juliensimon/nasa-apod huggingface dataset:
The Little Dipper (2011-05-14)

At 2nd magnitude, Polaris is far from the brightest star in the night sky. But it is the brightest star at the left of this well-composed, starry mosaic spanning about 23 degrees across the northern sky asterism dubbed the Little Dipper. Polaris is famous as the North Pole Star, a friend to navigators and astrophotographers alike, but it's not located exactly at the North Celestial Pole (NCP) either. It's presently offset from the NCP by 0.7 degrees. Sliding your cursor over the picture will locate Polaris and the NCP as well as other stars of the Little Dipper. The stars are shown with their proper names preceded by their greek alphabet designations within the ancient constellation Ursa Minor, the Little Bear. Dust clouds suspended above the plane of our Milky Way Galaxy are also faintly visible throughout the wide field of view.

Image credit: Rogelio
Bernal Andreo
The Sombrero Galaxy from Hubble (2011-05-15)

What's going on in the center of this spiral galaxy? Named the Sombrero Galaxy for its hat-like resemblance, M104 features a prominent dust lane and a bright halo of stars and globular clusters. Reasons for the Sombrero's hat-like appearance include an unusually large and extended central bulge of stars, and dark prominent dust lanes that appear in a disk that we see nearly edge-on. Billions of old stars cause the diffuse glow of the extended central bulge.  Close inspection of the bulge in the above photograph shows many points of light that are actually globular clusters. M104's spectacular dust rings harbor many younger and brighter stars, and show intricate details astronomers don't yet fully understand.  The very center of the Sombrero glows across the electromagnetic spectrum, and is thought to house a large black hole.  Fifty million-year-old light from the Sombrero Galaxy can be seen with a small telescope towards the constellation of Virgo.
Time Lapse Clouds and Sky Over the Canary Islands (2011-05-16)

If you could sit back and watch clouds and the sky move all night and day, what might you see? One answer from the island of Tenerife, captured over the course of the year, includes sequences that are not only breathtaking but instructive.  Visible in the above time-lapse movie include clouds that seem to flow like water, a setting sun that shows numerous green flashes, the Milky Way Galaxy rising behind towering plants, a colorful double fogbow, lenticular clouds that appear stationary near their mountain peaks, and colorful moon coronas.  The above video was shot solely from the Teide National Park on Tenerife in the Canary Islands of Spain, off the north west coast of Africa.  The video also features an unusual type of plant in several scenes -- can you identify it?

Image credit: Daniel López
A Starry Night of Iceland (2011-05-17)

On some nights, the sky is the best show in town. On this night, the sky was not only the best show in town, but a composite image of the sky won an international competition for landscape astrophotography. The above winning image was taken two months ago over J�kuls�rl�n, the largest glacial lake in Iceland.  The photographer combined six exposures to capture not only two green auroral rings, but their reflections off the serene lake. Visible in the distant background sky is the band of our Milky Way Galaxy, the Pleiades open clusters of stars, and the Andromeda galaxy. A powerful coronal mass ejection from the Sun caused auroras to be seen as far south as Wisconsin, USA. As the Sun progresses toward solar maximum in the next few years, many more spectacular images of aurora are expected.
The Last Launch of Space Shuttle Endeavour (2011-05-18)

Two days ago, powerful yet controlled explosions rocketed the Space Shuttle Endeavour on its final trip into Earth orbit. The above image was taken seconds after liftoff as the massive orbiter and six astronauts began a climb to a height where the atmosphere is so thin it is unbreathable. The shuttle, on mission STS-134, is expected to dock with the International Space Station (ISS) today. The Endeavour will deliver to the ISS, among other things, an ambitious detector called the Alpha Magnetic Spectrometer 2 (AMS), a detector that over the next few years could detect a significant abundance of specific types of dark matter, charged antimatter, and even a strangely possible variation of familiar matter called strangelets.  The very last trip for any space shuttle is currently planned for mid-July when Atlantis will also visit the space station.
NGC 253: Close Up (2011-05-19)

This dusty island universe is one of the brightest spiral galaxies in planet Earth's sky. Seen nearly edge-on, NGC 253 is only 13 million light-years away, the largest member of the Sculptor Group of galaxies, neighbor to our own local galaxy group. The detailed close-up view is a five frame mosaic based on data assembled from the Hubble Legacy Archive.  Beginning on the left near the galaxy's core, the sharp panorama follows dusty filaments, interstellar gas clouds, and even individual stars toward the galaxy's edge at the right. The magnificent vista spans nearly 50,000 light-years. The frame at the far right has been compressed slightly to bring into view an intriguing pair of background galaxies. Designated a starburst galaxy because of its frantic star forming activity, NGC 253 features tendrils of dust rising from a galactic disk laced with young star clusters and star forming regions. NGC 253 is also known to be a strong source of high-energy x-rays and gamma rays, likely due to massive black holes near the galaxy's center.
A Journey Through the Night Sky (2011-05-20)

Majestic nebulae and stars of our Milky Way Galaxy stretch across this panoramic image of the entire night sky. At full resolution, the 5 gigapixel mosaic was stitched together from over 37,000 images, the result of a season following, year long effort and 60,000 travel miles in search of still dark skies in the American west and the western Cape of South Africa. The well-planned project combined many exposures from the dark sites, intended to produce an inspiring view of the night to rival the brightness of day. An interactive journey through the scene will uncover a congeries of innumerable stars with vast clouds of gas and dust strewn along the galactic plane and central bulge, too faint to see with the unaided eye. Even galaxies of stars beyond our Milky Way can be found within the cosmic vista.

Image credit: Photopic Sky Survey
Planets, Endeavour at Dawn (2011-05-21)

When dawn broke over Kennedy Space Center on Monday, May 16, the space shuttle orbiter Endeavour still stood on pad 39A. Its final launch, on mission STS-134 to the International Space Station, was only hours away. Shining through the early morning twilight four planets were also poised above the eastern horizon, a moving scene captured here from across the Banana River at the center's Saturn V VIP viewing site. Scattered by planet Earth's dense atmosphere, floodlight beams play over the launch pad, glancing skyward toward the celestial beacons. Jupiter is highest, near the top of the frame, but even the solar sytem's ruling gas giant is outshone by brilliant Venus near picture center. Innermost planet Mercury is below Venus, to the right. Below and left, Mars almost fades into the twilight glow. The four planets continue to hug the eastern horizon at dawn throughout the month, while Endeavour is now scheduled to make its final approach to planet Earth on June 1.

Image credit: Daniel Herron
Io: The Prometheus Plume (2011-05-22)

What's happening on Jupiter's moon Io? Two sulfurous eruptions are visible on Jupiter's volcanic moon Io in this color composite image from the robotic Galileo spacecraft that orbited Jupiter from 1995 to 2003. At the image top, over Io's limb, a bluish plume rises about 140 kilometers above the surface of a volcanic caldera known as Pillan Patera. In the image middle, near the night/day shadow line, the ring shaped Prometheus plume is seen rising about 75 kilometers above Io while casting a shadow below the volcanic vent. Named for the Greek god who gave mortals fire, the Prometheus plume is visible in every image ever made of the region dating back to the Voyager flybys of 1979 - presenting the possibility that this plume has been continuously active for at least 18 years. The above digitally sharpened image of Io was originally recorded in 1997 from a distance of about 600,000 kilometers. Recent analyses of Galileo data has uncovered evidence of a magma ocean beneath Io's surface.
An Unexpected Flare from the Crab Nebula (2011-05-23)

Why does the Crab Nebula flare? No one is sure. The unusual behavior, discovered over the past few years, seems only to occur in very high energy light -- gamma rays. As recently as one month ago, gamma-ray observations of the Crab Nebula by the Fermi Gamma Ray Space Telescope showed an unexpected increase in gamma-ray brightness, becoming about five times the nebula's usual gamma-ray brightness, and fading again in only a few days. Now usually the faster the variability, the smaller the region involved. This might indicate that the powerful pulsar at the center of the Crab, a compact neutron star rotating 30 times a second, is somehow involved. Specifically, speculation is centered on the changing magnetic field that surely surrounds the powerful pulsar.  Rapid changes in this field might lead to waves of rapidly accelerated electrons which emit the flares, possibly in ways similar to our Sun. The above image shows how the Crab Nebula normally appears in gamma rays, as compared to the Geminga pulsar, and how it then appeared during the recent brightening.
Three Arches Above Utah (2011-05-24)

How many arches can you count in the above image? If you count both spans of the Double Arch in the Arches National Park in Utah, USA, then two.  But since the above image was taken during a clear dark night, it caught a photogenic third arch far in the distance -- that of the overreaching Milky Way Galaxy. Because we are situated in the midst of the spiral Milky Way Galaxy, the band of the central disk appears all around us. The sandstone arches of the Double Arch were formed from the erosion of falling water. The larger arch rises over 30 meters above the surrounding salt bed and spans close to 50 meters across.  The dark silhouettes across the image bottom are sandstone monoliths left over from silt-filled crevices in an evaporated 300 million year old salty sea.  A dim flow created by light pollution from Moab, Utah can also be seen in the distance.

Image credit: Brad Goldpaint  
(Goldpaint Photography)
Space Shuttle Rising (2011-05-25)

What's that rising from the clouds?  The space shuttle. If you looked out the window of an airplane at just the right place and time last week, you could have seen something very unusual -- the space shuttle Endeavour launching to orbit.  Images of the rising shuttle and its plume became widely circulated over the web shortly after Endeavour's final launch. The above image was taken from a shuttle training aircraft and is not copyrighted. Taken well above the clouds, the image can be matched with similar images of the same shuttle plume taken below the clouds.  Hot glowing gasses expelled by the engines are visible near the rising shuttle, as well as a long smoke plume.  A shadow of the plume appears on the cloud deck, indicating the direction of the Sun. The shuttle Endeavour remains docked with the International Space Station and is currently scheduled to return to Earth next week.
Supernova Sonata (2011-05-26)

To create a sonata from supernovae, first you have to find the supernovae. To do that composers Alex Parker and Melissa Graham relied on the Canada France Hawaii Telescope (CFHT) Legacy Survey data of four deep fields on the sky monitored from April 2003 through August 2006, adopting 241 Type Ia supernovae. Enchanting to cosmologists, Type Ia supernovae are thermonuclear explosions that destroy white dwarf stars. Then, they gave each supernova a note to play, the volume of the note determined by the distance to the supernova. Fainter, more distant supernovae play quieter notes. Each note's pitch was based on a stretch factor measured by how fast the supernova brightens and fades over time relative to a standard time history. Higher stretch factors play higher notes in pitches drawn from the illustrated Phrygian dominant scale. Of course, each supernova note is played on an instrument. Supernovae in massive galaxies were assigned to a stand-up bass, while supernovae in less massive galaxies played their note on a grand piano. Click on the image or follow these links (Vimeo, YouTube) to watch a time compressed animation of the CFHT Legacy Survey data while listening to the Supernova Sonata.
Messier Marathon (2011-05-27)

In this action scene, red night vision lights, green laser pointers, tripods and telescopes in faint silhouette surround intrepid sky gazers embarked on the 10th annual Iran Messier Marathon. Completing the marathon requires viewing all 110 objects in 18th century French astronomer Charles Messier's catalog in one glorious dusk-to-dawn observing run. As daunting as it sounds, there are often favorable weekend dates for northern hemisphere marathoners to complete the task that fall on nearly moonless nights near the spring equinox. With the Milky Way as a backdrop, this group of about 150 astronomy enthusiasts conducted their 2011 marathon on such a night in April from the desert area of Seh Qaleh, in eastern Iran. Placing your cursor over the image will map the stunning night sky above their remote and very dark observing site. Follow the green laser pointer toward the Messier catalog objects (for example, M8) near the galactic center. Astronomer and former Messier Marathon organizer Babak Tafreshi also composed Sky Gazers, a time-lapse movie of this year's event.

Image credit: Babak Tafreshi
The Mileage of Light (2011-05-28)

If you're driving down a dark road on a starry night, you might want to check the odometer. Earlier this month, when traveling astronomer Dennis Mammana did he was greeted with the significant mileage reading of 186,282 miles. That's the number of miles light travels in one second. Or, if you prefer kilometers, the number you are looking for is 299,792. Mammana muses that in driving to countless observatories, star parties, and night sky photo shoots it has taken his 1998 vintage sport utility vehicle over 13 years to cover that distance. Of course, he considers his next important mileage milestone to be the distance to the Moon.

Image credit: Dennis L. Mammana
(TWAN)
Comet Between Fireworks and Lightning (2011-05-29)

Sometimes the sky itself is the best show in town.  In January 2007, people from Perth, Australia gathered on a local beach to watch a sky light up with delights near and far.  Nearby, fireworks exploded as part of Australia Day celebrations.  On the far right, lightning from a thunderstorm flashed in the distance.  Near the image center, though, seen through clouds, was the most unusual sight of all: Comet McNaught.  The photogenic comet was so bright that it even remained visible though the din of Earthly flashes.  Comet McNaught has now returned to the outer Solar System and is now only visible with a large telescope. The above image is actually a three photograph panorama digitally processed to reduce red reflections from the exploding firework.

Image credit: Antti Kemppainen
Last Panorama of the Spirit Rover on Mars (2011-05-30)

This is the last thing that the Spirit rover on Mars ever saw. Operating years beyond original expectations, Spirit eventually got mired in martian dirt and then ran out of power when investigating the unusual Home Plate surface feature on Mars. Visible in the above panorama are numerous rocks and slopes of the surrounding Columbia Hills of Mars.  The strange hill with the light colored top, visible near the top center of the image, has been dubbed von Braun and was a future destination when Spirit got bogged down. A leading hypothesis holds that von Braun is related to martian volcanism. Last week, NASA stopped trying to contact Spirit after numerous attempts. Half a world away, Spirit's sister rover Opportunity continues to roll toward Endeavour Crater, which could become the largest crater yet visited by an earthling-created robot.
Jets from Unusual Galaxy Centaurus A (2011-05-31)

Jets of streaming plasma expelled by the central black hole of a massive spiral galaxy  light up this composite image of Centaurus A. The jets emanating from Cen A are over a million light years long. Exactly how the central black hole expels infalling matter is still unknown. After clearing the galaxy, however, the jets inflate large radio bubbles that likely glow for millions of years. If excited by a passing front, radio bubbles can even light up again after a billion years. X-ray light is depicted in the above composite image in blue, while microwave light is false-colored orange.  The inset image in radio light shows newly imaged, never seen-before details of the innermost light year of the central jet.
Earth Rotating Under Very Large Telescopes (2011-06-01)

Why is the Earth moving in the above video? Most time lapse videos of the night sky show the stars and sky moving above a steady Earth. Here, however, the frames have been digitally rotated so that it is the stars that stay (approximately) steady, and the Earth that moves beneath them. The video dramatically shows the actual rotation of the Earth, called diurnal motion, in a clear and moving way, as if the camera were floating free in space.  The telescopes featured in the video are the Very Large Telescopes (VLT) in Chile, a group of four of the largest optical telescopes deployed anywhere in the world. A discerning observer of the above time lapse movie may also note the use of laser guide stars, zodiacal light, the Large and Small Magellanic Clouds, and fast-moving, sunlight-reflecting, Earth-orbiting satellites. The original video, on which the above sequences are based, can be found here.
Endeavour's Starry Night (2011-06-02)

This luminous night view of the space shuttle orbiter Endeavour, docked with the International Space Station for a final time, was captured on May 28. Orbiting 350 kilometers above planet Earth, Endeavour's payload bay is lit up as it hurtles through Earth's shadow at 17,000 miles per hour. At the top of the frame, the jointed appendages of the station's robotic manipulator arm Dextre appear in silhouette. Motion during the long exposure produced streaks in the starry background and the city lights on the darkened planet below. Completing a 16 day mission, Endeavour made a final landing at Kennedy Space Center in the dark, early morning hours of June 1.
Midnight's Solar Eclipse (2011-06-03)

On June 1, the shadow of the New Moon was cast across a land of the midnight Sun in this year's second partial solar eclipse. This picture of the geocentric celestial event above the Arctic Circle was taken near midnight from northern Finland's Kaunispää Hill in Lapland. Of course the region's reindeer were able to watch as both Moon and Sun hugged the northern horizon just above a cloud bank. Also visible from parts of Alaska and Canada, the eclipse began at sunrise in Siberia and northern China at 19:25 UT, ending about 3.5 hours later north of Newfoundland in the Atlantic Ocean. Remarkably, just one lunation later, on July 1 the New Moon's shadow will again reach out and touch the Earth in a partial solar eclipse, limited in visibility to a relatively small area in the Antarctic Ocean. July's eclipse will be followed by the fourth and final partial solar eclipse of 2011 on November 25. That eclipse will be seen from a southern land of the midnight Sun.

Image credit: Catalin Beldea
Dawn's Grand Finale (2011-06-04)

After more than a month, the lovely lineup of four naked-eye planets in dawn skies is coming to a close. Still, on May 31st a slender Moon joined the grouping along the eastern horizon for a final celestial performance, presented in this early morning scene from a beach near Buenos Aires, Argentina. A favorable view of the configuration in the southern hemisphere autumn, the photo was taken about 30 minutes before sunrise. In order from bottom to top, wandering Mercury, Venus, Mars, and Jupiter are stretched along the ecliptic plane. The Moon's sunlit crescent is sinking into the colorful twilight glow just left of Mercury. In dawns to come, Mars and Jupiter will continue to rise while Venus and Mercury sink toward the horizon, drawing closer to the rising Sun.

Image credit: Luis Argerich
Another Nearby Supernova in the Whirlpool Galaxy (2011-06-05)

One of the brightest supernovas in recent years has just been recorded in the nearby Whirlpool galaxy (M51). Surprisingly, a seemingly similar supernova was recorded in M51 during 2005, following yet another one that occurred in 1994. Three supernovas in 17 years is a lot for single galaxy, and reasons for the supernova surge in M51 are being debated. Pictured above are two images of M51 taken with a small telescope: one taken on May 30 that does not show the supernova, and one taken on June 2 which does. The June 2 image is one of the first images reported to contain the supernova.  The images are blinked to show the location of the exploded star. Although most supernovas follow classic brightness patterns, the precise brightening and dimming pattern of this or any supernova is hard to predict in advance and can tell astronomers much about what is happening.  Currently, the M51 supernova, designated SN 2011dh, is still bright enough to follow with a small telescope. Therefore, sky enthusiasts are encouraged to image the Whirlpool galaxy as often as possible to fill in time gaps left by intermittent observations made by the world's most powerful telescopes. Views of the developing supernova are being uploaded here.

Image credit: Stephane Lamotte Bailey,
Marc Deldem, &
Jean-Luc Dauvergne
Geometer's Playground Over Wyoming (2011-06-06)

If you travel several kilometers off a main highway through Wyoming, you may see an unusual sight. In particular, near Buford, Wyoming, USA, you could run across the geometric Ames Monument, visible on the right, built to commemorate the financiers of a historic transcontinental railroad across North America.  The above spectacular wide field mosaic, however, has also captured other geometric designs, many of them far in the distance. On the far left, for example, is a lunar halo surrounding by a lunar corona surrounding the setting Moon.  On the right, however, is the arch of the central band of our Milky Way Galaxy surrounding the pyramidal structure.  Illuminating the horizon to the right of the monument are the city lights of Cheyenne. The menagerie of images used to create this 360-degree composite were all taken during a single night last month.  Still, the digital stitching of images taken over such a long period of time has led to a few unnatural land and sky justapositions.  Can you identify any?

Image credit: Robert Arn
A Last Landing for Space Shuttle Endeavour (2011-06-07)

Space shuttle Endeavour is home to stay. In a rare night landing last week, Endeavour glided onto a runway in Cape Canaveral, Florida, USA completing a 16-day mission that included a visit to the International Space Station (ISS). All told, space shuttle Endeavour flew 25 flights since being deployed by NASA in 1992, spending a total of 299 days in space. Endeavour's next mission will be a stationary one in the California Science Center.  Even as Endeavour was landing, the space shuttle Atlantis was being rolled out in preparation for the last mission of any Space Shuttle, a mission currently scheduled to begin on July 8.