juliensimon/nasa-apod huggingface dataset:
Charon and the Small Moons of Pluto (2015-10-26)

What do the moons of Pluto look like? Before a decade ago, only the largest moon Charon was known, but never imaged. As the robotic New Horizons spacecraft was prepared and launched, other moons were identified on Hubble images but remained only specks of light. Finally, this past summer, New Horizons swept right past Pluto, photographed Pluto and Charon in detail, and took the best images of Styx, Nix, Kerberos, and Hydra that it could. The featured image composite shows the results -- each moon is seen to have a distinct shape, while underlying complexity is only hinted. Even though not satisfyingly resolved, these images are likely to be the best available to humanity for some time. This is because the moons are too small and distant for contemporary Earth-based telescopes to resolve, and no new missions to the Pluto system are planned.    Gallery: October's Venus, Jupiter, & Mars Conjunction
Bright from the Heart Nebula (2015-10-27)

What's that inside the Heart Nebula? First, the large emission nebula dubbed IC 1805 looks, in whole, like a human heart.  The nebula glows brightly in red light emitted by its most prominent element: hydrogen.  The red glow and the larger shape are all created by a small group of stars near the nebula's center.  In the center of the Heart Nebula are young stars from the open star cluster Melotte 15 that are eroding away several picturesque dust pillars with their energetic light and winds. The open cluster of stars contains a few bright stars nearly 50 times the mass of our Sun, many dim stars only a fraction of the mass of our Sun, and an absent microquasar that was expelled millions of years ago.  The Heart Nebula is located about 7,500 light years away toward the constellation of Cassiopeia.  At the top right is the companion Fishhead Nebula.

Image credit: Simon Addis
Massive Black Hole Shreds Passing Star (2015-10-28)

What happens when a star gets too close to a black hole? Recent observations from Earth-orbiting observatories of an event dubbed ASASSN-14li, in a distant galactic center, appears to be giving one star's harrowing story. Although angularly unresolved, variations in high energy light indicate that some of the star became shredded and reformed into a disk swirling around the dark abyss. In the hypothesized scenario envisioned, a jet formed on the spin axis of the black hole.  The innermost part of the disk, colored white, glows most strongly in X-rays and may drive a periodic wind, shown in blue.  Future X-ray and ultraviolet observations of stellar disruptions by black holes -- including those in the center of our own galaxy -- hold promise of telling us about the complex dynamics of some of the hottest and highest-gravity places in the universe.    Gallery: October's Venus, Jupiter, & Mars Conjunction
IC 1871: Inside the Soul Nebula (2015-10-29)

This cosmic close-up looks deep inside the Soul Nebula. The dark and brooding dust clouds outlined by bright ridges of glowing gas are cataloged as IC 1871. About 25 light-years across, the telescopic field of view spans only a small part of the much larger Heart and Soul nebulae. At an estimated distance of 6,500 light-years the star-forming complex lies within the Perseus spiral arm of the Milky Way, seen in planet Earth's skies toward the constellation Cassiopeia. An example of triggered star formation, the dense star-forming clouds of IC 1871 are themselves sculpted by the intense winds and radiation of the region's massive young stars. This color image adopts a palette made popular in Hubble images of star-forming regions.

Image credit: Sara Wager
The Witch Head Nebula (2015-10-30)

Double, double toil and trouble; Fire burn, and cauldron bubble .... maybe Macbeth should have consulted the Witch Head Nebula. A frighteningly shaped reflection nebula, this cosmic crone is about 800 light-years away though. Its malevolent visage seems to glare toward nearby bright star Rigel in Orion, just off the right edge of this frame. More formally known as IC 2118, the interstellar cloud of dust and gas is nearly 70 light-years across, its dust grains reflecting Rigel's starlight. In this composite portrait, the nebula's color is caused not only by the star's intense bluish light but because the dust grains scatter blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers in planet Earth's atmosphere are molecules of nitrogen and oxygen.

Image credit: Jeff
Signorelli
Ghosts and Star Trails (2015-10-31)

Don't be scared. Stars won't fall from the sky and ghosts won't really haunt your neighborhood tonight. But it looks like they might be doing just that in this eerie picture of an eccentric old abandoned house in moonlight. A treat for the eye the image is a trick of stacked multiple exposures, 60 frames exposed for 25 seconds each. While the digital frames were recorded with a camera fixed to a tripod, stars traced concentric arcs about the north celestial pole. But that's only a reflection of planet Earth's rotation on its axis. Conveniently marked by bright star Polaris, the pole could be positioned above the peaks of the deserted dwelling. Wrapped in a blanket to stay warm, the photographer's own movements during the exposures were blended into the ghostly apparitions. Of course, the grinning Jack-o-Lantern is there to wish you a safe and Happy Halloween!

Image credit: Chris Kotsiopoulos
The Milky Way Over Monument Valley (2015-11-01)

You don't have to be at Monument Valley to see the Milky Way arch across the sky like this -- but it helps. Only at Monument Valley USA would you see a picturesque foreground that includes these iconic rock peaks called buttes. Buttes are composed of hard rock left behind after water has eroded away the surrounding soft rock.  In the featured image taken in 2012, the closest butte on the left and the butte to its right are known as the Mittens, while Merrick Butte can be seen just further to the right. High overhead stretches a band of diffuse light that is the central disk of our spiral Milky Way Galaxy. The band of the Milky Way can be spotted by almost anyone on almost any clear night when far enough from a city and surrounding bright lights.   APOD in Spanish: On the web and Facebook

Image credit: Wally Pacholka
Comet ISON Being Destroyed by the Sun (2015-11-02)

Most comets don't survive a close encounter with the Sun. Two years ago this month, though, Comet ISON was thought by some to be big enough to withstand its perilous sungrazing dive. The featured video shows the drama as it was recorded by the Solar and Heliospheric Observatory (SOHO), a joint mission of ESA and NASA. As many Earthlings watched in fascination, a bright area did emerge from closest approach, but it soon faded and dispersed. It is now assumed that no large fragments of Comet C/2012 S1 (ISON) survived.  Besides the comet, the active Sun is seen to eject puffs of plasma known as coronal mass ejections. Launched in 1995, sun-orbiting SOHO has become a historic device in the discovery and tracking of comets known as sungrazers.  Two months ago, a comet designated SOHO 3000 was named in honor of the record 3000th comet that was discovered on SOHO images, a total that amounts to about half of all known comets.    Astrophysicists: Browse 1,100+ codes in the Astrophysics Source Code Library
Seeking Venus under the Spitzkoppe Arch (2015-11-03)

What's that in the sky? Although there was much to see in this spectacular panorama taken during the early morning hours of a day in late September, the brightest object in the sky was clearly the planet Venus. In the featured image, Venus was captured actually through a natural rock bridge, itself picturesque, in Spitzkoppe, Namibia. The planet, on the left of the opening, was complemented by a silhouette of the astrophotographer on the right. Above and beyond the rock bridge were many famous icons of a dark night sky, including, from left to right, the Pleiades star cluster, the Orion Nebula, the bright star Sirius, and the Large and Small Magellanic Clouds. This week, Venus remains visible to the east in the pre-dawn sky, being complemented by Mars, which is angularly quite close.

Image credit: Petr Hor�lek;
 Rollover Annotation:  Judy Schmidt
The Great Orion Nebula M42 (2015-11-04)

The Great Nebula in Orion, also known as M42, is one of the most famous nebulae in the sky. The star forming region's glowing gas clouds and hot young stars are on the right in this sharp and colorful image that includes the bluish reflection nebulae NGC 1977 and friends on the left. Located at the edge of an otherwise invisible giant molecular cloud complex, these eye-catching nebulas represent only a small fraction of this galactic neighborhood's wealth of interstellar material. Within the well-studied stellar nursery, astronomers have also identified what appear to be numerous infant planetary systems. The gorgeous skyscape spans nearly two degrees or about 45 light-years at the Orion Nebula's estimated distance of 1,500 light-years.

Image credit: Terry Hancock  
(Down Under Observatory)
NGC 1333: Stellar Nursery in Perseus (2015-11-05)

NGC 1333 is seen in visible light as a reflection nebula, dominated by bluish hues characteristic of starlight reflected by interstellar dust. A mere 1,000 light-years distant toward the heroic constellation Perseus, it lies at the edge of a large, star-forming molecular cloud. This striking close-up spans about two full moons on the sky or just over 15 light-years at the estimated distance of NGC 1333. It shows details of the dusty region along with hints of contrasting red emission from Herbig-Haro objects, jets and shocked glowing gas emanating from recently formed stars. In fact, NGC 1333 contains hundreds of stars less than a million years old, most still hidden from optical telescopes by the pervasive stardust. The chaotic environment may be similar to one in which our own Sun formed over 4.5 billion years ago.

Image credit: Agrupació
Astronòmica d'Eivissa/Ibiza (AAE)
Unraveling NGC 3169 (2015-11-06)

Spiral galaxy NGC 3169 appears to be unraveling in this cosmic scene, played out some 70 million light-years away just below bright star Regulus toward the faint constellation Sextans. Its beautiful spiral arms are distorted into sweeping tidal tails as NGC 3169 (top) and neighboring NGC 3166 interact gravitationally, a common fate even for bright galaxies in the local universe. In fact, drawn out stellar arcs and plumes, indications of gravitational interactions, seem rampant in the deep and colorful galaxy group photo. The picture spans 20 arc minutes, or about 400,000 light-years at the group's estimated distance, and includes smaller, dimmer NGC 3165 at bottom right. NGC 3169 is also known to shine across the spectrum from radio to X-rays, harboring an active galactic nucleus that is likely the site of a supermassive black hole.

Image credit: Warren Keller
Earth and Milky Way from Space (2015-11-07)

Since November 2000, people have been living continuously on the International Space Station. To celebrate humanity's 15th anniversary off planet Earth, consider this snapshot from space of our galaxy and our home world posing together beyond the orbital outpost. The Milky Way stretches below the curve of Earth's limb in the scene that also records a faint red, extended airglow. The galaxy's central bulge appears with starfields cut by dark rifts of obscuring interstellar dust. The picture was taken by Astronaut Scott Kelly on August 9, 2015, the 135th day of his one-year mission in space.
A Quadruple Sky Over Great Salt Lake (2015-11-08)

This was a sky to show the kids.  All in all, three children, three planets, the Moon, a star, an airplane and a mom were all captured in one image near Great Salt Lake in Utah, USA in early September of 2005.  Minus the airplane and the quadruple on the ground, this busy quadruple coincidence sky was visible last week all over the world.  The easiest object to spot is the crescent Moon, which is easily the brightest sky orb in the featured image.  Venus is the highest planet in the sky, with Jupiter to its right.  The bright star Spica completes the quadruple just below Venus.  The streak on the far right is an airplane.  Mom is seated.   Grandpa, appreciating the beauty of the moment, took the picture. This week, the pre-dawn sky shows a similar conjunction of planets.

Image credit: Michael Wilson
Assembly of The International Space Station (2015-11-09)

It is the largest and most sophisticated object ever built off the Earth.  It has taken numerous spaceflights and over a decade to construct. The International Space Station (ISS) is currently the premiere habitat for humans in Earth orbit, and an amalgamation of sophisticated orbiting laboratories that have examined everything from the formation of new materials and medicines created in microgravity -- to the limitations of the human body -- to the composition of the universe. This month, the ISS is celebrating 15 years of continuous human habitation. The ISS has been visited by astronauts from 15 countries, so far, and has international partners led by NASA (USA), Roscosmos (Russia), CSA (Canada), JAXA (Japan), and ESA (Europe).  The featured animation shows the piece-by-piece construction of the ISS from 1998 to 2011.  Spanning the length of a football field, the ISS can be seen as an unusually bright spot drifting slowly overhead by anyone who knows when and where to look.
AE Aurigae and the Flaming Star Nebula (2015-11-10)

Is star AE Aurigae on fire? No.  Even though AE Aurigae is named the flaming star, the surrounding nebula IC 405 is named the Flaming Star Nebula, and the region appears to have the color of fire, there is no fire.  Fire, typically defined as the rapid molecular acquisition of oxygen, happens only when sufficient oxygen is present and is not important in such high-energy, low-oxygen environments such as stars.  The material that appears as smoke is mostly interstellar hydrogen, but does contain smoke-like dark filaments of carbon-rich dust grains. The bright star AE Aurigae, visible toward the right near the nebula's center, is so hot it is blue, emitting light so energetic it knocks electrons away from surrounding gas. When a proton recaptures an electron, light is emitted, as seen in the surrounding emission nebula.  Pictured above, the Flaming Star nebula lies about 1,500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of the Charioteer (Auriga).   Follow APOD on: Facebook,  Google Plus, or Twitter

Image credit: Jes�s Vargas  
(Sky-Astrophotography) 
& Maritxu Poyal (Maritxu)
An Unexpected Rocket Plume over San Francisco (2015-11-11)

What is that unusual light in the sky? A common question, this particular light was not only bright but moving and expanding. It appeared just as the astrophotographer and his friend were photographing the Golden Gate Bridge in San Francisco, California against a more predictable night sky. They were not alone in seeing this unusual display -- at least hundreds of people in California reported a similar sight. The consensus of experienced sky observers was that the plume resulted from a rocket launch -- an explanation that was soon confirmed as an unpublicized test of a submarine-launched, unarmed, Trident II D5 nuclear missile. Such tests are not uncommon but do not usually occur just after sunset near a major metropolitan area -- when they are particularly noticeable to many people. Were plume images not posted to the Internet and quickly identified, such a sky spectacle might have been understood by some to be associated with more grandiose -- but incorrect -- explanations.

Image credit: Abe Blair  
(Abe Blair Gallery)
Kenya Morning Moon, Planets, and Taurid (2015-11-12)

On November 8, a waning crescent Moon joined the continuing parade of planets in Earth's early morning skies. Captured here from Amboseli National Park, Kenya, even the overexposed moonlight can't washout brilliant Venus though, lined up near the ecliptic plane with faint Mars and bright Jupiter above. As if Moon and planets aren't enough, a comparably bright Taurid meteor also streaks through the scene. In fact November's Taurid meteor showers have had a high proportion of bright fireballs. Apparently streaming from radiants in Taurus, the meteors are caused by our fair planet's annual passage through debris from Comet 2P/Encke. The comet's dust grains are catching up with Earth's atmosphere at a relatively low speed of about 27 kilometers per second.

Image credit: Babak Tafreshi
The Tadpoles of IC 410 (2015-11-13)

This telescopic close-up shows off the otherwise faint emission nebula IC 410. It also features two remarkable inhabitants of the cosmic pond of gas and dust below and right of center, the tadpoles of IC 410. Partly obscured by foreground dust, the nebula itself surrounds NGC 1893, a young galactic cluster of stars. Formed in the interstellar cloud a mere 4 million years ago, the intensely hot, bright cluster stars energize the glowing gas. Composed of denser cooler gas and dust, the tadpoles are around 10 light-years long and are likely sites of ongoing star formation. Sculpted by winds and radiation from the cluster stars, their heads are outlined by bright ridges of ionized gas while their tails trail away from the cluster's central region. IC 410 lies some 10,000 light-years away, toward the nebula-rich constellation Auriga.

Image credit: Steven Coates
Wright Mons on Pluto (2015-11-14)

Long shadows are cast by a low Sun across this rugged looking terrain. Captured by New Horizons, the scene is found just south of the southern tip Sputnik Planum, the informally named smooth, bright heart region of Pluto. Centered is a feature provisionally known as Wright Mons, a broad, tall mountain, about 150 kilometers across and 4 kilometers high, with a 56 kilometer wide, deep summit depression. Of course, broad mountains with central craters are found elsewhere in the Solar System, like Mauna Loa on planet Earth and Olympus Mons on Mars. In fact, New Horizons scientists announced the striking similarity of Pluto's Wright Mons, and nearby Piccard Mons, to large shield volcanoes strongly suggests the two could be giant cryovolcanoes that once erupted molten ice from the interior of the cold, distant world.
Leonids Over Monument Valley (2015-11-15)

There was a shower over Monument Valley -- but not water.  Meteors.  The featured image -- actually a composite of six exposures of about 30 seconds each -- was taken in 2001, a year when there was a very active Leonids shower. At that time, Earth was moving through a particularly dense swarm of sand-sized debris from Comet Tempel-Tuttle, so that meteor rates approached one visible streak per second. The meteors appear parallel because they all fall to Earth from the meteor shower radiant -- a point on the sky towards the constellation of the Lion (Leo). The yearly Leonids meteor shower peaks again this week. Although the Moon's glow should not obstruct the visibility of many meteors, this year's shower will peak with perhaps 15 meteors visible in an hour, a rate which is good but not expected to rival the 2001 Leonids.  By the way -- how many meteors can you identify in the featured image?

Image credit: Sean M. Sabatini
A Blazing Fireball between the Orion Nebula and Rigel (2015-11-16)

What's happening to that meteor? A few days ago, a bright fireball was photographed from the Alps mountain range in Switzerland as it blazed across the sky.  The fireball, likely from the Taurids meteor shower, was notable not only for how bright it was, but for the rare orange light it created that lingered for several minutes. Initially, the orange glow made it seem like the meteor trail was on fire.  However, the orange glow, known as a persistent train, originated neither from fire nor sunlight-reflecting smoke.  Rather, the persistent train's glow emanated from atoms in the Earth's atmosphere in the path of the meteor -- atoms that had an electron knocked away and emit light during reacquisition.  Persistent trains often drift, so that the long 3-minute exposure actually captured the initial wind-blown displacement of these bright former ions.  The featured image was acquired when trying to image the famous Orion Nebula, visible on the upper left.  The bright blue star Rigel, part of the constellation of Orion, is visible to the right. This week the fireball-rich Taurids meteor shower continues to be active even though it has passed its peak, while the more active Leonids meteor shower is just peaking.    Follow APOD on: Facebook,  Google Plus, or Twitter

Image credit: Ivo Scheggia
The Pelican Nebula in Gas, Dust, and Stars (2015-11-17)

The Pelican Nebula is slowly being transformed.  IC 5070, the official designation, is divided from the larger North America Nebula by a molecular cloud filled with dark dust.  The Pelican, however, receives much study because it is a particularly active mix of star formation and evolving gas clouds.  The featured picture was produced in three specific colors -- light emitted by sulfur, hydrogen, and oxygen --  that can help us to better understand these interactions.  The light from young energetic stars is slowly transforming the cold gas to hot gas, with the advancing boundary between the two, known as an ionization front, visible in bright orange on the right. Particularly dense tentacles of cold gas remain.  Millions of years from now this nebula might no longer be known as the Pelican, as the balance and placement of stars and gas will surely leave something that appears completely different.   Yearly Astronomy Review: APOD editor to speak in January in Philadelphia and New York City

Image credit: Roberto Colombari
A Sudden Jet on Comet 67P (2015-11-18)

There she blows!  A dramatic demonstration of how short-lived some comet jets can be was documented in late July by the robotic Rosetta spacecraft orbiting the nucleus of Comet 67P/Churyumov-Gerasimenko. The featured animation depicts changes in the rotating comet with three illuminating stills.  Although the first frame shows nothing unusual, the second frame shows a sudden strong jet shooting off the 67P's surface only 20 minutes later, while the third frame -- taken 20 minutes after that -- shows but a slight remnant of the once-active jet. As comets near the Sun, they can produce long and beautiful tails that stream across the inner Solar System.  How comet jets produce these tails is a topic of research -- helped by images like this. Another recent Rosetta measurement indicates that the water on Earth could not have come from comets like 67P because of significant differences in impurities.  Comet 67P spans about four kilometers, orbits the Sun between Earth and Jupiter, and has been the home for ESA's Rosetta spaceship since 2014 August. Rosetta is currently scheduled to make a slow crash onto Comet 67P's surface in late 2016.
Centaurus A (2015-11-19)

What's the closest active galaxy to planet Earth? That would be Centaurus A, only 11 million light-years distant. Spanning over 60,000 light-years, the peculiar elliptical galaxy is also known as NGC 5128. Forged in a collision of two otherwise normal galaxies, Centaurus A's fantastic jumble of young blue star clusters, pinkish star forming regions, and imposing dark dust lanes are seen here in remarkable detail. The colorful galaxy portrait is a composite of image data from space- and ground-based telescopes large and small. Near the galaxy's center, left over cosmic debris is steadily being consumed by a central black hole with a billion times the mass of the Sun. As in other active galaxies, that process generates the radio, X-ray, and gamma-ray energy radiated by Centaurus A.

Image credit: Robert Gendler,
Roberto Colombari

 Image Data: 
Hubble Space
Telescope,
European Southern Observatory