juliensimon/nasa-apod huggingface dataset:
Earth-size Kepler-186f (2014-04-19)

Planet Kepler-186f is the first known Earth-size planet to lie within the habitable zone of a star beyond the Sun. Discovered using data from the prolific planet-hunting Kepler spacecraft, the distant world orbits its parent star, a cool, dim, M dwarf star about half the size and mass of the Sun, some 500 light-years away in the constellation Cygnus. M dwarfs are common, making up about 70 percent of the stars in our Milky Way galaxy. To be within the habitable zone, where surface temperatures allowing liquid water are possible, Kepler-186f orbits close, within 53 million kilometers (about the Mercury-Sun distance) of the M dwarf star, once every 130 days. Four other planets are known in the distant system. All four are only a little larger than Earth and in much closer orbits, also illustrated in the tantalizing artist's vision. While the size and orbit of Kepler-186f are known, its mass and composition are not, and can't be determined by Kepler's transit technique. Still, models suggest that it could be rocky and have an atmosphere, making it potentially the most Earth-like exoplanet discovered so far ...
Ash and Lightning above an Icelandic Volcano (2014-04-20)

Why did a picturesque 2010 volcanic eruption in Iceland create so much ash? Although the large ash plume was not unparalleled in its abundance, its location was particularly noticeable because it drifted across such well-populated areas. The Eyjafjallaj�kull volcano in southern Iceland began erupting on 2010 March 20, with a second eruption starting under the center of a small glacier on 2010 April 14. Neither eruption was unusually powerful.  The second eruption, however, melted a large amount of glacial ice which then cooled and fragmented lava into gritty glass particles that were carried up with the rising volcanic plume.  Pictured above during the second eruption, lightning bolts illuminate ash pouring out of the Eyjafjallaj�kull volcano.

Image credit: Sigur�ur Stefnisson
Massive Nearby Spiral Galaxy NGC 2841 (2014-04-21)

It is one of the more massive galaxies known. A mere 46 million light-years distant, spiral galaxy NGC 2841 can be found in the northern constellation of Ursa Major. This sharp view of the gorgeous island universe shows off a striking yellow nucleus and galactic disk. Dust lanes, small, pink star-forming regions, and young blue star clusters are embedded in the patchy, tightly wound spiral arms. In contrast, many other spirals exhibit grand, sweeping arms with large star-forming regions.  NGC 2841 has a diameter of over 150,000 light-years, even larger than our own Milky Way and captured by this composite image merging exposures from the orbiting 2.4-meter Hubble Space Telescope and the ground-based 8.2-meter Subaru Telescope.  X-ray images suggest that resulting winds and stellar explosions create plumes of hot gas extending into a halo around NGC 2841.

Image credit: Robert Gendler
The El Gordo Massive Galaxy Cluster (2014-04-22)

It is bigger than a bread box. In fact, it is much bigger than all bread boxes put together.  Galaxy cluster ACT-CL J0102-4915 is one of the largest and most massive objects known. Dubbed "El Gordo", the seven billion light years (z = 0.87) distant galaxy cluster spans about seven million light years and holds the mass of a million billion Suns. The above image of El Gordo is a composite of a visible light image from the Hubble Space Telescope, an X-ray image from the Chandra Observatory showing the hot gas in pink, and a computer generated map showing the most probable distribution of dark matter in blue, computed from gravitational lens distortions of background galaxies. Almost all of the bright spots are galaxies. The blue dark matter distribution indicates that the cluster is in the middle stages of a collision between two large galaxy clusters. A careful inspection of the image will reveal a nearly vertical galaxy that appears unusually long.  That galaxy is actually far in the background and has its image stretched by the gravitational lens action of the massive cluster.   Follow APOD on: Facebook,  Google Plus, or Twitter
Arp 81: 100 Million Years Later (2014-04-23)

From planet Earth, we see this strongly distorted pair of galaxies, cataloged as Arp 81, as they were only about 100 million years after their close encounter. The havoc wreaked by their mutual gravitational interaction during the encounter is detailed in this color composite showing twisted streams of gas and dust, a chaos of massive star formation, and a tidal tail stretching for 200 thousand light-years or so as it sweeps behind the cosmic wreckage. Also known as NGC 6622 (left) and NGC 6621, the galaxies are roughly equal in size but are destined to merge into one large galaxy in the distant future, making repeated approaches until they finally coalesce. Located in the constellation Draco, the galaxies are 280 million light-years away. Even more distant background galaxies can be spotted in the sharp, reprocessed, image from Hubble Legacy Archive data.
Lyrids in Southern Skies (2014-04-24)

rth's annual Lyrid meteor shower peaked before dawn on April 22nd, as our fair planet plowed through dust from the tail of long-period comet Thatcher. Even in the dry and dark Atacama desert along Chile's Pacific coast, light from a last quarter Moon made the night sky bright, washing out fainter meteor streaks. But brighter Lyrid meteors still put on a show. Captured in this composited earth-and-sky view recorded during early morning hours, the meteors stream away from the shower's radiant near Vega, alpha star of the constellation Lyra. The radiant effect is due to perspective as the parallel meteor tracks appear to converge in the distance.  Rich starfields and dust clouds of our own Milky Way galaxy stretch across the background.

Image credit: Yuri Beletsky
Hubble's Messier 5 (2014-04-25)

"Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] ..." begins the description of the 5th entry in 18th century astronomer Charles Messier's famous catalog of nebulae and star clusters. Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter. It lies some 25,000 light-years away. Roaming the halo of our galaxy, globular star clusters are ancient members of the Milky Way. M5 is one of the oldest globulars, its stars estimated to be nearly 13 billion years old. The beautiful star cluster is a popular target for Earthbound telescopes. Of course, deployed in low Earth orbit on April 25, 1990, the Hubble Space Telescope has also captured its own stunning close-up view that spans about 20 light-years near the central region of M5. Even close to its dense core at the left, the cluster's aging red and blue giant stars and rejuvenated blue stragglers stand out in yellow and blue hues in the sharp color image.
Southern Annular Eclipse (2014-04-26)

It's eclipse season, and on April 29 around 06:00 UT the shadow of the new Moon will reach out and touch planet Earth, though only just. Still, if you're standing on the continent of Antarctica within a few hundred kilometers of 79 degrees 38.7 minutes South latitude and 131 degrees 15.6 minutes East longitude you could see an annular solar eclipse with the Sun just above the horizon. Because the Moon will be approaching apogee, the most distant point in the elliptical lunar orbit, its apparent size will be too small to completely cover the solar disk. A rare, off-center eclipse, the annular phase will last at most 49 seconds. At its maximum it could look something like this "ring of fire" image from last May's annular solar eclipse, captured by a webcast team operating near Coen, Australia. Otherwise, a partial eclipse with the Moon covering at least some part of the Sun will be seen across a much broader region in the southern hemipshere, including Australia in the afternoon.

Image credit: MWV Observatory
SuitSat-1: A Spacesuit Floats Free (2014-04-27)

A spacesuit floated away from the International Space Station eight years ago, but no investigation was conducted.  Everyone knew that it was pushed by the space station crew.   Dubbed Suitsat-1, the unneeded Russian Orlan spacesuit filled mostly with old clothes was fitted with a faint radio transmitter and released to orbit the Earth. The suit circled the Earth twice before its radio signal became unexpectedly weak. Suitsat-1 continued to orbit every 90 minutes until it burned up in the Earth's atmosphere after a few weeks.  Pictured above, the lifeless spacesuit was photographed in 2006 just as it drifted away from  space station.    Follow APOD on: Facebook,  Google Plus, or Twitter
Time Lapse of a Total Lunar Eclipse (2014-04-28)

Why would a bright full Moon suddenly become dark?  Because it entered the shadow of the Earth. Almost two weeks ago this exact event happened as the Moon underwent a total lunar eclipse. That eclipse, visible from the half of the Earth then facing the Moon, was captured in numerous spectacular photographs and is depicted in the above time lapse video covering about an hour.  The above video, recorded from Mt. Lemmon Sky Center in Arizona, USA, keeps the Earth shadow centered and shows the Moon moving through it from west to east. The temporarily good alignment between Earth, Moon, and Sun will show itself again tomorrow -- precisely half a moon-th (month) later -- when part of the Earth will pass through part of the new Moon's shadow.   APOD Collection: Pleiades Star Cluster (highlighted recently on Cosmos)
Aurora Dog over Alaska (2014-04-29)

Sometimes it is hard to believe what you see in the sky. While leading his annual aurora tour last month near Fairbanks in central Alaska, astrophotographer John Chumack and his company saw a most unusual aurora. This bright aurora appeared to change into the shape of a jumping dog, complete with a curly tail. He was able to capture the fleeting natural apparition in the above image with a 15-second exposure through a wide-angle lens. By coincidence, he also captured a background sky filled with familiar highlights. Planets visible include bright Jupiter through the dog's front legs and reddish Mars below the dog's hind legs. Stars visible include the Big Dipper stars above the dog's midsection and reddish Betelgeuse shining on the far right. This dog would not be following him home, however, and within a few minutes morphed into other shapes before the geomagnetic storm particles that created it shifted to strike the Earth elsewhere.

Image credit: John Chumack
A Partially Eclipsed Setting Sun (2014-04-30)

If you look closely, you will see something quite unusual about this setting Sun. There are birds flying to the Sun's left, but that's not so unusual. A dark sea covers the Sun's bottom, and dark clouds cover parts of the middle, but they are also not very unusual. More unusual is the occulted piece at the top right. And that's no occulting cloud -- that's the Moon. Yesterday the Moon moved in front of part of the Sun as visible from Australia, and although many locations reported annoying clouds, a partially eclipsed Sun would occasionally peek through as it set. The above image was captured yesterday on the western horizon of Adelaide, South Australia. The maximum eclipse was visible only from a small part of Antarctica where the entire Moon could be seen covering the entire center of the Sun in what is known as an annular eclipse, leaving only a ring of fire from the Sun peeking out around the edges. The next solar eclipse will be another partial eclipse, will occur on 2014 October 23, and will be visible from most of North America near sunset.   Gallery: Yesterday's Solar Eclipse

Image credit: Andrew Wall
Brisbane Sunset Moonset (2014-05-01)

In skies over Brisbane at the southeastern corner of Queensland, Australia, Planet Earth, the Sun and New Moon set together on April 29. There the celestial line-up, the first solar eclipse of 2014, was seen as a partial solar eclipse. This dramatic composite is a digital stack of images taken about 5 minutes apart with telephoto lens and solar filter. It follows the eclipse in progress, approaching a western horizon where crepuscular rays from cloud banks in silhouette joined the silhouetted Moon. From Brisbane, the maximum eclipse phase with the Moon covering about 25% of the Sun occurred just after sunset. Only from a remote spot on the continent of Antarctica was it even possible to see the eclipse in its brief annular phase, the entire dark lunar disk surrounded by a thin, bright ring of fire.

Image credit: Stephen Mudge
That Night over Half Dome (2014-05-02)

Captured one night last May this eight frame mosaic starts on the left, down Northside Drive through Yosemite National Park. It ends thousands of light-years away though, as the arc of the Milky Way tracks toward the center of our galaxy on the right, far beyond the park's rugged skyline. That night was still moonless when the storm clouds retreated, so the rocky faces of the surrounding mountains are lit by campfires and artificial lights. Yosemite Falls is at the left. The granite face of Half Dome juts above the far horizon, near the center of the view. The remarkable flash above it is a bright meteor. Part of the annual Eta Aquarid meteor shower the colorful streak is moving up, its trail pointing directly back to the shower's radiant, low in Aquarius. This year's Eta Aquarids should peak in the moonless early morning hours of May 6 as the Earth sweeps through dust from the tail of Comet Halley.

Image credit: Rogelio Bernal
Andreo
T Tauri and Hind's Variable Nebula (2014-05-03)

The yellowish star near center in this dusty telescopic skyview is T Tauri, prototype of the class of T Tauri variable stars. Just next door is the yellow cosmic cloud historically known as Hind's Variable Nebula (NGC 1555). Over 400 light-years away, at the edge of an otherwise invisible molecular cloud, both star and nebula are seen to vary significantly in brightness but not necessarily at the same time, adding to the mystery of the intriguing region. T Tauri stars are now generally recognized as young (less than a few million years old), sun-like stars still in the early stages of formation. To further complicate the picture, infrared observations indicate that T Tauri itself is part of a multiple system and suggest that the associated Hind's Nebula may also contain a very young stellar object. The naturally colored image spans about 7 light-years at the estimated distance of T Tauri.

Image credit: Bill
Snyder
A Scorpius Sky Spectacular (2014-05-04)

If Scorpius looked this good to the unaided eye, humans might remember it better.  Scorpius more typically appears as a few bright stars in a well-known but rarely pointed out zodiacal constellation. To get a spectacular image like this, though, one needs a good camera, color filters, and a digital image processor.  To bring out detail, the above image not only involved long duration exposures taken in several colors, but one exposure in a very specific red color emitted by hydrogen.  The resulting image shows many breathtaking features.  Vertically across the image left is part of the plane of our Milky Way Galaxy.   Visible there are vast clouds of bright stars and long filaments of dark dust.  Jutting out diagonally from the Milky Way in the image center are dark dust bands known as the Dark River.  This river connects to several bright stars on the right that are part of Scorpius' head and claws, and include the bright star Antares.  Above and right of Antares is an even brighter planet Jupiter. Numerous red emission nebulas and blue reflection nebulas are visible throughout the image. Scorpius appears prominently in southern skies after sunset during the middle of the year.   Astrophysicists: Preview changes coming to the Astrophysics Source Code Library

Image credit: St�phane Guisard, 
TWAN
Galaxy Cluster Magnifies Distant Supernova (2014-05-05)

How do you calibrate a huge gravitational lens? In this case the lens is the galaxy cluster Abell 383, a massive conglomeration of galaxies, hot gas, and dark matter that lies about 2.5 billion light years away (redshift z=0.187). What needs calibrating is the mass of the cluster, in particular the amount and distribution of dark matter. A new calibration technique has been tested recently that consists of waiting for supernovas of a very specific type to occur behind a galaxy cluster, and then figuring out how much the cluster must have magnified these supernovas through gravitational lensing.  This technique complements other measures including computing the dark matter needed to contain internal galaxy motions, to confine cluster hot gas, and to create the gravitational lens image distortions.  Pictured above from the Hubble Space Telescope, galaxy cluster A383 shows its gravitational lens capabilities on the right by highly distorting background galaxies behind the cluster center. On the left is a distant galaxy shown both before and after a recent revealing supernova. To date, calibration-quality supernovas of Type Ia have been found behind two other galaxy clusters by the Cluster Lensing And Supernova survey with Hubble (CLASH) project.    Follow APOD on: Facebook,  Google Plus, or Twitter
Orange Sun Sparking (2014-05-06)

Our Sun has become quite a busy place.  Taken only two weeks ago, the Sun was captured sporting numerous tumultuous regions including active sunspot regions AR 2036 near the image top and AR 2038 near the center.  Only four years ago the Sun was emerging from an unusually quiet Solar Minimum that had lasted for years. The above image was recorded in a single color of light called Hydrogen Alpha, inverted, and false colored. Spicules cover much of the Sun's face like a carpet. The gradual brightening towards the Sun's edges is caused by increased absorption of relatively cool solar gas and called limb darkening.  Just over the Sun's edges, several filamentary prominences protrude, while prominences on the Sun's face are seen as light streaks.  Possibly the most visually interesting of all are the magnetically tangled active regions containing relatively cool sunspots, seen as white dots.  Currently at Solar Maximum -- the most active phase in its 11-year magnetic cycle, the Sun's twisted magnetic field is creating numerous solar "sparks" which include eruptive solar prominences, coronal mass ejections, and flares which emit clouds of particles that may impact the Earth and cause auroras. One flare two years ago released such a torrent of charged particles into the Solar System that it might have disrupted satellites and compromised power grids had it struck planet Earth.   News: Free APOD Lecture in Paris on June 17

Image credit: Alan Friedman
(Averted Imagination)
Curiosity Inspects Mt. Remarkable on Mars (2014-05-07)

What has the Curiosity rover come across on Mars? Dubbed Mount Remarkable, the rolling robot has chanced upon this notable 5-meter tall mound during its continuing journey around and, eventually, up 5.5-kilometer high Mt. Sharp. Unsure of the density of the surrounding layered sandstone, the human team on Earth has instructed the car-sized rover on Mars to drill into a rock on the side of Mt. Remarkable to investigate. Quite possibly, water involved in creating the dense sandstone could have helped to support ancient life on the red planet.  Mt. Sharp, the unusual central peak of Gale Crater, has a similar base-to-peak height as Earth's Mt. Everest.
The Tail of the Hamburger Galaxy (2014-05-08)

Sharp telescopic views of NGC 3628 show a puffy galactic disk divided by dark dust lanes. Of course, this deep portrait of the magnificent, edge-on spiral galaxy puts some astronomers in mind of its popular moniker, the Hamburger Galaxy. It also reveals a small galaxy nearby, likely a satellite of NGC 3628, and a faint but extensive tidal tail. The tantalizing island universe itself is about 100,000 light-years across and 35 million light-years away in the northern springtime constellation Leo. Its drawn out tail stretches for about 300,000 light-years, even beyond the left edge of the wide frame. NGC 3628 shares its neighborhood in the local Universe with two other large spirals M65 and M66 in a grouping otherwise known as the Leo Triplet. Gravitational interactions with its cosmic neighbors are likely responsible for creating the tidal tail, as well as the extended flare and warp of this spiral's disk.

Image credit: Martin Pugh
Halley Dust and Milky Way (2014-05-09)

The early morning hours of May 6 were moonless when grains of cosmic dust streaked through dark skies. Swept up as planet Earth plows through dusty debris streams left behind periodic Comet Halley, the annual meteor shower is known as the Eta Aquarids. This inspired exposure captures a meteor streak moving left to right through the frame. Its trail points back across the arc of the Milky Way to the shower's radiant above the local horizon in the constellation Aquarius. Known for speed Eta Aquarid meteors move fast, entering the atmosphere at about 66 kilometers per second. Still waters of the small pond near Albion, Maine, USA reflect the starry scene and the orange glow of nearby artificial lights scattered by a low cloud bank. Of course, northern hemisphere skygazers are expecting a new meteor shower on May 24, the Camelopardalids, caused by dust from periodic comet 209P/LINEAR.

Image credit: Mike Taylor
Inside the Flame Nebula (2014-05-10)

The Flame Nebula stands out in this optical image of the dusty, crowded star forming regions toward Orion's belt, a mere 1,400 light-years away. X-ray data from the Chandra Observatory and infrared images from the Spitzer Space Telescope can take you inside the glowing gas and obscuring dust clouds though. Swiping your cursor (or clicking the image) will reveal many stars of the recently formed, embedded cluster NGC 2024, ranging in age from 200,000 years to 1.5 million years young. The X-ray/infrared composite image overlay spans about 15 light-years across the Flame's center. The X-ray/infrared data also indicate that the youngest stars are concentrated near the middle of the Flame Nebula cluster. That's the opposite of the simplest models of star formation for the stellar nursery that predict star formation begins in the denser center of a molecular cloud core. The result requires a more complex model; perhaps star formation continues longer in the center, or older stars are ejected from the center due to subcluster mergers.
Valles Marineris: The Grand Canyon of Mars (2014-05-11)

The largest canyon in the Solar System cuts a wide swath across the face of Mars.  Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep.  By comparison, the Earth's Grand Canyon in Arizona, USA is 800 kilometers long, 30 kilometers across, and 1.8 kilometers deep.  The origin of the Valles Marineris remains unknown, although a leading hypothesis holds that it started as a crack billions of years ago as the planet cooled.  Several geologic processes have been identified in the canyon.  The above mosaic was  created from over 100 images of Mars taken by Viking Orbiters in the 1970s.    Click Hyperspace: Random APOD Generator