juliensimon/nasa-apod huggingface dataset:
Two Views of Earth (2013-07-23)

In a cross-Solar System interplanetary first, our Earth was photographed during the same day from both Mercury and Saturn. Pictured on the left, Earth is the pale blue dot just below the rings of Saturn, as captured by the robotic Cassini spacecraft now orbiting the gas giant. Pictured on the right, the Earth-Moon system is seen against a dark background, as captured by the robotic MESSENGER spacecraft now orbiting Mercury. In the MESSENGER image, the Earth (left) and Moon (right) shine brightly with reflected sunlight. MESSENGER took the overexposed image last Friday as part of a search for small natural satellites of the innermost planet, moons that would be expected to be quite dim. During this same day, humans across planet Earth snapped many of their own pictures of Saturn.
A Year of Sky on Earth (2013-07-24)

ch panel shows one day. With 360 movie panels, the sky over (almost) an entire year is shown in time lapse format as recorded by a video camera on the roof of the Exploratorium museum in San Francisco, California. The camera recorded an image every 10 seconds from before sunrise to after sunset and from mid-2009 to mid-2010.  A time stamp showing the local time of day is provided on the lower right. The videos are arranged chronologically, with July 28 shown on the upper left, and January 1 located about about half way down.  Although every day lasts 24 hours, daylight lasts longest in the northern hemisphere in June and the surrounding summer months, a fact which can be seen here as the bottom (and soon top) videos are the first to light up with dawn. The initial darkness in the middle depicts the delayed dawn and fewer daylight hours of winter. In the videos, darkness indicates night, blue depicts clear day, while gray portrays pervasive daytime cloud cover. Many videos show complex patterns of clouds moving across the camera's wide field as that day progresses. As the videos collectively end, sunset and then darkness descend first on the winter days just above the middle, and last on the mid-summer near the bottom.

Image credit: Ken Murphy  
(MurphLab);
 Music  Ariel (Moby)
The Beautiful Trifid (2013-07-25)

The beautiful Trifid Nebula is a cosmic study in contrasts. Also known as M20, it lies about 5,000 light-years away toward the nebula rich constellation Sagittarius. A star forming region in the plane of our galaxy, the Trifid illustrates three different types of astronomical nebulae; red emission nebulae dominated by light emitted by hydrogen atoms, blue reflection nebulae produced by dust reflecting starlight, and dark nebulae where dense dust clouds appear in silhouette. The bright red emission region, roughly separated into three parts by obscuring dust lanes, lends the Trifid its popular name. But in this sharp, colorful scene, the red emission is also surrounded by the the telltale blue haze of reflection nebulae. Pillars and jets sculpted by newborn stars, below and left of the emission nebula's center, appear in Hubble Space Telescope close-up images of the region. The Trifid Nebula is about 40 light-years across.

Image credit: Máximo Ruiz
The Elephant's Trunk in IC 1396 (2013-07-26)

Like an illustration in a galactic Just So Story, the Elephant's Trunk Nebula winds through the emission nebula and young star cluster complex IC 1396, in the high and far off constellation of Cepheus. Of course, the cosmic elephant's trunk is over 20 light-years long. This composite was recorded through narrow band filters that transmit the light from ionized hydrogen, sulfur, and oxygen atoms in the region. The resulting image highlights the bright swept-back ridges that outline pockets of cool interstellar dust and gas. Such embedded, dark, tendril-shaped clouds contain the raw material for star formation and hide protostars within the obscuring cosmic dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a large region on the sky, spanning over 5 degrees. This close-up mosaic covers a 2 degree wide field, about the size of 4 Full Moons.

Image credit: Juan Lozano de Haro
Atacama's Cloudy Night (2013-07-27)

Storm clouds do sometimes come to Chile's Atacama desert, known as the driest place on Earth. These washed through the night sky just last month during the winter season, captured in this panoramic view. Drifting between are cosmic clouds more welcome by the region's astronomical residents though, including dark dust clouds in silhouette against the crowded starfields and nebulae of the central Milky Way. Below and right of center lies the Large Magellanic Cloud, appropriately named for its appearance in starry southern skies. City lights about 200 kilometers distant still glow along the horizon at the right, while bright star Canopus shines above them in the cloudy sky.

Image credit: Yuri Beletsky
Hoag's Object: A Strange Ring Galaxy (2013-07-28)

Is this one galaxy or two?  This question came to light in 1950 when astronomer Art Hoag chanced upon this unusual extragalactic object.  On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older.  Between the two is a gap that appears almost completely dark.  How Hoag's Object formed remains unknown, although similar objects have now been identified and collectively labeled as a form of ring galaxy.  Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. The above photo taken by the Hubble Space Telescope in July 2001 revealed unprecedented details of Hoag's Object. More recent observations in radio waves indicate that Hoag's Object has not accreted a smaller galaxy in the past billion years.  Hoag's Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens).  Coincidentally, visible in the gap (at about one o'clock) is yet another ring galaxy that likely lies far in the distance.   Follow APOD on: Facebook (Daily) (Sky) (Spanish) or Google Plus (Daily) (River)
Saturn, Titan, Rings, and Haze (2013-07-29)

This is not a solar eclipse. Pictured above is a busy vista of moons and rings taken at Saturn. The large circular object in the center of the image is Titan, the largest moon of Saturn and one of the most intriguing objects in the entire Solar System. The dark spot in the center is the main solid part of the moon.  The bright surrounding ring is atmospheric haze above Titan, gas that is scattering sunlight to a camera operating onboard the robotic Cassini spacecraft. Cutting horizontally across the image are the rings of Saturn, seen nearly edge on.  At the lower right of Titan is Enceladus, a small moon of Saturn. Since the image was taken pointing nearly at the Sun, the surfaces of Titan and Enceladus appear in silhouette, and the rings of Saturn appear similar to a photographic negative. Now if you look really really closely at Enceladus, you can see a hint of icy jets shooting out toward the bottom of the image. It is these jets that inspired future proposals to land on Enceladus, burrow into the ice, and search for signs of extraterrestrial life.
NGC 2392 from Hubble and Chandra (2013-07-30)

In 1787, astronomer William Herschel discovered the NGC 2392.  From the ground, NGC 2392 resembles a person's head surrounded by a parka hood.  In 2000, the Hubble Space Telescope imaged NGC 2392 in visible light, while the nebula was imaged in X-rays by the Chandra X-ray Observatory in 2007. The above combined visible-X ray image, with X-rays emitted by central hot gas and shown in pink, was released last week. From space, the nebula displays gas clouds so complex they are not fully understood.  NGC 2392 is clearly a planetary nebula, and the gas seen above composed the outer layers of a Sun-like star only 10,000 years ago.  The inner filaments visible above are being ejected by strong wind of particles from the central star.  The outer disk contains unusual light-year long orange filaments. NGC 2392 Nebula spans about 1/3 of a light year and lies in our Milky Way Galaxy, about 3,000 light years distant, toward the constellation of the Twins (Gemini).
130 Years of Earth Surface Temperatures (2013-07-31)

How has the surface temperature of Earth been changing? To help find out, Earth scientists collected temperature records from over 1000 weather stations around the globe since 1880, and combined them with modern satellite data. The above movie dramatizes the result showing 130 years of planet-wide temperature changes relative to the local average temperatures in the mid-1900s. In the above global maps, red means warmer and blue means colder. On average, the display demonstrates that the temperature on Earth has increased by nearly one degree Celsius over the past 130 years, and many of the warmest years on record have occurred only recently. Global climate change is of more than passing interest -- it is linked to global weather severity and coastal sea water levels.
Moon Over Andromeda (2013-08-01)

The Great Spiral Galaxy in Andromeda (aka M31), a mere 2.5 million light-years distant, is the closest large spiral to our own Milky Way. Andromeda is visible to the unaided eye as a small, faint, fuzzy patch, but because its surface brightness is so low, casual skygazers can't appreciate the galaxy's impressive extent in planet Earth's sky. This entertaining composite image compares the angular size of the nearby galaxy to a brighter, more familiar celestial sight. In it, a deep exposure of Andromeda, tracing beautiful blue star clusters in spiral arms far beyond the bright yellow core, is combined with a typical view of a nearly full Moon. Shown at the same angular scale, the Moon covers about 1/2 degree on the sky, while the galaxy is clearly several times that size. The deep Andromeda exposure also includes two bright satellite galaxies, M32 and M110 (bottom).

Image credit: Adam Block
Tropic of Cancer (2013-08-02)

This intriguing monument can be found in Taiwan between the cities of Hualian and Taitong. Split into two sides, it straddles a special circle of latitude on planet Earth, near 23.5 degrees north, known as the Tropic of Cancer. Points along the Tropic of Cancer are the northernmost locations where the Sun can pass directly overhead, an event that occurs once a year during the northern hemisphere's summer solstice. The latitude that defines the Tropic of Cancer corresponds to the tilt of planet Earth's rotation axis with respect to its orbital plane. The name refers to the zodiacal constellation Cancer the Crab. Historically the Sun's position was within Cancer during the northern summer solstice, but because of the precession of Earth's axis, that solstice Sun is currently within the boundaries of Taurus. In this starry night scene the otherwise all white structure is colored by city lights, with its orange side just south of the Tropic of Cancer and the white side just north. Of course, there is a southern hemisphere counterpart of the Tropic of Cancer. It's called the Tropic of Capricorn.

Image credit: Rogelio Bernal Andreo
Twisting with NGC 3718 (2013-08-03)

A careful look at this colorful cosmic snapshot reveals a surprising number of galaxies both near and far toward the constellation Ursa Major. The most striking is NGC 3718, the warped spiral galaxy near picture center. NGC 3718's spiral arms look twisted and extended, mottled with young blue star clusters. Drawn out dust lanes obscure its yellowish central regions. A mere 150 thousand light-years to the right is another large spiral galaxy, NGC 3729. The two are likely interacting gravitationally, accounting for the peculiar appearance of NGC 3718. While this galaxy pair lies about 52 million light-years away, the remarkable Hickson Group 56 can also be seen clustered above NGC 3718, near the top of the frame. Hickson Group 56 consists of five interacting galaxies and lies over 400 million light-years away. This picture was chosen as the overall winner in the 2013 David Malin Astrophotography Competition.

Image credit: Ursa Major
Io's Surface: Under Construction (2013-08-04)

Like the downtown area of your favorite city and any self-respecting web site ... Io's surface is constantly under construction. This moon of Jupiter holds the distinction of being the Solar System's most volcanically active body -- its bizarre looking surface continuously formed and reformed by lava flows. Generated using 1996 data from NASA's Galileo spacecraft, this high resolution composite image is centered on the side of Io that always faces away from Jupiter. It has been enhanced to emphasize Io's surface brightness and color variations, revealing features as small as 1.5 miles across. The notable absence of impact craters suggests that the entire surface is covered with new volcanic deposits much more rapidly than craters are created. What drives this volcanic powerhouse? A likely energy source is the changing gravitational tides caused by Jupiter and the other Galilean moons as Io orbits the massive gas giant planet. Heating Io's interior, the pumping tides would generate the sulfurous volcanic activity.
Leaving Earth (2013-08-05)

What it would look like to leave planet Earth? Such an event was recorded visually in great detail by the MESSENGER spacecraft as it swung back past the Earth, eight years ago, on its way in toward the planet Mercury. Earth can be seen rotating in this time-lapse video, as it recedes into the distance. The sunlit half of Earth is so bright that background stars are not visible. The robotic MESSENGER spacecraft is now in orbit around Mercury and has recently concluded the first complete map of the surface. On occasion, MESSENGER has continued to peer back at its home world. MESSENGER is one of the few things created on the Earth that has left and will never return -- at the end of its mission MESSENGER will be crashed into Mercury's surface.
In the Vicinity of the Cone Nebula (2013-08-06)

Strange shapes and textures can be found in neighborhood of the Cone Nebula. The unusual shapes originate from fine interstellar dust reacting in complex ways with the energetic light and hot gas being expelled by the young stars.  The brightest star on the right of the above picture is S Mon, while the region just below it has been nicknamed the Fox Fur Nebula for its color and structure. The blue glow directly surrounding S Mon results from reflection, where neighboring dust reflects light from the bright star. The red glow that encompasses the whole region results not only from dust reflection but also emission from hydrogen gas ionized by starlight. S Mon is part of a young open cluster of stars named NGC 2264, located about 2500 light years away toward the constellation of the Unicorn (Monoceros).   Even though it points right at S Mon, details of the origin of the mysterious geometric Cone Nebula, visible on the far left, remain a mystery.
Meteors and Aurorae over Iceland (2013-08-07)

What's going on behind that mountain? Quite a bit.  First of all, the mountain itself, named Kirkjufell, is quite old and located in western Iceland near the town of Grundarfj�r�ur. In front of the steeply-sloped structure lies a fjord that had just begun to freeze when the above image was taken -- in mid-December of 2012. Although quite faint to the unaided eye, the beautiful colors of background aurorae became quite apparent on the 25-second exposure. What makes this image is of particular note, though, is that it also captures streaks from the Geminids meteor shower -- meteors that might not have been evident were the aurora much brighter. Far in the distance, on the left, is the band of our Milky Way Galaxy, while stars from our local part of the Milky Way appear spread across the background.  This weekend the Perseids meteor shower will peak and may well provide sky enthusiasts with their own memorable visual experiences.   Follow APOD on: Facebook (Daily) (Sky) (Spanish) or Google Plus (Daily) (River)

Image credit: James Boardman-Woodend 
(Images ~ Inspired by Nature);
 Annotation:  Judy Schmidt
NGC 3370: A Sharper View (2013-08-08)

Similar in size and grand design to our own Milky Way, spiral galaxy NGC 3370 lies about 100 million light-years away toward the constellation Leo. Recorded here in exquisite detail by the Hubble Space Telescope's Advanced Camera for Surveys, the big, beautiful face-on spiral does steal the show, but the sharp image also reveals an impressive array of background galaxies in the field, strewn across the more distant Universe. Looking within NGC 3370, the image data has proved sharp enough to study individual pulsating stars known as Cepheids that can be used to accurately determine this galaxy's distance. NGC 3370 was chosen for this study because in 1994 the spiral galaxy was also home to a well studied stellar explosion -- a type Ia supernova. Combining the known distance to this standard candle supernova, based on the Cepheid measurements, with observations of supernovae at even greater distances, can reveal the size and expansion rate of the Universe itself.   Gallery: Recent supernova in nearby spiral M74
Perseid over Albrechtsberg Castle (2013-08-09)

Medieval Albrechtsberg castle is nestled in trees near the northern bank of the river Pielach and the town of Melk, Austria. In clearing night skies on August 12, 2012 it stood under constellations of the northern summer, including Aquarius, Aquila, and faint, compact Delphinus (above and right of center) in this west-looking skyview. The scene also captures a bright meteor above the castle walls. Part of the annual perseid meteor shower, its trail points back toward the heroic constellation Perseus high above the horizon in the early morning hours. Entering the atmosphere at about 60 kilometers per second, perseid meteors are swept up dust grains from the tail of comet Swift-Tuttle. Of course, this year's perseid meteors will flash through night skies this weekend.

Image credit: Sebastian Voltmer
Perseids over Meteora (2013-08-10)

The two bright meteors flashing through this night skyscape from August 7 are part of the ongoing Perseid meteor shower. In the direction indicated by both colorful streaks, the shower's radiant in the eponymous constellation Perseus is at the upper right. North star Polaris, near the center of all the short, arcing star trails is at the upper left. But also named for its pose against the sky, the monastery built on the daunting sandstone cliffs in the foreground is part of Meteora. A World Heritage site, Meteora is a historic complex of lofty monasteries located near Kalabaka in central Greece.

Image credit: Babak Tafreshi
M74: The Perfect Spiral (2013-08-11)

If not perfect, then this spiral galaxy is at least one of the most photogenic. An island universe of about 100 billion stars, 32 million light-years away toward the constellation Pisces, M74 presents a gorgeous face-on view. Classified as an Sc galaxy, the grand design of M74's graceful spiral arms are traced by bright blue star clusters and dark cosmic dust lanes. Constructed from image data recorded in 2003 and 2005, this sharp composite is from the Hubble Space Telescope's Advanced Camera for Surveys. Spanning about 30,000 light-years across the face of M74, it includes exposures recording emission from hydrogen atoms, highlighting the reddish glow of the galaxy's large star-forming regions. Recently, many astronomers are tracking a bright supernova that has been seen in M74.   Gallery: Highlights of the 2013 Perseids Meteor Shower
Orbits of Potentially Hazardous Asteroids (2013-08-12)

Are asteroids dangerous? Some are, but the likelihood of a dangerous asteroid striking the Earth during any given year is low. Because some past mass extinction events have been linked to asteroid impacts, however, humanity has made it a priority to find and catalog those asteroids that may one day affect life on Earth. Pictured above are the orbits of the over 1,000 known Potentially Hazardous Asteroids (PHAs). These documented tumbling boulders of rock and ice are over 140 meters across and will pass within 7.5 million kilometers of Earth -- about 20 times the distance to the Moon. Although none of them will strike the Earth in the next 100 years -- not all PHAs have been discovered, and past 100 years, many orbits become hard to predict. Were an asteroid of this size to impact the Earth, it could raise dangerous tsunamis, for example. Of course rocks and ice bits of much smaller size strike the Earth every day, usually pose no danger, and sometimes creating memorable fireball and meteor displays.    Gallery: Highlights of the 2013 Perseids Meteor Shower
Perseid Meteors Over Ontario (2013-08-13)

Where are all of these meteors coming from?  In terms of direction on the sky, the pointed answer is the constellation of Perseus.  That is why the meteor shower that peaked over the past few days is known as the Perseids -- the meteors all appear to come from a radiant toward Perseus. Three dimensionally, however, sand-sized debris expelled from Comet Swift-Tuttle follows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the Perseus. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Perseus. Pictured above, a composite of 13 early images from this year's Pereids meteor shower shows many bright meteors that streaked through the sky the night of August 11 near Oakland, Ontario, Canada.    Gallery: Highlights of the 2013 Perseids Meteor Shower

Image credit: Darryl Van Gaal;
 Annotation:  Judy Schmidt
Moonset from Taiwan (2013-08-14)

It took three worlds to create this simple image. The first world was the Earth, which was quite prominent. The dividing line running horizontally below the middle separates sea from sky. On this part of the Earth, it was almost nighttime. The second world was the Moon, which was almost invisible. The Moon had its unilluminated half masked by the red sunset glow of Earth's sky. A thin sliver of the new Moon was visible, a crescent that traces the bright curving line. The third world was the Sun, which does not appear directly. All of the light recorded in the image originated from the Sun. The above half-second exposure was taken last week from Anping, Taiwan. A few minutes after this image was taken the Earth had spun just a little bit further -- forcing the Moon to follow the Sun into the sea -- and the horizon to become dark.   Astrophysicists: Browse 600+ codes in the Astrophysics Source Code Library

Image credit: Hung-Hsuan Yen
The Magellanic Stream (2013-08-15)

In an astronomical version of the search for the source of the Nile, astronomers now have strong evidence for the origin of the Magellanic Stream. This composite image shows the long ribbon of gas, discovered at radio wavelengths in the 1970s, in pinkish hues against an optical all-sky view across the plane of our Milky Way galaxy. Both Large and Small Magellanic Clouds, dwarf satellite galaxies of the the Milky Way, are seen near the head of the stream at the right. Data from Hubble's Cosmic Origins Spectrograph were used to explore abundances of elements along sightlines to quasars that intersect the stream. The results indicate that most of the stream's material comes from the Small Magellanic Cloud. The Magellanic Stream is likely the result of gravitational tidal interactions between the two dwarf galaxies some 2 billion years ago, the Small Magellanic Cloud losing more material in the encounter because of its lower mass.   Gallery: New Bright Nova in Delphinus