 atoms in blue-green hues. Of course, in the western part of the Veil lies another seasonal apparition, the Witch's Broom.

Image credit: Ken Crawford
Milky Way over Devils Tower (2014-10-31)

A mysterious formation known as Devils Tower rises into the dark above northeastern Wyoming's prairie landscape in this 16 frame panoramic view. Seen against the night sky's thin, pale clouds and eerie green airglow, star clusters and nebulae of the Milky Way arc toward the galaxy's central realm at right. Of course the scene contains the Milky Way's own haunting and grisly visages of halloween, including ghosts, a flaming skull, a glowing eye and a witch's broom. To find them, slide your cursor over the picture or just follow this link, if you dare. And have a safe and Happy Halloween!

Image credit: David Lane
The Day After Mars (2014-11-01)

October 31, 1938 was the day after Martians encountered planet Earth, and everything was calm. Reports of the invasion were revealed to be part of a Halloween radio drama, the now famous broadcast based on H.G. Wells' scifi novel War of the Worlds. On Mars October 20, 2014 was calm too, the day after its close encounter with Comet Siding Spring. Not a hoax, this comet really did come within 86,700 miles or so of Mars, about 1/3 the Earth-Moon distance. Earth's spacecraft and rovers in Mars orbit and on the surface reported no ill effects though, and had a ringside seat as a visitor from the outer solar system passed by. Spanning over 2 degrees against stars of the constellation Ophiuchus, this colorful telescopic snapshot captures our view of Mars on the day after. Bluish star 51 Ophiuchi is at the upper right and the comet is just emerging from the Red Planet's bright glare.

Image credit: CARA Project
Titan Beyond the Rings (2014-11-02)

When orbiting Saturn, be sure to watch for breathtaking superpositions of moons and rings.  One such picturesque vista was visible recently to the robot Cassini spacecraft now orbiting Saturn.  In 2006 April, Cassini captured Saturn's A and F rings stretching in front of cloud-shrouded Titan.  Near the rings and appearing just above Titan was Epimetheus, a moon which orbits just outside the F ring. The dark space in the A ring is called the Encke Gap, although several thin knotted ringlets and even the small moon Pan orbit there.   APOD Wall Calendar:  Moons and Planets
In Green Company: Aurora over Norway (2014-11-03)

Raise your arms if you see an aurora. With those instructions, two nights went by with, well, clouds -- mostly. On the third night of returning to same peaks, though, the sky not only cleared up but lit up with a spectacular auroral display. Arms went high in the air, patience and experience paid off, and the amazing featured image was captured. The setting is a summit of the Austnesfjorden fjord close to the town of Svolvear on the Lofoten islands in northern Norway. The time was early March. Our Sun has been producing an abundance of picturesque aurora of late as it is near the time of its maximum surface activity in its 11-year magnetic cycle.

Image credit: Max Rive
Moon and Earth from Chang'e 5-T1 (2014-11-04)

Described at times as a big blue marble, from some vantage points Earth looks more like a small blue marble. Such was the case in this iconic image of the Earth and Moon system taken by the Chang'e 5-T1 mission last week. The Moon appears larger than the Earth because it was much closer to the spacecraft's camera. Displaying much of a surface usually hidden from Earth, the Moon appears dark and gray when compared to the more reflective and colorful planet that it orbits.  The robotic Chang'e 5-T1 spacecraft, predominantly on an engineering test mission, rounded the Moon last Tuesday returned to Earth on Friday.