juliensimon/nasa-apod huggingface dataset:
Facing NGC 6946 (2018-02-24)

From our vantage point in the Milky Way Galaxy, we see NGC 6946 face-on. The big, beautiful spiral galaxy is located just 20 million light-years away, behind a veil of foreground dust and stars in the high and far-off constellation of Cepheus. From the core outward, the galaxy's colors change from the yellowish light of old stars in the center to young blue star clusters and reddish star forming regions along the loose, fragmented spiral arms. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, since the early 20th century ten confirmed supernovae, the death explosions of massive stars, were discovered in NGC 6946. Nearly 40,000 light-years across, NGC 6946 is also known as the Fireworks Galaxy. This remarkable portrait of NGC 6946 is a composite that includes image data from the 8.2 meter Subaru Telescope on Mauna Kea.
AE Aurigae and the Flaming Star Nebula (2018-02-25)

Why is AE Aurigae called the flaming star? For one reason, the surrounding nebula IC 405 is named the Flaming Star Nebula because the region seems to harbor smoke, even though nothing is on fire, including interior star AE Aurigae.  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. 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 is visible near the nebula center and is so hot it is blue, emitting light so energetic it knocks electrons away from atoms in the surrounding gas. When an atom recaptures an electron, light is emitted creating the surrounding emission nebula. 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).

Image credit: Martin Pugh
Passing Jupiter (2018-02-26)

Here comes Jupiter! NASA's robotic spacecraft Juno is continuing on its 53-day, highly-elongated orbits around our Solar System's largest planet.  The featured video is from perijove 11, the eleventh time Juno has passed near Jupiter since it arrived in mid-2016.  This time-lapse, color-enhanced movie covers about four hours and morphs between 36 JunoCam images. The video begins with Jupiter rising as Juno approaches from the north. As Juno reaches its closest view -- from about 3,500 kilometers over Jupiter's cloud tops -- the spacecraft captures the great planet in tremendous detail. Juno passes light zones and dark belt of clouds that circle the planet, as well as numerous swirling circular storms, many of which are larger than hurricanes on Earth.  After the perijove, Jupiter recedes into the distance, now displaying the unusual clouds that appear over Jupiter's south.  To get desired science data, Juno swoops so close to Jupiter that its instruments are exposed to very high levels of radiation.
Dueling Bands in the Night (2018-02-27)

What are these two bands in the sky? The more commonly seen band is the one on the right and is the central band of our Milky Way galaxy. Our Sun orbits in the disk of this spiral galaxy, so that from inside, this disk appears as a band of comparable brightness all the way around the sky. The Milky Way band can also be seen all year -- if out away from city lights.  The less commonly seem band, on the left, is zodiacal light -- sunlight reflected from dust orbiting the Sun in our Solar System.  Zodiacal light is brightest near the Sun and so is best seen just before sunrise or just after sunset.  On some evenings in the north, particularly during the months of March and April, this ribbon of zodiacal light can appear quite prominent after sunset.  It has recently been determined that zodiacal dust was mostly expelled by comets that have passed near Jupiter.  Only on certain times of the year will the two bands be seen side by side, in parts of the sky, like this.  Here the two streaks of light appear like the continuation of the banks of the Liver River into the sky. The featured panorama of consecutive exposures was recorded about three weeks ago in North Jutland,  Denmark.
NGC 613 in Dust, Stars, and a Supernova (2018-02-28)

Where did that spot come from?  Amateur astronomer Victor Buso was testing out a new camera on his telescope in 2016 when he noticed a curious spot of light appear -- and remain. After reporting this unusual observation, this spot was determined to be light from a supernova just as it was becoming visible -- in an earlier stage than had ever been photographed optically before. The discovery before and after images, taken about an hour apart, are shown in the inset of a more detailed image of the same spiral galaxy, NGC 613, taken by the Hubble Space Telescope. Follow-up observations show that SN 2016gkg was likely the explosion of a supergiant star, and Buso likely captured the stage where the outgoing detonation wave from the stellar core broke through the star's surface.  Since astronomers have spent years monitoring galaxies for supernovas without seeing such a "break out" event, the odds of Buso capturing this have been compared to winning a lottery.
The Lunar X (V) (2018-03-01)

The striking X in this lunarscape is easily visible in binoculars or a small telescope, but not too many have seen it. The catch is, this lunar X is fleeting and only apparent in the hours before the Moon's first quarter phase. Along the shadow line between lunar day and night, the X illusion is produced by a configuration of craters seen here toward the left, Blanchinus, La Caille and Purbach. Near the Moon's first quarter phase, an astronaut standing close to the craters' position would see the slowly rising Sun very near the horizon. Temporarily, crater walls would be in sunlight while crater floors would still be in darkness. Seen from planet Earth, contrasting sections of bright walls against the dark floors by chance look remarkably like an X. This sharp image of the Lunar X was captured on February 22nd. For extra credit, sweep your gaze along the lunar terminator and you can also spot the Lunar V.

Image credit: Henrik Adamsson
Alborz Mountain Star Trails (2018-03-02)

Colourful star trails arc through the night in this wide-angle mountain and skyscape. From a rotating planet, the digitally added consecutive exposures were made with a camera fixed to a tripod and looking south, over northern Iran's Alborz Mountain range. The stars trace concentric arcs around the planet's south celestial pole, below the scene's rugged horizon. Combined, the many short exposures also bring out the pretty star colours. Bluish trails are from stars hotter than our Sun, while yellowish trails are from cooler stars. Near the center, the remarkably pinkish trail was traced by the star-forming Orion Nebula.

Image credit: Stéphane Guisard
Southwest Mare Fecunditatis (2018-03-03)

Frank Borman, James Lovell, and William Anders journeyed from Earth to the Moon and back again in December of 1968. From lunar orbit, their view of craters in southwest Mare Fecunditatis is featured in this stereo anaglyph, best experienced from armchairs on planet Earth with red/blue glasses. Goclenius is the large impact crater in the foreground. About 70 kilometers (45 miles) in diameter its lava-flooded floor is scarred by rilles or grooves, long, narrow depressions in the surface. Crossing the crater walls and central peaks the rilles were likely formed after the crater itself. In the background, the two large craters with smooth floors are Colombo A (top) and Magelhaens. Magelhaens A, the background crater with the irregular floor, is about 35 kilometers (20 miles) in diameter.
Clouds, Birds, Moon, Venus (2018-03-04)

Sometimes the sky above can become quite a show. In early September of 2010, for example, the Moon and Venus converged, creating quite a sight by itself for sky enthusiasts around the globe.  From some locations, though, the sky was even more picturesque. In the featured image taken in Spain, a crescent Moon and the planet Venus, on the far right, were captured during sunset posing against a deep blue sky.  In the foreground, dark storm clouds loom across the image bottom, while a white anvil cloud shape appears above. Black specks dot the frame, caused by a flock of birds taking flight. Very soon after this picture was taken, however, the birds passed by, the storm ended, and Venus and the Moon set.  Bright Venus is again visible just after sunset this month (2018 March) and will appear quite near Mercury tonight and the rest of this week.

Image credit: Isaac Guti�rrez Pascual
The Hubble Ultra-Deep Field in Light and Sound (2018-03-05)

Have you heard about the Hubble Ultra-Deep Field?  Either way, you've likely not heard about it like this -- please run your pointer over the featured image and listen!  The Hubble Ultra-Deep Field (HUDF) was created in 2003-2004 with the Hubble Space Telescope staring for a long time toward near-empty space so that distant, faint galaxies would become visible.  One of the most famous images in astronomy, the HUDF is featured here in a vibrant way -- with sonified distances. Pointing to a galaxy will play a note that indicates its approximate redshift. Because redshifts shift light toward the red end of the spectrum of light, they are depicted here by a shift of tone toward the low end of the spectrum of sound.  The further the galaxy, the greater its cosmological redshift (even if it appears blue), and the lower the tone that will be played. The average galaxy in the HUDF is about 10.6 billion light years away and sounds like an F#. What's the most distant galaxy you can find?  This Astronomy Picture of the Day (APOD) is based on an entry of new site called Astronomy Sound of the Month (AstroSoM).    Note: The sounds will only play on some browsers.
Colorful Airglow Bands Surround Milky Way (2018-03-06)

Why would the sky glow like a giant repeating rainbow?  Airglow.  Now air glows all of the time, but it is usually hard to see. A disturbance however -- like an approaching storm -- may cause noticeable rippling in the Earth's atmosphere. These gravity waves are oscillations in air analogous to those created when a rock is thrown in calm water.  Red airglow likely originates from OH molecules about 87-kilometers high, excited by ultraviolet light from the Sun, while orange and green airglow is likely caused by sodium and oxygen atoms slightly higher up.  While driving near Keluke Lake in Qinghai Provence in China, the photographer originally noticed mainly the impressive central band of the Milky Way Galaxy.  Stopping to photograph it, surprisingly, the resulting sensitive camera image showed airglow bands to be quite prominent and span the entire sky. The featured image has been digitally enhanced to make the colors more vibrant.    Follow APOD on: Facebook,  Google Plus,  Instagram, or Twitter

Image credit: Xiaohan Wang
Arcs, Jets, and Shocks near NGC 1999 (2018-03-07)

This tantalizing array of nebulas and stars can be found about two degrees south of the famous star-forming Orion Nebula. The region abounds with energetic young stars producing jets and outflows that push through the surrounding material at speeds of hundreds of kilometers per second. The interaction creates luminous shock waves known as Herbig-Haro (HH) objects. For example, the graceful, flowing arc just right of center is cataloged as HH 222, also called the Waterfall Nebula. Seen below the Waterfall, HH 401 has a distinctive cone shape. The bright bluish nebula below and left of center is NGC 1999, a dusty cloud reflecting light from an embedded variable star. The entire cosmic vista spans over 30 light-years, near the edge of the Orion Molecular Cloud Complex some 1,500 light-years distant.   Open Science: Browse 1,600+ codes in the Astrophysics Source Code Library

Image credit: Mark Hanson;
 Annotation:  Sakib Rasool 
(StarSurfin)
Cyclones at Jupiter's North Pole (2018-03-08)

Juno's Jovian Infrared Auroral Mapper data was used to construct this stunning view of cyclones at Jupiter's North Pole. Measuring the thermal emission from Jovian cloud tops, the infrared observations are not restricted to the hemisphere illuminated by sunlight. They reveal eight cyclonic features that surround a cyclone about 4,000 kilometers in diameter, just offset from the giant planet's geographic North Pole. Similar data show a cyclone at the Jovian South Pole with five circumpolar cyclones. The South Pole cyclones are slightly larger than their northern cousins. Cassini data has shown that gas giant Saturn's north and south poles each have a single cyclonic storm system.
Horsehead: A Wider View (2018-03-09)

Combined image data from the massive, ground-based VISTA telescope and the Hubble Space Telescope was used to create this wide perspective of the interstellar landscape surrounding the famous Horsehead Nebula. Captured at near-infrared wavelengths, the region's dusty molecular cloud sprawls across the scene that covers an angle about two-thirds the size of the Full Moon on the sky. Left to right the frame spans just over 10 light-years at the Horsehead's estimated distance of 1,600 light-years. Also known as Barnard 33, the still recognizable Horsehead Nebula stands at the upper right, the near-infrared glow of a dusty pillar topped with newborn stars. Below and left, the bright reflection nebula NGC 2023 is itself the illuminated environs of a hot young star. Obscuring clouds below the base of the Horsehead and on the outskirts of NGC 2023 show the tell-tale far red emission of energetic jets, known as Herbig-Haro objects, also associated with newborn stars.
Phases of the Moon (2018-03-10)

Look at the Moon every night and its visible sunlit portion gradually changes. In phases progressing from New Moon to Full Moon to New Moon again, a lunar cycle or lunation is completed in about 29.5 days. Top left to bottom right, these frames show the range of lunar phases for 25 consecutive nights beginning on January 18, following an almost complete lunation. They skip the 2 days just after and 2 days before New Moon, when the lunar phase is at best a narrow crescent, close to the Sun and really hard to see. Of course, mostly clear Arizona night skies and a little help from a friend were required to complete this lunar cycle project, imaging in early evening for the first half and late evening and early morning for the second half of the lunation. For extra credit, the cycle was centered on the Full Moon of January 31. That was the second Full Moon in January, when the Moon was near lunar orbit perigee and took on reddish hues during a total lunar eclipse.

Image credit: Jean-Francois Gout
Dual Particle Beams in Herbig-Haro 24 (2018-03-11)

This might look like a double-bladed lightsaber, but these two cosmic jets actually beam outward from a newborn star in a galaxy near you. Constructed from Hubble Space Telescope image data, the stunning scene spans about half a light-year across Herbig-Haro 24 (HH 24), some 1,300 light-years away in the stellar nurseries of the Orion B molecular cloud complex. Hidden from direct view, HH 24's central protostar is surrounded by cold dust and gas flattened into a rotating accretion disk. As material from the disk falls toward the young stellar object it heats up. Opposing jets are blasted out along the system's rotation axis. Cutting through the region's interstellar matter, the narrow, energetic jets produce a series of glowing shock fronts along their path.
Flying over the Earth at Night II (2018-03-12)

What would it be like to orbit the Earth? The International Space Station (ISS) does this every 90 minutes, and sometimes the astronauts on board take image sequences that are made into videos. The featured time-lapse video shows many visual spectacles of the dark Earth below. First, as the video begins, green and red auroras are visible on the upper left above white clouds.  Soon city lights come into view, and it becomes clear you are flying over North America, eventually passing over Florida. In the second sequence you fly over Europe and Africa, eventually passing over the Nile River.  Brief flashes of light are lightning in storms. Stars far in the distance can be seen rising through the greenish-gold glow of the Earth's atmosphere.
The Complete Galactic Plane: Up and Down (2018-03-13)

Is it possible to capture the entire plane of our galaxy in a single image? Yes, but not in one exposure -- and it took some planning to do it in two. The top part of the featured image is the night sky above Lebanon, north of the equator, taken in 2017 June. The image was taken at a time when the central band of the Milky Way Galaxy passed directly overhead. The bottom half was similarly captured six months later in latitude-opposite Chile, south of Earth's equator. Each image therefore captured the night sky in exactly the opposite direction of the other, when fully half the Galactic plane was visible. The southern half was then inverted -- car and all -- and digitally appended to the top half to show the entire central band of our Galaxy, as a circle, in a single image.  Many stars and nebulas are visible, with the Large Magellanic Cloud being particularly notable inside the lower half of the complete galactic circle.

Image credit: Moophz Himself
(Maroun Habib)
Night Sky Highlights: March to May (2018-03-14)

What might you see in the night sky over the next few months? The featured graphic gives a few highlights. Viewed as a clock face centered at the bottom, sky events in March fan out toward the left, April toward the top, and May toward the right.  Objects relatively close to Earth are illustrated, in general, as nearer to the cartoon figure with the telescope at the bottom center -- although almost everything pictured can be seen without a telescope.  Sky highlights this season include a bright Venus in the evening sky during March, the Lyrids meteor shower during April, and Jupiter entering the evening sky during May.  As true in every season, the International Space Station (ISS) can be sometimes be found drifting across your sky if you know just when and where to look.    News: Stephen Hawking Dies at 76

Image credit: Universe2go.com
Catalog Entry Number 1 (2018-03-15)

very journey has a first step and every catalog a first entry. First entries in six well-known deep sky catalogs appear in these panels, from upper left to lower right in chronological order of original catalog publication. From 1774, Charles Messier's catalog entry number 1 is M1, famous cosmic crustacean and supernova remnant the Crab Nebula. J.L.E. Dreyer's (not so new) New General Catalog was published in 1888. A spiral galaxy in Pegasus, his NGC 1 is centered in the next panel. Just below it in the frame is another spiral galaxy cataloged as NGC 2. In Dreyer's follow-on Index Catalog (next panel), IC 1 is actually a faint double star, though. Now recognized as part of the Perseus molecular cloud complex, dark nebula Barnard 1 begins the bottom row from Dark Markings of the Sky, a 1919 catalog by E.E. Barnard. Abell 1 is a distant galaxy cluster in Pegasus, from George Abell's 1958 catalog of Rich Clusters of Galaxies. The final panel is centered on vdB 1, from Sidney van den Bergh's 1966 study. The pretty, blue galactic reflection nebula is found in the constellation Cassiopeia.

Image credit: Bernhard Hubl
The Seagull and the Duck (2018-03-16)

Seen as a seagull and a duck, these nebulae are not the only cosmic clouds to evoke images of flight. But both are winging their way across this broad celestial landscape, spanning almost 7 degrees across planet Earth's night sky toward the constellation Canis Major. The expansive Seagull (top center) is itself composed of two major cataloged emission nebulae. Brighter NGC 2327 forms the head with the more diffuse IC 2177 as the wings and body. Impressively, the Seagull's wingspan would correspond to about 250 light-years at the nebula's estimated distance of 3,800 light-years. At the lower right, the Duck appears much more compact and would span only about 50 light-years given its 15,000 light-year distance estimate. Blown by energetic winds from an extremely massive, hot star near its center, the Duck nebula is cataloged as NGC 2359. Of course, the Duck's thick body and winged appendages also lend it the slightly more dramatic popular moniker, Thor's Helmet.

Image credit: Raul
Villaverde Fraile
The Crab from Space (2018-03-17)

The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from the death explosion of a massive star. This intriguing false-color image combines data from space-based observatories, Chandra, Hubble, and Spitzer, to explore the debris cloud in X-rays (blue-white), optical (purple), and infrared (pink) light. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.
Rotating Moon from LRO (2018-03-18)

No one, presently, sees the Moon rotate like this. That's because the Earth's moon is tidally locked to the Earth, showing us only one side.  Given modern digital technology, however, combined with many detailed images returned by the Lunar Reconnaissance Orbiter (LRO), a high resolution virtual Moon rotation movie has been composed. The above time-lapse video starts with the standard Earth view of the Moon. Quickly, though, Mare Orientale, a large crater with a dark center that is difficult to see from the Earth, rotates into view just below the equator.  From an entire lunar month condensed into 24 seconds, the video clearly shows that the Earth side of the Moon contains an abundance of dark lunar maria, while the lunar far side is dominated by bright lunar highlands. Currently, over 20 new missions to the Moon are under active development from four different countries, most of which have expected launch dates either this year or next.
The Nebra Sky Disk (2018-03-19)

Some consider it the oldest known illustration of the night sky. But what, exactly, does it depict, and why was it made? The Nebra sky disk was found with a metal detector in 1999 by treasure hunters near Nebra, Germany, in the midst of several bronze-age weapons.  The ancient artifact spans about 30 centimeters and has been associated with the Unetice culture that inhabited part of Europe around 1600 BC. Reconstructed, the dots are thought to represent stars, with the cluster representing the Pleiades, and the large circle and the crescent representing the Sun and Moon. The purpose of the disk remains unknown -- hypotheses including an astronomical clock, a work of art, and a religious symbol. Valued at about $11 million, some believe that the Nebra sky disk is only one of a pair, with the other disk still out there waiting to be discovered.
Chicagohenge: Equinox in an Aligned City (2018-03-20)

Sometimes, in a way, Chicago is like a modern Stonehenge. The way is east to west, and the time is today.  Today, and every equinox, the Sun will set exactly to the west, everywhere on Earth. Therefore, today in Chicago, the Sun will set directly down the long equatorially-aligned grid of streets and buildings, an event dubbed #chicagohenge.  Featured here is a Chicago Henge picture taken during the last equinox in mid-September of 2017 looking along part of Upper Wacker Drive.  Many cities, though, have streets or other features that are well-aligned to Earth's spin axis. Therefore, quite possibly, your  favorite street may also run east - west. Tonight at sunset, with a quick glance, you can actually find out.

Image credit: Anthony Artese