juliensimon/nasa-apod huggingface dataset:
A Total Solar Eclipse of Saros 145 (2017-08-11)

A darkened sky holds bright planet Venus, the New Moon in silhouette, and the shimmering corona of the Sun in this image of a total solar eclipse. A composite of simultaneous telephoto and wide angle frames it was taken in the path of totality 18 years ago, August 11, 1999, near Kastamonu, Turkey. That particular solar eclipse is a member of Saros 145. Known historically from observations of the Moon's orbit, the Saros cycle predicts when the Sun, Earth, and Moon will return to the same geometry for a solar (or lunar) eclipse. The Saros has a period of 18 years, 11 and 1/3 days. Eclipses separated by one Saros period belong to the same numbered Saros series and are very similar. But the path of totality for consecutive solar eclipses in the same Saros shifts across the Earth because the planet rotates for an additional 8 hours during the cycle's fractional day. So the next solar eclipse of Saros 145 will also be a total eclipse, and the narrow path of totality will track coast to coast across the United States on August 21, 2017.

Image credit: Tunç Tezel
A Day in the Life of a (mostly) Human Sundial (2017-08-12)

Have you ever wanted to be a gnomon? Of course, a gnomon is the tall part of a sundial that casts a shadow. The gnomon's shadow moves as the Sun moves across the sky, indicating time by the shadow's position on the dial face. So on July 19th, the Astronomy Group of the Progymnasium Rosenfeld created a human sundial, each participant patiently playing the role of the gnomon for 10 minutes. In this timelapse video of their temporal voyage of discovery, one image was taken every 20 seconds from 8 am until 4 pm Central European Summer Time. Drawn on the ground are the dial hour marks calculated to show the local time for that specific date. Behind, the tower clock offers a time check. Can you find the local time of solar noon? (Hint: At solar noon the Sun is on the meridan.) The persistent group plans a repetition of the human sundial performance next winter to compare the length of the day and the altitude of the Sun.

Image credit: Progymnasium Rosenfeld
Detailed View of a Solar Eclipse Corona (2017-08-13)

Only in the fleeting darkness of a total solar eclipse is the light of the solar corona easily visible. Normally overwhelmed by the bright solar disk, the expansive corona, the sun's outer atmosphere, is an alluring sight. But the subtle details and extreme ranges in the corona's brightness, although discernible to the eye, are notoriously difficult to photograph. Pictured here, however, using multiple images and digital processing, is a detailed image of the Sun's corona taken during the 2008 August total solar eclipse from Mongolia.  Clearly visible are intricate layers and glowing caustics of an ever changing mixture of hot gas and magnetic fields. Bright looping prominences appear pink just above the Sun's limb. A similar solar corona might be visible through clear skies in a thin swath across the USA during a total solar eclipse that occurs just one week from tomorrow.    Citizen Science: How to participate during the Aug. 21 eclipse.

Image credit: Miloslav Druckm�ller
(Brno U. of Tech.),
Martin Dietzel, Peter Aniol, Vojtech Ru�in
Charon Flyover from New Horizons (2017-08-14)

What if you could fly over Pluto's moon Charon -- what might you see? The New Horizons spacecraft did just this in 2015 July as it zipped past Pluto and Charon with cameras blazing.  The images recorded allowed for a digital reconstruction of much of Charon's surface, further enabling the creation of fictitious flights over Charon created from this data.  One such fanciful, minute-long, time-lapse video is shown here with vertical heights and colors of surface features digitally enhanced.  Your journey begins over a wide chasm that divides different types of Charon's landscapes, a chasm that might have formed when Charon froze through. You soon turn north and fly over a colorful depression dubbed Mordor that, one hypothesis holds, is an unusual remnant from an ancient impact.  Your voyage continues over an alien landscape rich with never-before-seen craters, mountains, and crevices.  The robotic New Horizons spacecraft has now been targeted at Kuiper Belt object 2014 MU 69, which it should zoom past on New Year's Day 2019.
Stars, Gas, and Dust Battle in the Carina Nebula (2017-08-15)

Chaos reigns in the Carina Nebula where massive stars form and die. Striking and detailed, this close-up of a portion of the famous nebula is a combination of light emitted by hydrogen (shown in red) and oxygen (shown in blue).  Dramatic dark dust knots and complex features revealed are sculpted by the winds and radiation of Carina's massive and energetic stars.  One iconic feature of the Carina Nebula is the dark V-shaped dust lane that occurs in the top half of the image. The Carina Nebula spans about 200 light years, lies about 7,500 light years distant, and is visible with binoculars toward the southern constellation of Carina. In a billion years after the dust settles -- or is destroyed, and the gas dissipates -- or gravitationally condenses, then only the stars will remain -- but not even the brightest ones.

Image credit: Bastien Foucher
Perseid by the Sea (2017-08-16)

Just after moonrise on August 12 this grain of cosmic sand fell by the sea, its momentary flash part of the annual Perseid Meteor Shower. To create the Perseid meteors, dust along the orbit of periodic comet Swift-Tuttle is swept up by planet Earth. The cometary debris plows through the atmosphere at nearly 60 kilometers per second and is quickly vaporized at altitudes of 100 kilometers or so. Perseid meteors are often bright and colorful, like the one captured in this sea and night skyscape. Against starry sky and faint Milky Way the serene view looks south and west across the Adriatic Sea, from the moonlit Dalmatian coast toward the island of Brac.

Image credit: Tamas Ladanyi
NGC 2442: Galaxy in Volans (2017-08-17)

Distorted galaxy NGC 2442 can be found in the southern constellation of the flying fish, (Piscis) Volans. Located about 50 million light-years away, the galaxy's two spiral arms extending from a pronounced central bar have a hook-like appearance in wide-field images. But this mosaicked close-up, constructed from Hubble Space Telescope and European Southern Observatory data, follows the galaxy's structure in amazing detail. Obscuring dust lanes, young blue star clusters and reddish star forming regions surround a core of yellowish light from an older population of stars. The sharp image data also reveal more distant background galaxies seen right through NGC 2442's star clusters and nebulae. The image spans about 75,000 light-years at the estimated distance of NGC 2442.

Image credit: Robert Gendler
Perseids over the Pyrénées (2017-08-18)

This mountain and night skyscape stretches across the French Pyrenees National Park on August 12, near the peak of the annual Perseid meteor shower. The multi-exposure panoramic view was composed from the Col d'Aubisque, a mountain pass, about an hour before the bright gibbous moon rose. Centered is a misty valley and lights from the region's Gourette ski station toward the south. Taken over the following hour, frames capturing some of the night's long bright perseid meteors were aligned against the backdrop of stars and Milky Way.

Image credit: Jean-Francois
Graffand
Total Solar Eclipse of 1979 (2017-08-19)

From cold, clear skies over Riverton, Manitoba, Canada, planet Earth, the solar corona surrounds the silhouette of the New Moon in this telescopic snapshot of the total solar eclipse of February 26, 1979. Thirty eight years ago, it was the last total solar eclipse visible from the contiguous United States. The narrow path of totality ran through the northwestern states of Washington, Oregon, Idaho, Montana, and North Dakota before crossing into Canadian provinces Saskatchewan, Manitoba, Ontario and Quebec. Following the upcoming August 21, 2017 total solar eclipse crossing the U.S. from coast to coast, an annular solar eclipse will be seen in the continental United States on October 14, 2023, visible along a route from Northern California to Florida. Then, the next total solar eclipse to touch the continental U.S. will track across 13 states from from Texas to Maine on April 8, 2024.

Image credit: Jimmy Westlake
Time-Lapse: A Total Solar Eclipse (2017-08-20)

Have you ever experienced a total eclipse of the Sun?  This time-lapse movie depicts such an eclipse in dramatic detail, seen from Australia in 2012. As the video begins, a slight dimming of the Sun and the surrounding Earth is barely perceptible. As the Moon moves to cover nearly the entire Sun, darkness sweeps in from the left -- the fully blocked part of the Sun.  At totality, only the bright solar corona extends past the edges of the Moon, and darkness surrounds you. Distant horizons are still bright, though, as they are not in the darkest part of the shadow.  At mid-totality the darkness dips to the horizon below the eclipsed Sun, created by the shadow cone -- a corridor of shadow that traces back to the Moon. As the total solar eclipse ends -- usually after a few minutes -- the process reverses and Moon's shadow moves off to the other side. Tomorrow afternoon's total solar eclipse -- visible as at least a partial eclipse over all of North America -- can be experienced at social gatherings, some of which are being organized by local libraries.    Tomorrow's Eclipse: Live NASA Streaming Video

Image credit: Colin Legg
Milky Way over Chilean Volcanoes (2017-08-21)

Sometimes, the sky mimics the ground.  Taken in 2017 May from the Atacama Desert in Chile, the foreground of the featured image encompasses the dipping edge of the caldera of an extinct volcano. Poetically echoing the dip below is the arch of our Milky Way Galaxy above.  Many famous icons dot this southern nighttime vista, including the center of our Milky Way Galaxy on the far left, the bright orange star Antares also on the left, the constellation of the Southern Cross near the top of the arch, and the red-glowing Gum Nebula on the far right. Just above the horizon and splitting two distant volcanic peaks near the image center is the Large Magellanic Cloud -- the largest satellite galaxy of the Milky Way.    Today's Total Solar Eclipse: Live NASA Streaming Video

Image credit: Carlos Eduardo Fairbairn
A Total Solar Eclipse over Wyoming (2017-08-22)

Will the sky be clear enough to see the eclipse? This question was on the minds of many people attempting to view yesterday's solar eclipse. The path of total darkness crossed the mainland of the USA from coast to coast, from Oregon to South Carolina -- but a partial eclipse occurred above all of North America.  Unfortunately, many locations saw predominantly clouds. One location that did not was a bank of Green River Lake, Wyoming.  There, clouds blocked the Sun intermittantly up to one minute before totality. Parting clouds then moved far enough away to allow the center image of the featured composite sequence to be taken. This image shows the corona of the Sun extending out past the central dark Moon that blocks our familiar Sun. The surrounding images show the partial phases of the solar eclipse both before and after totality.

Image credit: Ben Cooper
The Crown of the Sun (2017-08-23)

During a total solar eclipse, the Sun's extensive outer atmosphere, or corona, is an inspirational sight. Streamers and shimmering features visible to the eye span a brightness range of over 10,000 to 1, making them notoriously difficult to capture in a single photograph. But this composite of telescopic images covers a wide range of exposure times to reveal the crown of the Sun in all its glory. The aligned and stacked digital frames were taken in clear skies above Stanley, Idaho in the Sawtooth Mountains during the Sun's total eclipse on August 21. A pinkish solar prominence extends just beyond the right edge of the solar disk. Even small details on the dark night side of the New Moon can be made out, illuminated by sunlight reflected from a Full Earth.

Image credit: Derek Demeter
The Eagle and The Swan (2017-08-24)

The Eagle Nebula and the Swan Nebula span this broad starscape, a telescopic view toward the Sagittarius spiral arm and the center of our Milky Way galaxy. The Eagle, also known as M16, is at top and M17, the Swan, at bottom of the frame showing the cosmic clouds as brighter regions of active star-formation. They lie along the spiral arm suffused with reddish emission charactistic of atomic hydrogen gas, and dusty dark nebulae. M17, also called the Omega Nebula, is about 5500 light-years away, while M16 is some 6500 light-years distant. The center of both nebulae are locations of well-known close-up images of star formation from the Hubble Space Telescope. In this mosaic image that extends about 3 degrees across the sky, narrowband, high-resultion image data has been used to enhance the central regions of the Eagle and Swan. The extended wings of the Eagle Nebula spread almost 120 light-years. The Swan is over 30 light-years across.

Image credit: Josep Drudis
Diamond Ring in a Cloudy Sky (2017-08-25)

As the Moon's shadow swept across the US on August 21, eclipse chasers in the narrow path of totality were treated to a diamond ring in the sky. At the beginning and end of totality, the fleeting and beautiful effect often produces audible gasps from an amazed audience. It occurs just before or after the appearance of the faint solar corona with a brief ring of light and glimpse of Sun. In this scene from the end of totality at Central, South Carolina, clouds drift near the Sun's diamond ring in the sky.

Image credit: Ashley Marando
Hurricane Harvey Strengthens (2017-08-26)

A large and dangerous hurricane has developed in the Gulf of Mexico.  The featured time-lapse video shows Hurricane Harvey growing to Category 4 strength over the past few days, as captured by NASA and NOAA's GOES-East satellite. Starting as a slight dip in air pressure, hurricanes swell into expansive spiraling storm systems, complete with high winds and driving rain.  Hurricanes are powered by evaporating ocean water, and so typically gain strength over warm water and lose strength over land.  Much remains unknown about hurricanes and cyclones, including details of how they are formed and the exact path they will take. Hurricane Harvey, accompanied by a dangerous storm surge, made landfall late yesterday in Texas.
The Heart Nebula in Hydrogen, Oxygen, and Sulfur (2017-08-27)

What powers the Heart Nebula?  The large emission nebula dubbed IC 1805 looks, in whole, like a heart.  The nebula's glow -- as well as the shape of the gas and dust clouds -- is powered by by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster Melotte 15. This deep telescopic image maps the pervasive light of narrow emission lines from atoms of hydrogen, oxygen, and sulfur in the nebula. The field of view spans just over two degrees on the sky, so that it appears larger than four times the diameter of a full moon. The cosmic heart is found in the constellation of Cassiopeia, the boastful mythical Queen of Aethiopia .

Image credit: Peter Jenkins
A Fleeting Double Eclipse of the Sun (2017-08-28)

Last week, for a fraction of a second, the Sun was eclipsed twice. One week ago today, many people in North America were treated to a standard, single, partial solar eclipse. Fewer people, all congregated along a narrow path, experienced the eerie daytime darkness of a total solar eclipse.  A dedicated few with fast enough camera equipment, however, were able to capture a double eclipse -- a simultaneous partial eclipse of the Sun by both the Moon and the International Space Station (ISS). The Earth-orbiting ISS crossed the Sun in less than a second, but to keep the ISS from appearing blurry, exposure times must be less than 1/1000th of a second. The featured image composite captured the ISS multiple times in succession as it zipped across the face of the Sun. The picture was taken from Huron, California in a specific color emitted by hydrogen which highlights the Sun's chromosphere, a layer hotter and higher up than the usually photographed photosphere.    Follow APOD on: Facebook,  Google Plus,  Instagram, or Twitter

Image credit: Simon Tang
Saturn in Blue and Gold (2017-08-29)

Why is Saturn partly blue?  The featured picture of Saturn approximates what a human would see if hovering close to the giant ringed world.   The image was taken in 2006 March by the robot Cassini spacecraft now orbiting Saturn.  Here Saturn's majestic rings appear directly only as a thin vertical line.  The rings show their complex structure in the dark shadows they create on the image left.   Saturn's fountain moon Enceladus, only about 500 kilometers across, is seen as the bump in the plane of the rings.  The northern hemisphere of Saturn can appear partly blue for the same reason that Earth's skies can appear blue -- molecules in the cloudless portions of both planet's atmospheres are better at scattering blue light than red.  When looking deep into Saturn's clouds, however, the natural gold hue of Saturn's clouds becomes dominant.   It is not known why southern Saturn does not show the same blue hue -- one hypothesis holds that clouds are higher there.   It is also not known why Saturn's clouds are colored gold. Next month, Cassini will end its mission with a final dramatic dive into Saturn's atmosphere.   Eclipses 2017: Memorable images submitted to APOD -- please "Like" your favorites.
Panoramic Eclipse Composite with Star Trails (2017-08-30)

What was happening in the sky during last week's total solar eclipse?  This featured little-planet, all-sky, double time-lapse, digitally-fused composite captured celestial action during both night and day from a single location. In this 360x180 panorama, north and south are at the image bottom and top, while east and west are at the left and right edges, respectively.  During four hours the night before the eclipse, star trails were captured circling the north celestial pole (bottom) as the Earth spun.  During the day of the total eclipse, the Sun was captured every fifteen minutes from sunrise to sunset (top), sometimes in partial eclipse. All of these images were then digitally merged onto a single image taken exactly during the total solar eclipse.  Then, the Sun's bright corona could be seen flaring around the dark new Moon (upper left), while Venus simultaneously became easily visible (top).  The tree in the middle, below the camera, is a Douglas fir. The images were taken with care and planning at  Magone Lake in Oregon, USA.   Total Eclipse 2017: More memorable images -- please "Like" your favorites.

Image credit: Nuits sacrees
Lunar View, Solar Eclipse (2017-08-31)

Swinging around the lunar nearside on August 21, the Lunar Reconnaissance Orbiter turned to look back on a bright, Full Earth. As anticipated its Narrow Angle Camera scanned this sharp view of our fair planet, catching the shadow of the Moon racing along a path across the United States at about 1,500 miles per hour. In fact, the dark lunar shadow is centered over Hopkinsville, Kentucky at 1:25:30pm Central Daylight Time.  From there, the New Moon blocked the Sun high in clear skies for about 2 minutes and 40 seconds in a total solar eclipse.
A First Glimpse of the Great American Eclipse (2017-09-01)

Making landfall in Oregon, the Moon's dark umbral shadow toured the United States on August 21. Those gathered along its coast to coast path were witness to a total eclipse of the Sun, possibly the most widely shared celestial event in history. But first, the Moon's shadow touched the northern Pacific and raced eastward toward land. This dramatic snapshot was taken while crossing the shadow path 250 miles off the Oregon coast, 45,000 feet above the cloudy northern Pacific. Though from a shorter totality, it captures the eclipse before it could be seen from the US mainland. With the eclipsed Sun not far above, beautiful colors appear along the eastern horizon giving way to a clear, pitch-black, stratospheric sky in the shadow of the Moon.

Image credit: Babak Tafreshi
Milky Way Voyager (2017-09-02)

Launched in 1977 on a tour of the outer planets of the Solar System, Voyager 1 and 2 have become the longest operating and most distant spacecraft from Earth. Nearly 16 light-hours from the Sun, Voyager 2 has reached the edge of the heliosphere, the realm defined by the influence of the solar wind and the Sun's magnetic field. Now humanity's first ambassador to the Milky Way, Voyager 1 is over 19 light-hours away, beyond the heliosphere in interstellar space. Celebrate the Voyagers' 40 year journey toward the stars with NASA on September 5.  Poster: Downloads
A Waterspout in Florida (2017-09-03)

What's happening over the water?  Pictured here is one of the better images yet recorded of a waterspout, a type of tornado that occurs over water.  Waterspouts are spinning columns of rising moist air that typically form over warm water. Waterspouts can be as dangerous as tornadoes and can feature wind speeds over 200 kilometers per hour.  Some waterspouts form away from thunderstorms and even during relatively fair weather.  Waterspouts may be relatively transparent and initially visible only by an unusual pattern they create on the water.  The featured image was taken in 2013 July near Tampa Bay, Florida. The Atlantic Ocean off the coast of Florida is arguably the most active area in the world for waterspouts, with hundreds forming each year.  Some people speculate that waterspouts are responsible for some of the losses recorded in the Bermuda Triangle.

Image credit: Joey Mole
Saturn's Rings from the Inside Out (2017-09-04)

What do Saturn's rings look like from Saturn? Images from the robotic spacecraft Cassini are providing humanity with this unprecedented vantage point as it nears the completion of its mission. Previous to Cassini's Grand Finale orbits, all images of Saturn's majestic ring system were taken from outside of the rings looking in.  Pictured in the inset is the remarkable video, while the spacecraft's positions are depicted in the surrounding animation.  Details of the complex rings are evident as the short time-lapse sequence begins, while the paper-thin thickness of the rings becomes apparent near the video's end. The featured images were taken on August 20. Cassini has only a few more orbits around Saturn left before it is directed to dive into the giant planet on September 15.
Europa and Jupiter from Voyager 1 (2017-09-05)

What are those spots on Jupiter? Largest and furthest, just right of center, is the Great Red Spot -- a huge storm system that has been raging on Jupiter possibly since Giovanni Cassini's likely notation of it 352 years ago.  It is not yet known why this Great Spot is red. The spot toward the lower left is one of Jupiter's largest moons: Europa. Images from Voyager in 1979 bolster the modern hypothesis that Europa has an underground ocean and is therefore a good place to look for extraterrestrial life. But what about the dark spot on the upper right? That is a shadow of another of Jupiter's large moons: Io. Voyager 1 discovered Io to be so volcanic that no impact craters could be found.  Sixteen frames from Voyager 1's flyby of Jupiter in 1979 were recently reprocessed and merged to create the featured image.  Forty years ago today, Voyager 1 launched from Earth and started one of the greatest explorations of the Solar System ever.    Free 40th Anniversary Downloads: Voyager Posters