juliensimon/nasa-apod huggingface dataset:
Meteor by Moonlight (2009-08-15)

Dark skies are favored for viewing meteor showers. But the annual Perseid Meteor Shower still entertained skygazers around the world this week even though the Moon brightened the night. At its last quarter phase and rising around midnight on August 13, after the shower's anticipated peak, the Moon is seen here above rock formations in the Alborz Mountains near Firouzkooh, Iran. With a dramatic desert landscape in the foreground, a Perseid meteor is streaking through the moonlit sky between the overexposed Moon and bright planet Jupiter at the upper right. A regular celestial event in the northern hemisphere, the Perseid Meteor Shower is caused by planet Earth's yearly passage through the dust stream cast off by comet Swift-Tuttle.

Image credit: Babak
Tafreshi
A Laser Strike at the Galactic Center (2009-08-16)

Why are these people shooting a powerful laser into the center of our Galaxy?  Fortunately, this is not meant to be the first step in a Galactic war.  Rather, astronomers at the Very Large Telescope (VLT) site in Chile are trying to measure the distortions of Earth's ever changing atmosphere.  Constant imaging of high-altitude atoms excited by the laser -- which appear like an artificial star -- allow astronomers to instantly measure atmospheric blurring.  This information is fed back to a VLT telescope mirror which is then slightly deformed to minimize this blurring.  In this case, a VLT was observing our Galaxy's center, and so Earth's atmospheric blurring in that direction was needed.  As for inter-galaxy warfare, when viewed from our Galaxy's center, no casualties are expected.  In fact, the light from this powerful laser would combine with light from our Sun to together appear only as bright as a faint and distant star.
Perseids from Perseus (2009-08-17)

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 last week's meteor shower was 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 image of this year's Pereids meteor shower shows many bright meteors that streaked through the sky on August 12.  To the surprise of many, the next night, August 13, also showed many meteors, as demonstrated by rolling one's cursor over the above image. This year's Leonids meteor shower in November is expected by some to be exceptionally active, perhaps producing as many as 500 meteors per hour.

Image credit: Chris Peterson
(Cloudbait Observatory)
The Milky Way Over the Badlands (2009-08-18)

Why take a picture of just the Badlands when you can take one that also shows the spectacular sky above it? Just such a picture, actually a digital stitched panorama of four images, was taken in late June near midnight, looking southwest. In the foreground, the unusual buttes of the Badlands Wall, part of the Badlands National Park in South Dakota, USA, were momentarily illuminated by flashlight during a long duration exposure of the background night sky. The mountain-like buttes visible are composed of soft rock that show sharp erosion features from wind and water. The South Dakota Badlands also contain ancient beds rich with easy-to-find fossils.  Some fossils are over 25 million years old and hold clues to the evolutionary origins of the horse and the saber-toothed tiger.  Bright Jupiter dominates the sky on the left just above the buttes, while the spectacular Milky Way Galaxy runs down the image right.

Image credit: Wally Pacholka
IC 1396 and Surrounding Starfield (2009-08-19)

Sprawling across hundreds of light-years, emission nebula IC 1396, visible on the upper right, mixes glowing cosmic gas and dark dust clouds. Stars are forming in this area, only about 3,000 light-years from Earth. This wide angle view also captures surrounding emission and absorption nebula.  The red glow in IC 1396 and across the image is created by cosmic hydrogen gas recapturing electrons knocked away by energetic starlight. The dark dust clouds are dense groups of smoke-like particles common in the disks of spiral galaxies. Among the intriguing dark shapes within IC 1396, the winding Elephant's Trunk nebula lies just right of the nebula's center. IC 1396 lies in the high and far off constellation of Cepheus.

Image credit: Thomas W. Earle
Eclipse City (2009-08-20)

During July 22nd's solar eclipse, the Moon's dark shadow traced a narrow path as it raced eastward across India and China and on into the Pacific. Hong Kong was south of the shadow's path, so a total eclipse was not visible there, but a partial eclipse was still enjoyed by inhabitants of the populous city. And while many were (safely!) watching the sky, images of the partially eclipsed Sun adorned the city itself. In this downlooking photo, taken at 9:40am local time, a remarkable array of solar eclipse views was created by reflection in a grid of eastward facing skyscraper windows. The photographer's location was the 27th floor of Two Pacific Place.

Image credit: Alfred Lee
The Whale and the Hockey Stick (2009-08-21)

NGC 4631 is a big beautiful spiral galaxy seen edge-on (top right) only 25 million light-years away towards the small northern constellation Canes Venatici. This galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others the popular moniker of The Whale Galaxy. Either way, it is similar in size to our own Milky Way. In this gorgeous color image, the Whale's dark interstellar dust clouds, yellowish core, and young blue star clusters are easy to spot. A companion galaxy, the small elliptical NGC 4627, appears above the Whale Galaxy. At the lower left is another distorted galaxy, the hockey stick-shaped NGC 4656. The distortions and mingling trails of gas detected at other wavelengths suggest that all three galaxies have had close encounters with each other in their past. The Whale Galaxy is also known to have spouted a halo of hot gas glowing in x-rays.

Image credit: Capella Observatory
The Gum Nebula (2009-08-22)

Named for Australian astronomer Colin Stanley Gum (1924-1960), The Gum Nebula is so large and close it is actually hard to see. In fact, we are only about 450 light-years from the front edge and 1,500 light-years from the back edge of this cosmic cloud of glowing hydrogen gas. Covered in this 41 degree-wide mosaic of H-alpha images, the faint emission region is otherwise easy to lose against the background of Milky Way stars. The complex nebula is thought to be a supernova remnant over a million years old, sprawling across the southern constellations Vela and Puppis.  Sliding your cursor over this spectacular wide field view will reveal the location of objects embedded in The Gum Nebula, including the Vela supernova remnant.

Image credit: Axel
Mellinger
Giant Cluster Bends, Breaks Images (2009-08-23)

What are those strange blue objects?  Many of the brightest blue images are of a single, unusual, beaded, blue, ring-like galaxy which just happens to line-up behind a giant cluster of galaxies.  Cluster galaxies here typically appear yellow and -- together with the cluster's dark matter -- act as a gravitational lens.  A gravitational lens can create several images of background galaxies, analogous to the many points of light one would see while looking through a wine glass at a distant street light.  The distinctive shape of this background galaxy -- which is probably just forming -- has allowed astronomers to deduce that it has separate images at 4, 10, 11, and 12  o'clock, from the center of the cluster.  A blue smudge near the cluster center is likely another image of the same background galaxy.  In all, a recent analysis postulated that at least 33 images of 11 separate background galaxies are discernable.  This spectacular photo of galaxy cluster CL0024+1654 from the Hubble Space Telescope was taken in November 2004.
Morning Glory Clouds Over Australia (2009-08-24)

What causes these long, strange clouds? No one is sure.  A rare type of cloud known as a Morning Glory cloud can stretch 1,000 kilometers long and occur at altitudes up to two kilometers high. Although similar roll clouds have been seen at specific places across the world, the ones over Burketown, Queensland Australia occur predictably every spring. Long, horizontal, circulating tubes of air might form when flowing, moist, cooling air encounters an inversion layer, an atmospheric layer where air temperature atypically increases with height.  These tubes and surrounding air could cause dangerous turbulence for airplanes when clear.  Morning Glory clouds can reportedly achieve an airspeed of 60 kilometers per hour over a surface with little discernible wind. Pictured above, photographer Mick Petroff photographed some Morning Glory clouds from his airplane near the Gulf of Carpentaria, Australia.
Equinox at Saturn (2009-08-25)

What would Saturn's rings look like if the ring plane pointed directly at the Sun? That situation occurred earlier this month when equinox occurred on Saturn.  Since the Earth is nearly in the same direction as the Sun from Saturn, the rings appeared to disappear from Earth. From the robotic Cassini spacecraft orbiting Saturn, however, the unusually illuminated ring plane could be viewed from on high. Pictured above, Saturn's rings, darker than ever seen before, were captured just a few hours before equinox on 2009 August 10. The reason for the unusual brightness of an inner ring is currently unknown, but possibly related to particle sizes there being larger than the 10 meter average thickness of the rest of Saturn's rings. Short light streaks in the frame are artificial image artifacts and have nothing to do with Saturn's ring plane. Planetary scientists will be studying ring images taken near equinox to help better understand the dynamics and particle size distribution of the Solar System's most extensive ring system.
Classic Orion Nebulae (2009-08-26)

The Great Nebula in Orion, also known as M42, is one of the most famous nebulae in the sky. The star forming region's glowing gas clouds and hot young stars are near the center of this colorful deep sky image that includes the smaller nebula M43 and dusty, bluish reflection nebulae NGC 1977 and friends on the left. Located at the edge of an otherwise invisible giant molecular cloud complex, these eye-catching nebulae represent only a small fraction of this galactic neighborhood's wealth of interstellar material. Captured with very modest equipment, the gorgeous skyscape was awarded Best in Show at the 2009 Starfest International Salon of Astrophotography. Judges commented that the detail and shading were exquisite in this version of a classic astronomical image. The field spans nearly 3 degrees or about 75 light-years at the Orion Nebula's estimated distance of 1,500 light-years.

Image credit: Kerry-Ann Lecky
Hepburn
A Dark Sky Over Sequoia National Park (2009-08-27)

Scroll right to take in the view from the highest summit in the contiguous USA. The above 360-degree digitally stitched panorama, taken in mid-July, shows the view from 4,400-meter high Mt. Whitney in Sequoia National Park, California. In the foreground, angular boulders populate Mt. Whitney's summit while in the distance, just below the horizon, peaks from the Sierra Nevada mountain range are visible. Sky sights include light pollution emanating from Los Angeles and Fresno, visible just above the horizon.  Dark clouds, particularly evident on the image left well above the horizon, are the remnants of a recent thunderstorm near Death Valley. High above, the band of the Milky Way Galaxy arches across the image left. Bright airglow bands are visible all over the sky but are particularly prominent on the image right.  The planet Jupiter appears as the brightest point on the image left. A discerning eye can also find a faint image of the far distant Andromeda galaxy, a satellite trail, and many constellations. Today marks the 100th anniversary of the completion of the historic stone shelter on Mt. Whitney, visible toward the image right.
NGC 7822 in Cepheus (2009-08-28)

Pillars of gas, dust, and young, hot stars fill the center of NGC 7822. At the edge of a giant molecular cloud toward the northern constellation Cepheus, the glowing star forming region lies about 3,000 light-years away. Within the nebula, bright edges and tantalizing shapes are highlighted in this colorful skyscape. The image includes data from both broadband and narrowband filters, mapping emission from atomic oxygen, hydrogen, and sulfur into blue, green, and red hues. The atomic emission is powered by the energetic radiation from the hot stars, whose powerful winds and radiation also sculpt and erode the denser pillar shapes. Stars could still be forming inside the pillars by gravitational collapse, but as the pillars are eroded away, any forming stars will ultimately be cutoff from their reservoir of star stuff. This field spans around 30 light-years at the estimated distance of NGC 7822.

Image credit: Don Goldman
NGC 7771 Galaxy Group (2009-08-29)

Slide your cursor over the image to identify three members of this intriguing gathering of galaxies.  Known as the NGC 7771 Group, they lie almost 200 million light-years away toward the high flying constellation Pegasus. The largest galaxy, barred spiral NGC 7771, is itself about 75,000 light-years across, but will someday find itself part of a larger galaxy still. As the galaxies of the group make repeated close passages, they will finally merge into one very large galaxy. Played out over hundreds of millions of years, the process is understood to be a normal part of the evolution of galaxies, including our own Milky Way.  Editor's Note: The labeled version of the image was generated by Astrometry.net.

Image credit: Kent Biggs
D. rad Bacteria: Candidate Astronauts (2009-08-30)

These bacteria could survive on another planet.  In an Earth lab, Deinococcus radiodurans (D. rad) survive extreme levels of radiation, extreme temperatures, dehydration, and exposure to genotoxic chemicals.  Amazingly, they even have the ability to repair their own DNA, usually within 48 hours.  Known as an extremophile, bacteria such as D. rad are of interest to NASA partly because they might be adaptable to help human astronauts survive on other worlds.  A recent map of D. rad's DNA might allow biologists to augment their survival skills with the ability to produce medicine, clean water, and oxygen.  Already they have been genetically engineered to help clean up spills of toxic mercury.  Likely one of the oldest surviving life forms, D. rad was discovered by accident in the 1950s when scientists investigating food preservation techniques could not easily kill it.  Pictured above, Deinococcus radiodurans grow quietly in a dish.
Open Cluster M25 (2009-08-31)

Many stars like our Sun were formed in open clusters. The above pictured open cluster, M25, contains thousands of stars and is about two thousand light years distant. The stars in this cluster all formed together about 90 million years ago. The bright young stars in M25 appear blue. Open clusters, also called galactic clusters, contain fewer and younger stars than globular clusters. Also unlike globular clusters, open clusters are generally confined to the plane of our Galaxy. M25 is visible with binoculars towards the constellation of the Archer ( Sagittarius).

Image credit: Jean-Charles Cuillandre
Shadows of Saturn at Equinox (2009-09-01)

Unusual shadows and dark rings appeared around Saturn near its equinox last month. At that time -- early August -- Saturn's ring plane pointed directly at the Sun. Visible above, Saturn's moon Tethys casts a shadow visible only on the far right. Saturn's own shadow blacks out a large swath of rings on the right. The night side of Saturn glows with ringshine -- sunlight reflected by ring particles back onto Saturn. Images near equinox at Saturn are giving astronomers a chance to search for unexpected shadows that may illuminate previously unknown features of Saturn's complex ring system.  Cassini, the robotic spacecraft orbiting Saturn that took this image, is not expected to survive to the next Saturnian equinox in 15 years.
Discovery's Rainbow (2009-09-02)

Just one minute before midnight EDT, Friday, August 28, the Space Shuttle Discovery began a long arc into a cloudy sky. Following the launch, a bright and remarkably colorful trail was captured in this time exposure from the Banana River Viewing Site, looking east toward pad 39A at the Kennedy Space Center. On STS-128, Discovery docked with the International Space Station Sunday evening. The 13-day mission will exchange space station crew members and deliver more than 7 tons of supplies and equipment. Of course, the equipment includes the Combined Operational Load Bearing External Resistance Treadmill (COLBERT).
Despina, Moon of Neptune (2009-09-03)

Despina is a tiny moon of Neptune. A mere 148 kilometers across, diminutive Despina was discovered in 1989, in images from the Voyager 2 spacecraft taken during its encounter with the solar system's most distant gas giant planet. But looking through the Voyager 2 data 20 years later, amateur image processor (and philosophy professor) Ted Stryk discovered something no one had recognized before -- images that show the shadow of Despina in transit across Neptune's blue cloud tops. His composite view of Despina and its shadow is composed of four archival frames taken on August 24, 1989, separated by nine minutes. Despina itself has been artificially brightened to make it easier to see. In ancient Greek mythology, Despina is a daughter of Poseidon (the Roman god Neptune).
6 Years of Saturn (2009-09-04)

Today, planet Earth passes through the plane of Saturn's rings. From the perspective of earthbound astronomers, Saturn's rings will be edge-on. The problem is, Saturn itself is now very close to the Sun, low on horizon after sunset, so good telescopic images will be difficult to come by. Still, this composite of Saturn views taken from 2004 - 2009 (lower right to upper left) illustrates the change in ring tilt over the last six years and includes a nearly edge-on ring view, based on images captured earlier this year. While Saturn's south pole is clearly seen in the sequence, particularly at the lower right, it will be hidden in the coming years. Saturn's north pole will be increasingly visible, along with the tilting rings, as the planet emerges this fall in the predawn sky.

Image credit: Alan Friedman
Supernova Remnant E0102-72 (2009-09-05)

The expanding debris cloud from the explosion of a massive star is captured in this multiwavelength composite, combining x-ray and optical images from the Chandra and Hubble telescopes. Identified as E0102-72, the supernova remnant lies about 190,000 light-years away in our neighboring galaxy, the Small Magellanic Cloud. A strong cosmic source of x-rays, E0102 was imaged by the Chandra X-ray Observatory shortly after its launch in 1999. In celebration of Chandra's 10th anniversary, this colorful view of E0102 and its environs was created, including additional Chandra data. An analysis of all the data indicates that the overall shape of E0102 is most likely a cylinder that is viewed end-on rather than a spherical bubble. The intriguing result implies that the massive star's explosion has produced a shape similar to what is seen in some planetary nebulae associated with lower mass stars. At the distance of the Small Magellanic Cloud, this field of view spans about 150 light-years.
CMBR Dipole: Speeding Through the Universe (2009-09-06)

Our Earth is not at rest.  The Earth moves around the Sun.  The Sun orbits the center of the Milky Way Galaxy.  The Milky Way Galaxy orbits in the Local Group of Galaxies.  The Local Group falls toward the Virgo Cluster of Galaxies.  But these speeds are less than the speed that all of these objects together move relative to the cosmic microwave background radiation (CMBR).  In the above all-sky map from the COBE satellite, radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and colder.  The map indicates that the Local Group moves at about 600 kilometers per second relative to this primordial radiation.  This high speed was initially unexpected and its magnitude is still unexplained.  Why are we moving so fast?  What is out there?
Jupiter Over the Mediterranean (2009-09-07)

This vacation included a sight to remember. Pictured above, a picturesque starscape capped a serene seascape as seen from Turkey this past August.  In the above digitally stitched panorama, the Gelidonya Lighthouse shines in the foreground before a calm Mediterranean Sea. On the left, Jupiter is the brightest point in the image and since on the same side of the Sun as the Earth, was near its yearly brightest.  Glowing just shy of magnitude -3, Jupiter was brighter than any star in the sky, and brighter even than Mars was during its famously bright opposition of 2003 August. On the right, the band of the Milky Way Galaxy fades into distant atmospheric haze above the horizon. Jupiter is nearing the closest part of its elliptical orbit to the Sun and so will appear even brighter during its next opposition in 2010 September.

Image credit: Tunç Tezel
Unexpected Impact on Jupiter (2009-09-08)

Two months ago, something unexpected hit Jupiter. First discovered by an amateur astronomer Anthony Wesley on 2009 July 19, the impact was quickly confirmed and even imaged by the Hubble Space Telescope during the next week. Many of the world's telescopes then zoomed in on our Solar System's largest planet to see the result. Some of these images have been complied into the above animation. Over the course of the last month and a half, the above time-lapse sequence shows the dark spot -- first created when Jupiter was struck -- deforming and dissipating as Jupiter's clouds churned and Jupiter rotated.  It is now thought that a small comet -- perhaps less than one kilometer across -- impacted Jupiter on or before 2009 July 19. Although initially expected to be visible for only a week, astronomers continue to track atmospheric remnants of the impact for new information about winds and currents in Jupiter's thick atmosphere.
Star Trails Over Oregon (2009-09-09)

As the Earth spins on its axis, the sky seems to rotate around us. This motion, called diurnal motion, produces the beautiful concentric trails traced by stars during time exposures.  Partial-circle star trails are pictured above over Grants Pass, Oregon, USA last month. Near the middle of the circles is the North Celestial Pole (NCP), easily identified as the point in the sky at the center of all the star trail arcs. The star Polaris, commonly known as the North Star, made the very short bright circle near the NCP.  About 12,000 years ago, the bright star Vega was the North Star, and in about 14,000 years, as the Earth's spin axis slowly continues to precess, Vega will become the North Star again.

Image credit: Joshua Bury
The Butterfly Nebula from Upgraded Hubble (2009-09-10)

The bright clusters and nebulae of planet Earth's night sky are often named for flowers or insects, and NGC 6302 is no exception. With an estimated surface temperature of about 250,000 degrees C, the central star of this particular planetary nebula is exceptionally hot though -- shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust.  This dramatically detailed close-up of the dying star's nebula was recorded by the newly upgraded Hubble Space Telescope. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is near the center of this view, almost edge-on to the line-of-sight. Molecular hydrogen has been detected in the hot star's dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically correct constellation Scorpius.