omnianasa/nasa-apod-metadata huggingface dataset:
Lewin's Challenge: 360 Degree Star Trails (2011-07-17)
You could be the first person ever to take a real single-exposure image like this. The above image from Vienna, Austria is not real in the sense that the 360 degree star trails in the sky appear only because of a digital trick. Real star trails observed above Vienna could never go 360 degrees around because the Sun would rise at some time during the exposure and dominate the frame. Star trails of any length occur because as the Earth spins on its axis, the sky seems to rotate around us.  This motion, called diurnal motion, produces the beautiful concentric arcs traced by stars during long time exposures.  Towards the middle of the above digitally stretched picture 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.  Walter Lewin, though, has asked APOD to pose this as a challenge to astrophotographers: create a real single-exposure image of a clear night sky that features 360 degree star trails.  Of course, such an image would only be possible near the poles of our fair planet, because only there could a nighttime run for more than 24 hours.
A Busy Space Walk at the Space Station (2011-07-18)
What's that astronaut doing? Unloading a space shuttle -- for the last time. After the space shuttle Atlantis docked with the International Space Station (ISS) last week, astronaut Mike Fossum underwent a long spacewalk that included carrying a Robotics Refueling Mission (RRM) payload from Atlantis' cargo bay to a platform used by the space station's famous robot DEXTRE. On Earth, the RRM box would have the weight of about three people and be much more difficult to carry. Pictured above on the far left, DEXTRE prepares to help move a failed space pump back to Atlantis. Visible behind the astronaut is the space station's Kibo Experimental Module.  The much awaited  final shuttle return flight is currently scheduled for 5:56 am EDT Thursday, July 21.   Quiz: How many national flags appear, at least in part, in the above image?
Vesta Vista (2011-07-19)
What does the surface of asteroid Vesta look like? The brightest asteroid in the Solar System and the object which takes up about 10 percent of the entire mass of the main asteroid belt had never been seen up close before. Over the past few weeks, however, the robotic Dawn spacecraft became the first spacecraft ever to approach Vesta. A few days ago, just after attaining orbit, Dawn took the above image. Early images show Vesta to be an old and battered world, covered with craters, bulges, grooves, and cliffs. Studying Vesta may give clues to the formative years of our early Solar System, as the unusual world may be one of the largest remaining protoplanets. After a year of studying Vesta, Dawn is scheduled to leave orbit and, in 2015, approach the only asteroid-belt object that is larger: Ceres.   Poll: Which of these recently submitted images would make good future APODs?
Noctilucent Clouds Over Edmonton (2011-07-20)
Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun, sunset rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on clouds above.  Under usual circumstances, a pretty sunset might be visible, but unusual noctilucent clouds float so high up they can be seen well after dark.  Normally too dim to be seen, they may become visible at sunset during late summer when illuminated by sunlight from below.  Noctilucent clouds are the highest clouds known and thought to be part of polar mesospheric clouds.  Pictured above earlier this month, a network of noctilucent clouds cast an eerie white glow after dusk, above the the city of Edmonton, in Alberta, Canada.  Much about noctilucent clouds has been discovered only over the past few years, while how they form and evolve remains a topic of active research.
Atlantis Farewell from Parkes (2011-07-21)
The Parkes 64 meter radio telescope is known for its contribution to human spaceflight, famously supplying television images from the Moon to denizens of planet Earth during Apollo 11. The enormous, steerable, single dish looms in the foreground of this early evening skyscape. Above it, the starry skies of New South Wales, Australia include familiar southerly constellations Vela, Puppis, and Hydra along with a sight that will never be seen again. Still glinting in sunlight and streaking right to left just below the radio telescope's focus cabin, the space shuttle orbiter Atlantis has just undocked with the International Space Station for the final time. The space station itself follows arcing from the lower right corner of the frame, about two minutes behind Atlantis in low Earth orbit. Atlantis made its final landing early this morning (July 21, 5:57am EDT) at NASA's Kennedy Space Center.
Pluto's P4 (2011-07-22)
Nix and Hydra were first introduced to human eyes in Hubble Space Telescope images from May 2005, as Pluto's second and third known moons. Now Hubble images have revealed a fourth satellite for the icy, dwarf planet. Provisionally designated P4, it completes an orbit of Pluto in about 31 days. Presently Pluto's smallest and dimmest known moon, P4 is estimated to be 13 to 34 kilometers across.  The newly discovered satellite was first spotted in Hubble observations from June 28, and later confirmed in a follow-up on July 3 and July 18. These two panels are composites of both the short and long exposures that include brighter Pluto itself along with Pluto's largest moon Charon. Camera noise and image artifacts also show up in the long exposure segments. The Hubble observations were made while searching for faint rings around the distant world in support of NASA's New Horizons mission, set to fly by the Pluto system in 2015.
NGC 2403 in Camelopardalis (2011-07-23)
Magnificent island universe NGC 2403 stands within the boundaries of the long-necked constellation Camelopardalis. Some 10 million light-years distant and about 50,000 light-years across, the spiral galaxy also seems to have more than its fair share of giant star forming HII regions, marked by the telltale reddish glow of atomic hydrogen gas. In fact, NGC 2403 closely resembles another galaxy with an abundance of star forming regions that lies within our own local galaxy group, M33 the Triangulum Galaxy. Of course, supernova explosions follow close on the heels of the formation of massive, short-lived stars and in 2004 one of the brightest supernovae discovered in recent times was found in NGC 2403. Easy to confuse with a foreground star in our own Milky Way Galaxy, the powerful supernova is seen here as the spiky, bright "star" at the left edge of the field. This stunning cosmic portrait is a composite of space and ground-based image data from the Hubble Legacy Archive and the 8.2 meter Subaru Telescope at the summit of Mauna Kea, Hawaii.
A Flight of Helios (2011-07-24)
An example of solar-powered flight, NASA's Helios aircraft flew almost one hundred years after the Wright brothers' historic flight on December 17, 1903. Pictured here at 3,000 meters in in skies northwest of Kauai, Hawaii, USA in August 2001, the remotely piloted Helios is traveling at about 40 kilometers per hour. Essentially an ultralight flying wing with 14 electric motors, the aircraft was built by AeroVironment Inc. Covered with solar cells, Helios' impressive 247 foot wide wing exceeded the wing span and even overall length of a Boeing 747 jet airliner. Climbing during daylight hours, the prototype aircraft ultimately reached an altitude just short of 30,000 meters, breaking records for non-rocket powered flight. Helios was intended as a technology demonstrator, but in the extremely thin air 30,000 meters above Earth's surface, the flight of Helios also approached conditions for winged flight in the atmosphere of Mars.
Milky Way Over Abandoned Kilns (2011-07-25)
What's that below the Milky Way? Historic kilns. Built in the 1870s in rural Nevada, USA to process local wood into charcoal, the kilns were soon abandoned due to a town fire and flooding, but remain in good condition even today. The above panorama is a digital conglomerate of five separate images taken in early June from the same location.  Visible above the unusual kilns is a colorful star field, highlighted by the central band of our Milky Way Galaxy appearing along a diagonal toward the lower right.  Many famous sites in our Galaxy are visible, including the Pipe Nebula and the Dark River to Antares, seen to the right of the Milky Way. The origin of the green mist on the lower left, however, is currently unexplained.
Galaxy NGC 474: Cosmic Blender (2011-07-26)
What's happening to galaxy NGC 474? The multiple layers of emission appear strangely complex and unexpected given the relatively featureless appearance of the elliptical galaxy in less deep images. The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively the shells may be like ripples in a pond, where the ongoing collision with the spiral galaxy just above NGC 474 is causing density waves to ripple though the galactic giant. Regardless of the actual cause, the above image dramatically highlights the increasing consensus that at least some elliptical galaxies have formed in the recent past, and that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with -- and accretions of -- smaller nearby galaxies. The halo of our own Milky Way Galaxy is one example of such unexpected complexity. NGC 474 spans about 250,000 light years and lies about 100 million light years distant toward the constellation of the Fish (Pisces).   APOD Lecture and Star Party: This Friday night at Ft. Wilkins, Michigan
Introducing Comet Garradd (2011-07-27)
Another large snowball is falling toward the Sun.  Comet Garradd was discovered two years ago by Gordon Garradd in Australia, and is currently visible through a small telescope at visual magnitude nine.  Officially designated C/2009 P1 (Garradd), the comet will likely continue to brighten, with recent projections placing it at peak magnitude six or seven in February 2012, just below naked eye visibility.  Comet Garradd is already showing a short tail and is seen as the elongated fuzzy patch in the above negative image recorded earlier this month from Yellow Springs, Ohio, USA. Other comets are also currently falling into the inner Solar System and brightening as well, including C/2010 X1 (Elenin), expected to peak near magnitude six in early September, 45P/Honda-Mrkos-Pajdusakova expected to peak brighten past magnitude eight in mid-August, and C/2011 L4 (PANSTARRS) which may become visible to the unaided eye during the early months of 2013.
NGC 6188 and NGC 6164 (2011-07-28)
Fantastic shapes lurk in clouds of glowing hydrogen gas in NGC 6188. The emission nebula is found near the edge of a large molecular cloud, unseen at visible wavelengths, in the southern constellation Ara, about 4,000 light-years away. Massive, young stars of the embedded Ara OB1 association were formed in that region only a few million years ago, sculpting the dark shapes and powering the nebular glow with stellar winds and intense ultraviolet radiation. The recent star formation itself was likely triggered by winds and supernova explosions, from previous generations of massive stars, that swept up and compressed the molecular gas. Joining NGC 6188 on this cosmic canvas is rare emission nebula NGC 6164, also created by one of the region's massive O-type stars. Similar in appearance to many planetary nebulae, NGC 6164's striking, symmetric gaseous shroud and faint halo surround its bright central star at the upper right. The field of view spans about two full Moons, corresponding to 70 light years at the estimated distance of NGC 6188.
Gale Crater (2011-07-29)
This sharp view from the Thermal Emission Imaging System camera on NASA's Mars Odyssey orbiter is centered on 154 kilometer (96 mile) wide Gale crater, near the martian equator. Within Gale, an impressive layered mountain rises about 5 kilometers (3 miles) above the crater floor. Layers and structures near its base are thought to have been formed in ancient times by water-carried sediments. In fact, a spot near the crater's northern side at the foot of the mountain has now been chosen as the target for the Mars Science Laboratory mission. Scheduled for launch late this year, the mission will land Mars' next visitor from planet Earth in August of 2012, lowering the car-sized Curiosity rover to the martian surface with a hovering, rocket-powered skycrane. Curiosity's science instruments are intended to discover if Gale once had favorable environmental conditions for supporting microbial life and for preserving clues about whether life ever existed on the Red Planet.
A Tale of Two Hemispheres (2011-07-30)
A quest to find planet Earth's darkest night skies led to this intriguing panorama. In projection, the mosaic view sandwiches the horizons visible in all-sky images taken from the northern hemisphere's Canary Island of La Palma (top) and the south's high Atacama Desert between the two hemispheres of the Milky Way Galaxy. The photographers' choice of locations offered locally dark skies enjoyed by La Palma's Roque de los Muchachos Observatory and Paranal Observatory in Chile. But it also allowed the directions to the Milky Way's north and south galactic poles to be placed near the local zenith. That constrained the faint, diffuse glow of the plane of the Milky Way to the mountainous horizons. As a result, an even fainter S-shaped band of light, sunlight scattered by dust along the solar system's ecliptic plane, can be completely traced through both northern and southern hemisphere night skies.
Metal on the Plains of Mars (2011-07-31)
What has the Opportunity rover found on Mars?  While traversing a vast empty plain in 2005 in Meridiani Planum, one of Earth's rolling robots on Mars found a surprise when visiting the location of its own metallic heat shield discarded last year during descent.  The surprise is the rock visible on the lower left, found to be made mostly of dense metals iron and nickel.  The large cone-shaped object behind it -- and the flank piece on the right -- are parts of Opportunity's jettisoned heat shield.  Smaller shield debris is also visible.  Scientists do not think that the basketball-sized metal "Heat Shield Rock" originated on Mars, but rather is likely an ancient metallic meteorite.   In hindsight, finding a meteorite in a vast empty dust plain on Mars might be considered similar to Earth meteorites found on the vast empty ice plains of Antarctica. The finding raises speculations about the general abundance of rocks on Mars that have fallen there from outer space.
Shuttle Reentry Streak from Orbit (2011-08-01)
What's that strange bright streak? It is the last image ever of a space shuttle from orbit.  A week and a half ago, after decoupling from the International Space Station, the Space Shuttle Atlantis fired its rockets for the last time, lost its orbital speed, and plummeted back to Earth. Within the next hour, however, the sophisticated space machine dropped its landing gear and did what used to be unprecedented -- landed like an airplane on a runway. Although the future of human space flight from the USA will enter a temporary lull, many robotic spacecraft continue to explore our Solar System and peer into our universe, including Cassini, Chandra, Chang'e 2, Dawn, Fermi, Hubble, Kepler, LRO, Mars Express, Messenger, MRO, New Horizons, Opportunity, Planck, Rosetta, SDO, SOHO, Spitzer, STEREO, Swift, Venus-Express, and WISE.
Asteroid Vesta Full Frame (2011-08-02)
Why is the northern half of asteroid Vesta more heavily cratered than the south? No one is yet sure.  This unexpected mystery has come to light only in the past few weeks since the robotic Dawn mission became the first spacecraft to orbit the second largest object in the asteroid belt between Mars and Jupiter. The northern half of Vesta, seen on the upper left of the above image, appears to show some of the densest cratering in the Solar System, while the southern half is unexpectedly smooth.  Also unknown is the origin of grooves that circle the asteroid nears its equator, particularly visible on this Vesta rotation movie, and the nature of dark streaks that delineate some of Vesta's craters, for example the crater just above the the image center. As Dawn spirals in toward Vesta over the coming months, some answers may emerge, as well as higher resolution and color images. Studying 500-km diameter Vesta is yielding clues about its history and the early years of our Solar System.
The Leo Triplet Galaxies from VST (2011-08-03)
This popular group is famous as the Leo Triplet - a gathering of three magnificent galaxies in one field of view. Crowd pleasers when imaged with even modest telescopes, these galaxies can be introduced individually as NGC 3628 (left), M66 (bottom right), and M65 (top right). All three are large spiral galaxies. They tend to look dissimilar because their galactic disks are tilted at different angles to our line of sight. NGC 3628 is seen edge-on, with obscuring dust lanes cutting across the plane of the galaxy, while the disks of M66 and M65 are both inclined enough to show off their spiral structure. Gravitational interactions between galaxies in the group have also left telltale signs, including the warped and inflated disk of NGC 3628 and the drawn out spiral arms of M66. This gorgeous deep view of the region was taken by the new VLT Survey Telescope (VST) and spans about one degree (two full moons) on the sky. The field covers over 500 thousand light-years at the trio's estimated distance of 30 million light-years.
A Dusty Iris Nebula (2011-08-04)
These clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula and dutifully cataloged as NGC 7023, this is not the only nebula in the sky to evoke the imagery of flowers. Surrounding it, obscuring clouds of dust and cold molecular gas are also present and can suggest other convoluted and fantastic shapes. Within the Iris, the dusty nebular material surrounds a hot, young star. The dominant color of the brighter reflection nebula is blue, characteristic of dust grains reflecting starlight. Central filaments of the cosmic dust glow with a faint reddish photoluminesence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs. At the estimated distance of the Iris Nebula this remarkable wide field view is over 30 light-years across.
A Summer Night's Dream (2011-08-05)
Fix your digital camera to a tripod, start a long series of exposures, and you too can record star trails. The concentric arcs traced by the stars as planet Earth rotates on its axis often produce dreamlike scenes in otherwise familiar situations. Fall asleep, though, and the results might surprise you. Setting up on a summer night, photographer Mike Rosinski began his exposures, initially planning to capture about 45-55 minutes worth of star trails from his yard in Hartland, Michigan, USA. But he dozed, only to awaken some 3 hours later to find his camera had continued to run until the battery died. Composing the resulting images, the graceful concentric star trails were expected, along with light from a late rising Moon glinting on windows. Still, as he slept on the warm night a blizzard of yellow streaks flooded the scene, not left by fairies but fireflies.
Comet Garradd and Messier 15 (2011-08-06)
Recorded on August 2, this telescopic composite image catches Comet Garradd (C/2009 P1) in the same field of view as globular star cluster M15. The celestial scene would have been a rewarding one for influential 18th century comet hunter Charles Messier. While Messier scanned French skies for comets, he carefully cataloged positions of things which might be fuzzy and comet-like in appearance but did not move against the background stars and so were definitely not comets. M15 (lower right), the 15th entry in his famous not-a-comet catalog, is now understood to be a cluster of over 100,000 stars some 35,000 light-years distant. The comet, discovered in August 2009 by astronomer G. J. Garradd (Siding Spring Observatory, Australia) is currently sweeping across the constellation Pegasus, some 13 light-minutes from Earth. Shining faintly around 9th magnitude, comet Garradd will brighten in the coming months, predicted to be just below naked eye visibility near its peak in February 2012.
MyCn18: An Hourglass Planetary Nebula (2011-08-07)
The sands of time are running out for the central star of this hourglass-shaped planetary nebula. With its nuclear fuel exhausted, this brief, spectacular, closing phase of a Sun-like star's life occurs as its outer layers are ejected - its core becoming a cooling, fading white dwarf. In 1995, astronomers used the Hubble Space Telescope (HST) to make a series of images of planetary nebulae, including the one above.  Here, delicate rings of colorful glowing gas (nitrogen-red, hydrogen-green, and oxygen-blue) outline the tenuous walls of the hourglass. The unprecedented sharpness of the HST images has revealed surprising details of the nebula ejection process that are helping to resolve the outstanding mysteries of the complex shapes and symmetries of planetary nebulas.
Seasonal Dark Streaks on Mars (2011-08-08)
What is causing these dark streaks on Mars? A leading hypothesis is flowing -- but quickly evaporating -- water. The streaks, visible in dark brown near the image center, appear in the Martian spring and summer but fade in the winter months, only to reappear again the next summer. These are not the first markings on Mars that have been interpreted as showing the effects of running water, but they are the first to add the clue of a seasonal dependence. The above picture, taken in May, digitally combines several images from the the HiRISE instrument on the Mars Reconnaissance Orbiter (MRO). The image is color-enhanced and depicts a slope inside Newton crater  in a mid-southern region of Mars. The streaks bolster evidence that water exists just below the Martian surface in several locations, and therefore fuels speculation that Mars might harbor some sort of water-dependent life.  Future observations with robotic spacecraft orbiting Mars, such as MRO,  Mars Express, and Mars Odyssey will continue to monitor the situation and possibly confirm -- or refute -- the exciting flowing water hypothesis.
The Summer Triangle Over Catalonia (2011-08-10)
Can you find the Summer Triangle?  It's not hard to find this famous triangle of stars this time of year from northern locations.  Just look straight up after sunset and find three of the brightest stars in the sky that nearly form a triangle. Then compare these stars to sky images like the one shown above, or hold up a smart phone running a good sky labelling application.  The three stars that form the vertexes of the Summer Triangle are Vega, Deneb, and Altair.  Pictured above is a 360 degree full sky projection framing not only the Summer Triangle but the great arch of our Milky Way Galaxy. The image was taken last week in front of a small river that encircles the historic town of Sant Lloren� de la Muga in Catalonia, northeastern Spain.