juliensimon/nasa-apod huggingface dataset:
Eclipse Across America: Path Prediction Video (2017-06-19)

Where will you be during the Eclipse across America? On August 21, the shadow of the Moon will cross the continental USA for the first time since 1979. The predicted path -- a certainty given modern astronomical knowledge -- is shown in the featured NASA video.  Most people in the USA will be within a day's drive to the path of the total solar eclipse, while the rest of North America will see a partial solar eclipse. In the path of totality, given clear-enough skies, the Moon will block out the Sun making it eerily dark for as long as 2 minutes and 40 seconds.  If interested in attending an eclipse party, please contact your local amateur astronomical society, science center, park, or university to see if one is already being planning. Some eclipse chasers have traveled to the end of the world to see a total eclipse of the Sun, and along the way have recorded many entertaining adventure stories.
The Massive Stars in Westerlund 1 (2017-06-20)

Star cluster Westerlund 1 is home to some of the largest and most massive stars known. It is headlined by the star Westerlund 1-26, a red supergiant star so big that if placed in the center of our Solar System, it would extend out past the orbit of Jupiter. Additionally, the young star cluster is home to 3 other red supergiants, 6 yellow hypergiant stars, 24 Wolf-Rayet stars, and several even-more unusual stars that continue to be studied.  Westerlund 1 is relatively close-by for a star cluster at a distance of 15,000 light years, giving astronomers a good laboratory to study the development of massive stars. The featured image of Westerlund 1 was taken by the Hubble Space Telescope toward the southern constellation of the Altar (Ara). Although presently classified as a "super" open cluster, Westerlund 1 may evolve into a low mass globular cluster over the next billion years.    Follow APOD on: Facebook,  Google Plus,  Instagram, or Twitter
A Sundial that Shows Solstice (2017-06-21)

What day is it? If the day -- and time -- are right, this sundial will tell you: SOLSTICE. Only then will our  Sun be located just right for sunlight to stream through openings and spell out the term for the longest and shortest days of the year. But this will happen today (and again in December). The sundial was constructed by Jean Salins in 1980 and is situated at the Ecole Sup�rieure des Mines de Paris in Valbonne Sophia Antipolis of south-eastern France. On two other days of the year, watchers of this sundial might get to see it produce another word: EQUINOXE.

Image credit: Jean-Marc Mari
Northern Summer on Titan (2017-06-22)

While yesterday's solstice brought summer to planet Earth's northern hemisphere, a northern summer solstice arrived for ringed planet Saturn nearly a month ago on May 24. Following the Saturnian seasons, its large moon Titan was captured in this Cassini spacecraft image from June 9. The near-infrared view finds bright methane clouds drifting through Titan's northern summer skies as seen from a distance of about 507,000 kilometers. Below Titan's clouds, dark hydrocarbon lakes sprawl near the large moon's now illuminated north pole.
Solstice Conjunction over Budapest (2017-06-23)

Before a solstice Sun rose on June 21, brilliant Venus and an old crescent Moon posed together over Budapest, Hungary for this predawn skyscape. In the foreground the view looks across the Danube river from Buda to Pest toward the dome and peaks of the Hungarian Parliament building. Low clouds are in silhouette against a twilight sky. But far enough above the eastern horizon to catch the sunlight shines another seasonal apparition on that solstice morning, noctilucent clouds. Seen near sunrise and sunset in summer months at high latitudes, the night-shining clouds are formed as water vapor in the cold upper atmosphere condenses on meteoric dust or volcanic ash near the edge of space.

Image credit: György
Soponyai
Markarian's Chain to Messier 64 (2017-06-24)

Top to bottom, this colorful and broad telescopic mosaic links Markarian's Chain of galaxies across the core of the Virgo Cluster to dusty spiral galaxy Messier 64. Galaxies are scattered through the field of view that spans some 20 full moons across a gorgeous night sky. The cosmic frame is also filled with foreground stars from constellations Virgo and the well-groomed Coma Berenices, and faint, dusty nebulae drifting above the plane of the Milky Way. Look carefully for Markarian's eyes. The famous pair of interacting galaxies is near the top, not far from M87, the Virgo cluster's giant elliptical galaxy. At the bottom, you can stare down Messier 64, also known as the Black Eye Galaxy. The Virgo Cluster is the closest large galaxy cluster to our own local galaxy group. Virgo Cluster galaxies are about 50 million light-years distant, but M64 lies a mere 17 million light-years away.

Image credit: Rogelio Bernal
Andreo
The N44 Superbubble (2017-06-25)

What created this gigantic hole?  The vast emission nebula N44 in our neighboring galaxy the Large Magellanic Cloud has a large, 250 light-year hole and astronomers are trying to figure out why.  One possibility is particle winds expelled by massive stars in the bubble's interior that are pushing out the glowing gas.  This answer was found to be inconsistent with measured wind velocities, however.  Another possibility is that the expanding shells of old supernovas have sculpted the unusual space cavern.   An unexpected clue of hot X-ray emitting gas was recently been detected escaping the N44 superbubble.  The featured image was taken in three very specific colors by the huge 8-meter Gemini South Telescope on Cerro Pachon in Chile.    Follow APOD on: Facebook,  Google Plus,  Instagram, or Twitter

Image credit: Gemini Obs.
Artistic Impression: The Surface of TRAPPIST-1f (2017-06-26)

If you could stand on the surface of the newly discovered Earth-sized exoplanet TRAPPIST-1f, what would you see? Presently, no Earthling knows for sure, but the featured illustration depicts a reasoned guess based on observational data taken by NASA's Sun-orbiting Spitzer Space Telescope. In 2017, four more Earth-sized planets were found by Spitzer, including TRAPPIST-1f, in addition to three discovered in 2015 from the ground.  From the planet's surface, near the mild terminator between night and day, you might see water, ice, and rock on the ground, while water-based clouds might hover above. Past the clouds, the small central star TRAPPIST-1 would appear more red than our Sun, but angularly larger due to the close orbit. With seven known Earth-sized planets -- many of which pass near each other -- the TRAPPIST-1 system is not only a candidate to have life, but intercommunicating life -- although a preliminary search has found no obvious transmissions.
The M81 Galaxy Group through the Integrated Flux Nebula (2017-06-27)

Distant galaxies and nearby nebulas highlight this deep image of the M81 Group of galaxies.  First and foremost in this 80-exposure mosaic is the grand design spiral galaxy M81, the largest galaxy in the image, visible on the lower right. M81 is gravitationally interacting with M82 just above it, a large galaxy with an unusual halo of filamentary red-glowing gas.  Around the image many other galaxies from the M81 Group of galaxies can be seen, as well as many foreground Milky Way stars.  This whole galaxy menagerie is seen through the glow of an Integrated Flux Nebula (IFN), a vast and complex screen of diffuse gas and dust also in our Milky Way Galaxy. Details of the red and yellow IFN, digitally enhanced, were imaged by a new wide-field camera recently installed at the Teide Observatory in the Canary Islands of Spain.   Free Presentation (with Czech translation): APOD Editor to speak in Prague on June 30

Image credit: IAC
Composite Messier 20 and 21 (2017-06-28)

The beautiful Trifid Nebula, also known as Messier 20, lies about 5,000 light-years away, a colorful study in cosmic contrasts. It shares this nearly 1 degree wide field with open star cluster Messier 21 (top left). Trisected by dust lanes the Trifid itself is about 40 light-years across and a mere 300,000 years old. That makes it one of the youngest star forming regions in our sky, with newborn and embryonic stars embedded in its natal dust and gas clouds. Estimates of the distance to open star cluster M21 are similar to M20's, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. M21's stars are much older, about 8 million years old. M20 and M21 are easy to find with even a small telescope in the nebula rich constellation Sagittarius. In fact, this well-composed scene is a composite from two different telescopes. Using narrowband data it blends a high resolution image of M20 with a wider field image extending to M21.

Image credit: Martin Pugh
Symbiotic R Aquarii (2017-06-29)

A long recognized naked-eye variable star, R Aquarii is actually an interacting binary star system, two stars that seem to have a close, symbiotic relationship. About 710 light years away, it consists of a cool red giant star and hot, dense white dwarf star in mutual orbit around their common center of mass. The binary system's visible light is dominated by the red giant, itself a Mira-type long period variable star. But material in the cool giant star's extended envelope is pulled by gravity onto the surface of the smaller, denser white dwarf, eventually triggering a thermonuclear explosion and blasting material into space. Optical image data (red) shows the still expanding ring of debris originating from a blast that would have been seen in the early 1770s. The evolution of less understood energetic events producing high energy emission in the R Aquarii system has been monitored since 2000 using Chandra X-ray Observatory data (blue). The composite field of view is less that a light-year across at the estimated distance of R Aquarii.
NGC 7814: The Little Sombrero in Pegasus (2017-06-30)

Point your telescope toward the high flying constellation Pegasus and you can find this expanse of Milky Way stars and distant galaxies. Dominated by NGC 7814, the pretty field of view would almost be covered by a full moon. NGC 7814 is sometimes called the Little Sombrero for its resemblance to the brighter more famous M104, the Sombrero Galaxy. Both Sombrero and Little Sombrero are spiral galaxies seen edge-on, and both have extensive halos and central bulges cut by a thin disk with thinner dust lanes in silhouette. In fact, NGC 7814 is some 40 million light-years away and an estimated 60,000 light-years across. That actually makes the Little Sombrero about the same physical size as its better known namesake, appearing smaller and fainter only because it is farther away. Very faint dwarf galaxies, potentially satellites of NGC 7814, have been discovered in deep exposures of the Little Sombrero.

Image credit: CHART32 Team
3D Lava Falls of Mars (2017-07-01)

Get out your red/cyan glasses and gaze across lava falls of Mars. The stereo anaglyph was created by combining two images recorded by the HiRISE camera onboard Mars Reconnaissance Orbiter. The multi-level falls were created as flowing lava breached sections of the northern rim of a 30-kilometer diameter martian crater, located in the western part of the Red Planet's volcanic Tharsis region. As the molten lava cascaded down the crater wall and terraces to reach the crater floor it left the distinctly rough, fan-shaped flows on the steeper slopes. North is up and the breathtaking 3D view is 5 kilometers wide.
Mountains of Dust in the Carina Nebula (2017-07-02)

It's stars versus dust in the Carina Nebula and the stars are winning. More precisely, the energetic light and winds from massive newly formed stars are evaporating and dispersing the dusty stellar nurseries in which they formed. Located in the Carina Nebula and known informally as Mystic Mountain, these pillar's appearance is dominated by the dark dust even though it is composed mostly of clear hydrogen gas. Dust pillars such as these are actually much thinner than air and only appear as mountains due to relatively small amounts of opaque interstellar dust.  About 7,500 light-years distant, the featured image was taken with the Hubble Space Telescope and highlights an interior region of Carina which spans about three light years. Within a few million years, the stars will likely win out completely and the entire dust mountain will evaporate.
The Summer Triangle over the Great Wall (2017-07-03)

Have you ever seen the Summer Triangle? The bright stars Vega, Deneb, and Altair form a large triangle on the sky that can be seen rising in the northern spring during the morning, and rising in the northern fall during the evening.  During summer months, the triangle can be found nearly overhead near midnight as three of the brightest stars on the sky.  Featured here, along with the arch of the central band of our Milky Way Galaxy, the Summer Triangle asterism was captured this spring over the Great Wall of China. This part of the Great Wall, a World Culture Heritage Site, was built during the 6th century on the Yan Mountains. At the summit is Wangjinglou Tower from which, on a clear night, the lights of Beijing are visible in the distance.

Image credit: Steed Yu & NightChina.net
Celestial Fireworks: Into Star Cluster Westerlund 2 (2017-07-04)

What if you could go right into a cluster where stars are forming? A one-minute, time-lapse, video visualization of just this has been made with 3D computer modeling of the region surrounding the star cluster Westerlund 2, based on images from the Hubble Space Telescope in visible and infrared light. Westerlund 2 spans about 10 light years across and lies about 20,000 light years distant toward the constellation of the Ship's Keel (Carina). As the illustrative animation begins, the greater Gum 29 nebula fills the screen, with the young cluster of bright stars visible in the center.  Stars zip past you as you approach the cluster. Soon your imaginary ship pivots and you pass over light-year long pillars of interstellar gas and dust.  Strong winds and radiation from massive young stars destroy all but the densest nearby dust clumps, leaving these pillars in their shadows -- many pointing back toward the cluster center. Last, you pass into the top of the star cluster and survey hundreds of the most massive stars known.    Open Science: Browse 1,500+ codes in the Astrophysics Source Code Library
Aphelion Sunrise (2017-07-05)

On July 3rd, planet Earth reached aphelion, the farthest point in its elliptical orbit around the Sun. Each year, this day of the most distant Sun happens to occur during winter in the southern hemisphere. That's where this aphelion sunrise from 2015 was captured in a time series composite against the skyline of Brisbane, Australia. Of course, seasons for our fair planet are not determined by distance to the Sun, but by the tilt of Earth's rotational axis with respect to the ecliptic, the plane of its orbit. Fondly known as the obliquity of the ecliptic, the angle of the tilt is about 23.4 degrees from perpendicular to the orbital plane. So the most distant sunrise occurs during northern summer, when the planet's north pole is tilted toward the Sun and the north enjoys longer, warmer days.

Image credit: Stephen Mudge
Atlas, Daphnis, and Pan (2017-07-06)

Atlas, Daphnis, and Pan are small, inner, ring moons of Saturn, shown at the same scale in this montage of images from the still Saturn-orbiting Cassini spacecraft. In fact, Daphnis was discovered in Cassini images from 2005. Atlas and Pan were first sighted in images from the Voyager 1 and 2 spacecraft. Flying saucer-shaped Atlas orbits near the outer edge of Saturn's bright A Ring while Daphnis orbits inside the A Ring's narrow Keeler Gap and Pan within the A Ring's larger Encke Gap. The curious equatorial ridges of the small ring moons could be built up by the accumulation of ring material over time. Even diminutive Daphnis makes waves in the ring material as it glides along the edge of the Keeler Gap.
A View Toward M106 (2017-07-07)

Big, bright, beautiful spiral, Messier 106 dominates this cosmic vista. The two degree wide telescopic field of view looks toward the well-trained constellation Canes Venatici, near the handle of the Big Dipper. Also known as NGC 4258, M106 is about 80,000 light-years across and 23.5 million light-years away, the largest member of the Canes II galaxy group. For a far away galaxy, the distance to M106 is well-known in part because it can be directly measured by tracking this galaxy's remarkable maser, or microwave laser emission. Very rare but naturally occuring, the maser emission is produced by water molecules in molecular clouds orbiting its active galactic nucleus. Another prominent spiral galaxy on the scene, viewed nearly edge-on, is NGC 4217 below and right of M106. The distance to NGC 4217 is much less well-known, estimated to be about 60 million light-years.

Image credit: Peter Feltoti
Hidden Galaxy IC 342 (2017-07-08)

Similar in size to large, bright spiral galaxies in our neighborhood, IC 342 is a mere 10 million light-years distant in the long-necked, northern constellation Camelopardalis. A sprawling island universe, IC 342 would otherwise be a prominent galaxy in our night sky, but it is hidden from clear view and only glimpsed through the veil of stars, gas and dust clouds along the plane of our own Milky Way galaxy. Even though IC 342's light is dimmed by intervening cosmic clouds, this sharp telescopic image traces the galaxy's own obscuring dust, blue star clusters, and glowing pink star forming regions along spiral arms that wind far from the galaxy's core. IC 342 may have undergone a recent burst of star formation activity and is close enough to have gravitationally influenced the evolution of the local group of galaxies and the Milky Way.

Image credit: T. Rector
Earth at Night (2017-07-09)

Can you find your favorite country or city?  Surprisingly, on this world-wide nightscape, city lights make this task quite possible.  Human-made lights highlight particularly developed or populated areas of the Earth's surface, including the seaboards of Europe, the eastern United States, and Japan.  Many large cities are located near rivers or oceans so that they can exchange goods cheaply by boat.  Particularly dark areas include the central parts of South America, Africa, Asia, and Australia.  The featured composite was created from images that were collected during cloud-free periods in April and October 2012 by the Suomi-NPP satellite, from a polar orbit about 824 kilometers above the surface, using its Visible Infrared Imaging Radiometer Suite (VIIRS).
Spiral Galaxy NGC 1512: The Nuclear Ring (2017-07-10)

What's happening around the center of this spiral galaxy? Seen in total, NGC 1512 appears to be a barred spiral galaxy -- a type of spiral that has a straight bar of stars across its center.  This bar crosses an inner ring, though, a ring not seen as it surrounds the pictured region. Featured in this Hubble Space Telescope image is a "nuclear ring" -- one that surrounds the nucleus of the spiral.  The two rings are connected not only by a bar of bright stars but by dark lanes of dust. Inside of this nuclearring, dust continues to spiral right into the very center -- possibly the location of a large black hole. The rings are bright with newly formed stars.
Star Cluster Omega Centauri in HDR (2017-07-11)

Behold the largest ball of stars in our galaxy. Omega Centauri is packed with about 10 million stars, many older than our Sun and packed within a volume of only about 150 light-years in diameter. The star cluster is the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way. The featured image shows so many stars because it merged different exposures with high dynamic range (HDR) techniques.  Omega Centauri, also known as NGC 5139, lies about 15,000 light-years away toward the southern constellation of the Centaurus.

Image credit: Mike O'Day
Messier 63: The Sunflower Galaxy (2017-07-12)

A bright spiral galaxy of the northern sky, Messier 63 is about 25 million light-years distant in the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across. That's about the size of our own Milky Way Galaxy. Known by the popular moniker, The Sunflower Galaxy, M63 sports a bright yellowish core in this sharp composite image from space- and ground-based telescopes. Its sweeping blue spiral arms are streaked with cosmic dust lanes and dotted with pink star forming regions. A dominant member of a known galaxy group, M63 has faint, extended features that are likely star streams from tidally disrupted satellite galaxies. M63 shines across the electromagnetic spectrum and is thought to have undergone bursts of intense star formation.

Image credit: Hubble Legacy Archive
Full Moon and Boston Light (2017-07-13)

This well-planned telephoto timelapse captures July's Full Moon rise across outer Boston Harbor, Massachusetts, planet Earth. In the foreground, the historic terrestrial beacon is known as Boston Light. July's Full Moon is known to some as a Thunder Moon, likely a reference to the sounds of the northern summer month's typically stormy weather. But the eastern sky was clear for this video sequence. Near the horizon, the long sight-line through atmospheric layers filters and refracts the moonlight, causing the rising Moon's reddened color, ragged edges and distorted shape.

Image credit: Babak Tafreshi
NGC 4449: Close-up of a Small Galaxy (2017-07-14)

Grand spiral galaxies often seem to get all the glory. Their young, blue star clusters and pink star forming regions along sweeping spiral arms are guaranteed to attract attention. But small irregular galaxies form stars too, like NGC 4449, about 12 million light-years distant. Less than 20,000 light-years across, the small island universe is similar in size, and often compared to our Milky Way's satellite galaxy, the Large Magellanic Cloud (LMC). This remarkable Hubble Space Telescope close-up of the well-studied galaxy was reprocessed to highlight the telltale reddish glow of hydrogen gas. The glow traces NGC 4449's widespread star forming regions, some even larger than those in the LMC, with enormous interstellar arcs and bubbles blown by short-lived, massive stars. NGC 4449 is a member of a group of galaxies found in the constellation Canes Venatici. It also holds the distinction of being the first dwarf galaxy with an identified tidal star stream.

Image credit: Hubble Legacy Archive
Close-up of The Great Red Spot (2017-07-15)

On July 11, the Juno spacecraft once again swung near to Jupiter's turbulent cloud tops in its looping 53 day orbit around the Solar System's ruling gas giant. About 11 minutes after perijove 7, its closest approach on this orbit, it passed directly above Jupiter's Great Red Spot. During the much anticipated fly over, it captured this close-up image data from a distance of less than 10,000 kilometers. The raw JunoCam data was subsequently processed by citizen scientists. Very long-lived but found to be shrinking, the Solar System's largest storm system was measure to be 16,350 kilometers wide on April 15. That's about 1.3 times the diameter of planet Earth.