juliensimon/nasa-apod huggingface dataset:
Sungrazer (2013-10-27)

Arcing toward a fiery fate, this Sungrazer comet was recorded by the SOHO spacecraft's Large Angle Spectrometric COronagraph(LASCO) on December 23, 1996. LASCO uses an occulting disk, partially visible at the lower right, to block out the otherwise overwhelming solar disk allowing it to image the inner 8 million kilometers of the relatively faint corona. The comet is seen as its coma enters the bright equatorial solar wind region (oriented vertically). Positioned in space to continuously observe the Sun, SOHO has now been used to discover over 1,500 comets, including numerous sungrazers. Based on their orbits, the vast majority of sungrazers are believed to belong to the Kreutz family of sungrazing comets created by successive break ups from a single large parent comet that passed very near the Sun in the twelfth century. The Great Comet of 1965, Ikeya-Seki, was also a member of the Kreutz family, coming within about 650,000 kilometers of the Sun's surface. Passing so close to the Sun, Sungrazers are subjected to destructive tidal forces along with intense solar heat. This small comet, known as the Christmas Comet SOHO 6, did not survive. Later this year, Comet ISON, potentially the brightest sungrazer in recorded history but not a Kreutz sungrazer, is expected to survive.
The Great Comet of 1680 Over Rotterdam (2013-10-28)

Was there ever another comet like ISON? Although no two comets are exactly alike, one that appears to have had notable similarities was Comet Kirch, the Great Comet of 1680. Like approaching Comet ISON, Comet Kirch was a bright sungrazer, making a very close approach to the surface of the Sun.  Neither comet, coincidently, is a member of the most common group of sungrazers -- the Kreutz group -- populated by remnants of a comet that disintegrated near the Sun hundreds of years ago.  The long tail of Comet Kirch is depicted in the above painting by Lieve Versheier. As pictured, some members of the foreground crowd of Rotterdam in the Netherlands are holding cross-staffs, an angle measuring device that predated the sextant. No one knows how Comet ISON will develop, but like Comet Kirch, it is expected to be brightest when very near the Sun, in ISON's case during last few days of November.   Gallery: Bright Comets of 2013
Horsehead and Orion Nebulas (2013-10-29)

The dark Horsehead Nebula and the glowing Orion Nebula are contrasting cosmic vistas. Adrift 1,500 light-years away in one of the night sky's most recognizable constellations, they appear in opposite corners of the above stunning mosaic. The familiar Horsehead nebula appears as a dark cloud, a small silhouette notched against the long red glow at the lower left. Alnitak is the easternmost star in Orion's belt and is seen as the brightest star to the left of the Horsehead. Below Alnitak is the Flame Nebula, with clouds of bright emission and dramatic dark dust lanes. The magnificent emission region, the Orion Nebula (aka M42), lies at the upper right. Immediately to its left is a prominent reflection nebula sometimes called the Running Man. Pervasive tendrils of glowing hydrogen gas are easily traced throughout the region.

Image credit: Roberto Colombari & Federico Pelliccia
A Spectre in the Eastern Veil (2013-10-30)

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 covering 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 reassuring estimated distance of 1,400 light-years from planet Earth. In the composite of image data recorded through narrow band filters, emission from hydrogen atoms in the remnant is shown in red with strong emission from oxygen atoms in blue-green hues. In the western part of the Veil lies another seasonal apparition, the Witch's Broom.

Image credit: Observatorio Zonalunar
Night on a Spooky Planet (2013-10-31)

What spooky planet is this? Planet Earth of course, on the dark and stormy night of September 12 at Hverir, a geothermally active area along the volcanic landscape in northeastern Iceland. Geomagnetic storms produced the auroral display in the starry night sky while ghostly towers of steam and gas venting from fumaroles danced against the eerie greenish light. Tonight, there is still a chance for geomagnetic storms triggered by recent solar activity, so high-latitude skygazers should beware. And ghostly shapes may dance in your neighborhood, too. Have a safe and Happy Halloween!

Image credit: Stéphane
Vetter
NGC 7841: The Smoke Nebula in Frustriaus (2013-11-01)

NGC 7841 is probably known as the Smoke Nebula, found in the modern constellation of Frustriaus, the frustrated astrophotographer. Only a few light-nanoseconds from planet Earth, The Smoke Nebula is not an expanding supernova remnant along the plane of our Milky Way galaxy, though it does look a lot like one. Instead it was created by flash photography of rising smoke. The apparently rich starfield is actually composed of water droplets sprayed from a plant mister by an astrophotographer grown restless during a recent stretch of cloudy weather in Sweden. A single exposure and three external flashes were triggered to capture the not-quite-cosmic snapshot.

Image credit: Göran Strand
Jupiter's Triple Shadow Transit (2013-11-02)

This webcam and telescope image of banded gas giant Jupiter shows the transit of three shadows cast by Jupiter's moons in progress, captured in Belgian skies on October 12 at 0528 UT. Such a three shadow transit is a relatively rare event, even for a large planet with many moons. Visible in the frame are the three Galilean moons responsible, Callisto at the far left edge, Io closest to Jupiter's disk, and Europa below and just left of Io. Of their shadows on the sunlit Jovian cloud tops, Callisto casts the most elongated one near the planet's south polar region at the bottom. Io's shadow is above and right of Jupiter's Great Red Spot. Of course viewed from Jupiter's perspective, these shadow crossings could be seen as solar eclipses, analogous to the Moon's shadow crossing the sunlit face of planet Earth.

Image credit: Leo Aerts
A Rare Hybrid Solar Eclipse (2013-11-03)

A spectacular geocentric celestial event of 2005 was a rare hybrid eclipse of the Sun - a total or an annular eclipse could be seen depending on the observer's location. For Fred Espenak, aboard a gently swaying ship within the middle of the Moon's shadow track about 2,200 kilometers west of the Galapagos, the eclipse was total, the lunar silhouette exactly covering the bright solar disk for a few brief moments. His camera captured a picture of totality revealing the extensive solar corona and prominences rising above the Sun's edge. But for Stephan Heinsius, near the end of the shadow track at Penonome Airfield, Panama, the Moon's apparent size had shrunk enough to create an annular eclipse, showing a complete annulus of the Sun's bright disk as a dramatic ring of fire.  Pictures from the two locations are compared above. How rare is such a hybrid eclipse? Calculations show that during the 21st century just 3.1% (7 out of 224) of solar eclipses are hybrid while hybrids comprise about 5% of all solar eclipses over the period 2000 BC to AD 3000. Today's hybrid solar eclipse is most widely visible beyond the central shadow track as a brief partial eclipse from northeastern Americas through Africa, and along the track in an annular phase for only the first 15 seconds.   Tomorrow's APOD?: Share your best eclipse pictures.

Image credit: Left:
Fred Espenak -
Right:
Stephan Heinsius
Eclipse Over New York (2013-11-04)

A sunrise over New York City rarely looks like this. Yesterday, however, the Sun rose partly eclipsed by the Moon as seen from much of the eastern North American and northern South America.  Simultaneously, much of Africa, already well into daytime, saw the eclipse from beginning to end. The eclipse was unusual in that it was a hybrid -- parts of the Earth saw the Moon as too angularly small to cover the whole Sun, and so at maximum coverage left the Sun surrounded by a ring a fire, while other parts of the Earth saw the Moon as large enough to cover the entire Sun, and so at maximum coverage witnessed a total solar eclipse. Slight changes in the angular size of the Moon as seen from the Earth's surface are caused by the non-flatness of the Earth and the ellipticity of the Moon's orbit.  Pictured above, the famous Empire State Building in New York City is seen to the left of the partially eclipsed Sun, adorned with scenic clouds. The next solar eclipse visible from New York City -- a very slight eclipse -- will occur during the sunset of 2014 October 23.   Growing Gallery: See great eclipse pictures

Image credit: Chris Cook
Kepler-78b: Earth-Sized Planet Discovered (2013-11-05)

ven though Kepler-78b is only slightly larger than the Earth, it should not exist. Its size is extraordinary only in the sense that it is the most similar in size to the Earth of any exoplanet yet directly discovered.  Its orbit, however, is extraordinary in the sense that it circles a Sun-like star 40 times closer than planet Mercury. At such a scathing distance, even rock is liquid.  Models of planet formation predict that no planet can form in such a close orbit, and models of planet evolution predict that Kepler-78b's orbit should decay -- dooming the planet to eventually merge with its parent star. Illustrated above in comparison with the Earth, Kepler-78b was discovered by eclipse with the Earth-trailing Kepler spacecraft and further monitored for subtle wobbles by the HARPS- North, a spectrograph attached to the 3.6-meter Telescopio Nazionale Galileo in the Canary Islands.   New Estimate: 20% of Sun-like stars have a habitable Earth-sized planet.
Creature Aurora Over Norway (2013-11-06)

It was Halloween and the sky looked like a creature. Exactly which creature, the astrophotographer was unsure (but possibly you can suggest one). Exactly what caused the eerie apparition was sure: one of the best auroral displays in recent memory. This spectacular aurora had an unusually high degree of detail. Pictured above, the vivid green and purple  auroral colors are caused by high atmospheric oxygen and nitrogen reacting to a burst of incoming electrons.  Birch trees in Troms�, Norway formed an also eerie foreground. Many other photogenic auroras have been triggered by recent energetic flares on the Sun.   Astrophysicists: Browse 600+ codes in the Astrophysics Source Code Library

Image credit: Ole C. Salomonsen
(Arctic Light Photo)
Eclipse at 44,000 Feet (2013-11-07)

Timing was critical to catch this image of November 3rd's solar eclipse. But flying at 44,000 feet, intrepid eclipse chasers on a chartered jet traveling 500 miles per hour managed to intercept the the Moon's shadow. The remarkable flight made a perpendicular crossing of the central shadow track. Darkening the skies beyond the wing tip at that moment, the Moon's shadow was moving at some 8,000 miles per hour across the Atlantic Ocean, 600 miles southeast of Bermuda. After only an instant of totality, this snapshot captured the lunar disk in silhouette. Rays of sunlight shining past peaks and valleys along the lunar limb created the fleeting appearance of a glistening diamond ring.

Image credit: Ben
Cooper
Solar Eclipse from Uganda (2013-11-08)

The Sun's disk was totally eclipsed for a brief 20 seconds as the Moon's dark umbral shadow raced across Pokwero in northwestern Uganda on November 3rd. So this sharp telescopic view of totality in clear skies from the central African locale was much sought after by eclipse watchers. In the inspiring celestial scene the Moon just covers the overwhelmingly bright photosphere, the lower, normally visible layer of the Sun's atmosphere. Extending beyond the photosphere, the reddish hydrogen alpha glow of the solar chromosphere outlines the lunar silhouette, fading into the Sun's tenuous, hot, outer atmosphere or corona. Planet-sized prominences reaching beyond the limb of the active Sun adorn the edges of the silhouette, including a cloud of glowing plasma separated from the chromosphere near the 1 o'clock position.

Image credit: Jaime Vilinga
Comet Lovejoy with M44 (2013-11-09)

While anxiously waiting for Comet ISON to brighten further as it falls toward the Sun, northern skygazers can also find three other bright comets in the east before dawn. In fact, Comet Lovejoy C/2013 R1 is currently the morning sky's brightest. Only discovered in September and not a sungrazing comet, this Comet Lovejoy is nearing the edge of naked-eye visibility and might be spotted from very dark sky sites. Sporting a greenish coma and tail in this telescopic view taken on November 7, Comet Lovejoy is about 0.5 AU from our fair planet and 1.2 AU from the Sun. The comet is having a photogenic Messier moment, sweeping past well known star cluster M44, the Beehive in Cancer. Yellowish bright star Delta Cancri is near the bottom of the frame.

Image credit: Damian Peach
Comet Between Fireworks and Lightning (2013-11-10)

Sometimes the sky itself is the best show in town.  In January 2007, people from Perth, Australia gathered on a local beach to watch a sky light up with delights near and far.  Nearby, fireworks exploded as part of Australia Day celebrations.  On the far right, lightning from a thunderstorm flashed in the distance.  Near the image center, though, seen through clouds, was the most unusual sight of all: Comet McNaught.  The photogenic comet was so bright that it even remained visible though the din of Earthly flashes.  Comet McNaught has now returned to the outer Solar System and is now only visible with a large telescope. The above image is actually a three photograph panorama digitally processed to reduce red reflections from the exploding firework.    Experience the Universe: Random APOD generator

Image credit: Antti Kemppainen
An Active Sun During a Total Eclipse (2013-11-11)

Sometimes, a total eclipse of the Sun is an opportunity. Taking advantage of such, the above image shows the solar eclipse earlier this month as covered and uncovered by several different solar observatories. The innermost image shows the Sun in ultraviolet light as recorded over a few hours by the SWAP instrument aboard the PROBA2 mission in a sun-synchronous low Earth orbit. This image is surrounded by a ground-based eclipse image, reproduced in blue, taken from Gabon. Further out is a circularly blocked region used to artificially dim the central sun by the LASCO instrument aboard the Sun-orbiting SOHO spacecraft. The outermost image -- showing the outflowing solar corona -- was taken by LASCO ten minutes after the eclipse and shows an outflowing solar corona. Over the past few weeks, our Sun has been showing an unusually high amount of sunspots, CMEs, and flares -- activity that was generally expected as the Sun is currently going through Solar Maximum -- the busiest part of its 11 year solar cycle. The above resultant image is a picturesque montage of many solar layers at once that allows solar astronomers to better match up active areas on or near the Sun's surface with outflowing jets in the Sun's corona.   Free lecture: APOD editor to speak in NYC on Jan. 3

Image credit: D. Seaton (ROB),  
A. Davis & J. M. Pasachoff 
(Williams College Eclipse Expedition),
NRL, 
ESA, 
NASA, NatGeo
The Unexpected Tails of Asteroid P5 (2013-11-12)

What is happening to asteroid P/2013 P5? No one is sure. For reasons unknown, the asteroid is now sporting not one but six discernible tails. The above images were taken two months ago by the orbiting Hubble Space Telescope and show the rapidly changing dust streams. It is not even known when P5 began displaying such unusual tails. Were the main belt asteroid struck by a large meteor, it would be expected to sport a single dust tail. Possible explanations include that light pressure from the Sun is causing the asteroid to rotate increasingly rapidly, which in turn causes pools of previously gravity-bound dust to spin off. Future observations should better indicate how P5 and its dust plumes are evolving and so provide more clues to its nature -- and to how many similar asteroids might exist.
In the Shadow of Saturn (2013-11-13)

In the shadow of Saturn, unexpected wonders appear. The robotic Cassini spacecraft now orbiting Saturn drifted in giant planet's shadow earlier this year and looked back toward the eclipsed Sun.  Cassini saw a unique and celebrated view.  First, the night side of Saturn is seen to be partly lit by light reflected from its own majestic ring system.  Next, Saturn's expansive ring system appears as majestic as always even from this odd angle. Ring particles, many glowing only as irregular crescents, slightly scatter sunlight toward Cassini in this natural color image. Several moons and ring features are also discernible.  Appearing quite prominently is Saturn's E ring, the ring created by the unusual  ice-fountains of the moon Enceladus and the outermost ring visible above.  To the upper left, far in the distance, are the planets Mars and Venus. To the lower right, however, is perhaps the most wondrous spectacle of all: the almost invisible, nearly ignorable,  pale blue dot of Earth.
The Jets of NGC 1097 (2013-11-14)

gmatic spiral galaxy NGC 1097 shines in southern skies, about 45 million light-years away in the chemical constellation Fornax. Its blue spiral arms are mottled with pinkish star forming regions in this colorful galaxy portrait. They seem to have wrapped around a small companion galaxy below and left of center, about 40,000 light-years from the spiral's luminous core. That's not NGC 1097's most peculiar feature, though. The very deep exposure hints of faint, mysterious jets, most easily seen to extend well beyond the bluish arms toward the lower right. In fact, four faint jets are ultimately recognized in optical images of NGC 1097. The jets trace an X centered on the galaxy's nucleus, but probably don't originate there. Instead, they could be fossil star streams, trails left over from the capture and disruption of a much smaller galaxy in the large spiral's ancient past. A Seyfert galaxy, NGC 1097's nucleus also harbors a supermassive black hole.

Image credit: Martin Pugh
The Flash Spectrum of the Sun (2013-11-15)

In a flash, the visible spectrum of the Sun changed from absorption to emission on November 3rd, during the brief total phase of a solar eclipse. That fleeting moment is captured by telephoto lens and diffraction grating in this well-timed image from clearing skies over Gabon in equatorial Africa. With overwhelming light from the Sun's disk blocked by the Moon, the normally dominant absorption spectrum of the solar photosphere is hidden. What remains, spread by the diffraction grating into the spectrum of colors to the right of the eclipsed Sun, are individual eclipse images at each wavelength of light emitted by atoms along the thin arc of the solar chromosphere. The brightest images, or strongest chromospheric emission lines, are due to Hydrogen atoms that produce the red hydrogen alpha emission at the far right and blue hydrogen beta emission to the left. In between, the bright yellow emission image is caused by atoms of Helium, an element only first discovered in the flash spectrum of the Sun.

Image credit: Constantine Emmanouilidi
Active Comet ISON (2013-11-16)

Falling through planet Earth's predawn skies toward its close encounter with the Sun on November 28, Comet ISON is coming to life. The much anticipated comet has now been reported to have substantially increased in activity, surging to naked-eye visibility for dark sites and sprouting a more complex tail. ISON's tail stretches over two degrees in this telephoto skyview from southern Kenya, captured on the morning of November 14. Shown in two panels, the enlarged negative version on the right makes details of the long tail easier to trace, including the tail's separated filaments toward the top of the frame. A sungrazer and first time visitor to the inner solar system, the possibility of ISON's survival to become a bright comet in planet Earth's December skies remains a question.

Image credit: Babak Tafreshi
The Magnificent Tail of Comet McNaught (2013-11-17)

Comet McNaught, the Great Comet of 2007, grew a spectacularly long and filamentary tail.  The magnificent tail spread across the sky and was visible for several days to Southern Hemisphere observers just after sunset.  The amazing tail showed its greatest extent on long-duration, wide-angle camera exposures.  During some times, just the tail itself estimated to attain a peak brightness of  magnitude -5 (minus five), was caught by the comet's discoverer in the above image just after sunset in January 2007 from Siding Spring Observatory in Australia. Comet McNaught, the brightest comet in decades, then  faded as it moved further into southern skies and away from the Sun and Earth. Within the next two weeks of 2013, rapidly brightening Comet ISON might sprout a tail that rivals even Comet McNaught.

Image credit: Robert H. McNaught
Aurora and Unusual Clouds Over Iceland (2013-11-18)

What's happening in the sky? On this cold winter night in Iceland, quite a lot. First, in the foreground, lies the largest glacier in Iceland: Vatnajokull. On the far left, bright green auroras appear to emanate from the glacier as if it was a volcano. Aurora light is reflected by the foreground lake J�kuls�rl�n. On the far right is a long and unusual lenticular cloud tinged with green light emitted from another aurora well behind it. Just above this lenticular cloud are unusual iridescent lenticular clouds displaying a broad spectral range of colors. Far beyond the lenticular is the setting Moon, while far beyond even the Moon are setting stars. The above image was captured in late March of 2012.   Happy Holidays: Free APOD 2014 Calendar in PDF format

Image credit: Stéphane Vetter
(Nuits sacrées)
Globular Cluster M15 from Hubble (2013-11-19)

Stars, like bees, swarm around the center of bright globular cluster M15.  This ball of over 100,000 stars is a relic from the early years of our Galaxy, and continues to orbit the Milky Way's center.  M15, one of about 170 globular clusters remaining, is noted for being easily visible with only binoculars, having at its center one of the densest concentrations of stars known, and containing a high abundance of variable stars and pulsars.  Released only recently, this sharp image taken by the Earth-orbiting Hubble Space Telescope spans about 120 light years. It shows the dramatic increase in density of stars toward the cluster's center.  M15 lies about 35,000 light years away toward the constellation of the Winged Horse (Pegasus).    Gallery: Comets 2013
Heavy Black Hole Jets in 4U1630-47 (2013-11-20)

What are black hole jets made of? Many black holes in stellar systems are surely surrounded by disks of gas and plasma gravitationally pulled from a close binary star companion.  Some of this material, after approaching the black hole, ends up being expelled from the star system in powerful jets emanating from the poles of the spinning black hole. Recent evidence indicates that these jets are composed not only electrons and protons, but also the nuclei of heavy elements such as iron and nickel.  The discovery was made in system 4U1630-47 using CSIRO�s Compact Array of radio telescopes in eastern Australia, and the European Space Agency's Earth-orbiting XMM-Newton satellite.  The 4U1630-47 star system is depicted above in an artist's illustration, with a large blue star on the right and jets emanating from a black hole in the center of the accretion disc on the left. Although the 4U1630-47 star system is thought to contain only a small black hole -- a few times the mass of our Sun -- the implications of the results may be larger: that black holes of larger sizes might also be emitting jets of massive nuclei into the cosmos.   Click Hyperspace: Random APOD Generator