juliensimon/nasa-apod huggingface dataset:
Tycho's Supernova Remnant (2009-03-17)

What star created this huge puffball?  Pictured above is the best multi-wavelength image yet of Tycho's supernova remnant, the result of a stellar explosion first recorded over 400 years ago by the famous astronomer Tycho Brahe.  The above image is a composite of an X-ray image taken by the orbiting Chandra X-ray Observatory, an infrared image taken by the orbiting Spitzer Space Telescope, and an optical image taken by the 3.5-meter Calar Alto telescope located in southern Spain. The expanding gas cloud is extremely hot, while slightly different expansion speeds have given the cloud a puffy appearance.  Although the star that created SN 1572, is likely completely gone, a star dubbed Tycho G, too dim to be easily discerned here, is being studied as the possible companion. Finding progenitor remnants of Tycho's supernova is particularly important because the supernova was recently determined to be of Type Ia.  The peak brightness of Type Ia supernovas is thought to be well understood, making them quite valuable in calibrating how our universe dims distant objects.
GLOBE at Night: Help Track Light Pollution (2009-03-18)

How many stars can you see? Through next week, the GLOBE at Night project invites people from all over the world to go outside at night, look up, and see!  Specifically, people are invited to go out an hour after sunset and look for the constellation Orion toward the west.  Rather than count Orion's stars directly, however, the GLOBE at Night website has made things easier by providing several star charts to which you can compare your view of Orion.  Possible matches extend from a bright sky where only a few Orion stars are visible, to a very dark sky where over 100 Orion stars are visible. Pictured above are results from last year's sky observation campaign. Since 2009 is the International Year of Astronomy, it is hoped that an even better map can be created this year.  By participating in this easy and fun activity, you are helping humanity to better understand how light pollution is changing across the Earth.

Image credit: Globe at Night Project,
UCAR, 
International Year of Astronomy 2009
Saturn: Moons in Transit (2009-03-19)

very 14 to 15 years, Saturn's rings are tilted edge-on to our line of sight. As the bright, beautiful rings seem to grow narrower it becomes increasingly difficult to see them, even with large telescopes. But it does provide the opportunity to watch multiple transits of Saturn's moons. During a transit, a sunlit moon and its shadow glide across the cloudy face of the gas giant. Recorded on February 24, this Hubble image is part of a sequence showing the transit of four of Saturn's moons. From left to right are Enceladus and shadow, Dione and shadow, and Saturn's largest moon Titan. Small moon Mimas is just touching Saturn's disk near the ring plane at the far right. The shadows of Titan and Mimas have both moved off the right side of the disk. Saturn itself has an equatorial diameter of about 120,000 kilometers.
Sunset at the Portara (2009-03-20)

Today, the Sun crosses the celestial equator heading north at 11:44 UT. Known as an equinox, this astronomical event marks the first day of spring in the northern hemisphere and autumn in the south. It also marks the beginning of Norouz, the Persian (Iranian) new year. Equinox means equal night. With the Sun on the celestial equator, Earth dwellers will experience nearly 12 hours of daylight and 12 hours of darkness. Of course, in the north the days will grow longer, the Sun marching higher in the sky as summer approaches. To celebrate the equinox, consider this scenic view of the setting Sun from the island of Naxos in the Aegean Sea. Recorded last June, the well-planned image captures the Portara (big door) in a dramatic silhouette. Measuring about 6 by 3.5 meters, the Portara is the large entrance to the Greek island's ancient, unfinished Temple of Apollo.

Image credit: Anthony Ayiomamitis
Fermi's Gamma-Ray Sky (2009-03-21)

Scanning the entire sky in gamma-rays, photons with over 50 million times the energy of visible light, the Fermi mission's Large Area Telescope (LAT) explores the high-energy universe. This all-sky map constructed from 3 months of LAT observations (August 4 to October 30, 2008) represents a deeper, better-resolved view of the gamma-ray sky than any previous space mission. What shines in Fermi's gamma-ray sky? A new paper describes the 205 brightest gamma-ray sources, but this map highlights a Fermi "top ten" list of five sources within, and five sources that lie beyond our Milky Way Galaxy. Within our galaxy: the Sun traces a faint arc across the map between the observation dates, LSI +61 303 is an X-ray binary star about 6,500 light-years away, PSR J1836+5925 is a type of pulsar (spinning neutron star) that is only seen to pulse at gamma-ray energies, and 47 Tuc is a globular star cluster some 15,000 light-years away. A fifth galactic source (unidentified), just above the center of the galactic plane, is intriguing because it is a variable source and has no clear counterpart at other wavelengths. Beyond our galaxy: NGC 1275 is a large galaxy at the heart of the Perseus galaxy cluster some 233 million light-years away, while 3C 454.3, PKS 1502+106, and PKS 0727-115 are active galaxies billions of light-years distant. Another unidentified source, seen below the galactic plane, is likely beyond the boundaries of the Milky Way. Its nature remains a mystery.
Sungrazer (2009-03-22)

The Sun destroyed this comet.  Arcing toward a fiery fate, this Sungrazer comet was recorded by the SOHO spacecraft's Large Angle Spectrometric COronagraph(LASCO) on 1996 Dec. 23. LASCO uses an occulting disk, partially visible at the lower right, to block out the otherwise overwhelming solar disk allowing it to image the inner 5 million miles of the relatively faint corona. The comet is seen as its coma enters the bright equatorial solar wind region (oriented vertically). Spots and blemishes on the image are background stars and camera streaks caused by charged particles. Positioned in space to continuously observe the Sun, SOHO has now been used to discover over 1,500 comets, including numerous sungrazers. Based on their orbits, they are believed to belong to a family of comets created by successive break ups from a single large parent comet which passed very near the Sun in the twelfth century. The Great Comet of 1965, Ikeya-Seki, was also a member of the Sungrazer family, coming within about 650,000 kilometers of the Sun's surface. Passing so close to the Sun, Sungrazers are subjected to destructive tidal forces along with intense solar heat. This comet, known as SOHO 6, did not survive.
The Seahorse of the Large Magellanic Cloud (2009-03-23)

It may look like a grazing seahorse, but the dark object toward the image right is actually a pillar of smoky dust about 20 light years long. The curiously-shaped dust structure occurs in our neighboring Large Magellanic Cloud, in a star forming region very near the expansive Tarantula Nebula. The energetic nebula is creating a star cluster, NGC 2074, whose center is visible just off the top of the image in the direction of the neck of the seahorse. The representative color image was taken last year by the Hubble Space Telescope's Wide Field Planetary Camera 2 in honor of Hubble's 100,000th trip around the Earth. As young stars in the cluster form, their light and winds will slowly erode the dust pillars away over the next million years.
Martian Dunes and the Shadow of Opportunity (2009-03-24)

Human made robots continue to roll across the surface of Mars. Both Opportunity and its sister rover Spirit are in their sixth year on Mars, exploring the red planet for years longer than original expectations. Pictured above is a composite of recent images taken by the navigation camera on top of the Opportunity rover in Meridiani Planum. Visible are parallel rover tracks, rippling sand dunes, light-colored bedrock protrusions, metallic rover parts, and the dark shadow of the sometimes-artistic robotic photographer. Currently, Opportunity is on its way toward huge Endeavor crater, while Spirit is trying to climb an unusual rock structure known as Home Plate. If it can survive the harsh martian environment, Opportunity should arrive at Endeavor crater in about two years, at which time it may revolutionize human knowledge of this ancient martian landform.
Orcus of the Outer Solar System (2009-03-25)

A newly discovered object in the outer Solar System moves like an anti-Pluto.  90482 Orcus was first discovered in 2004 and is slightly smaller than Pluto, although still one of the largest Kuiper belt objects known. Orcus may one day have the same IAU designation as Pluto: a dwarf planet.  Orcus and Pluto have similar orbits: each achieves nearly the same maximum and minimum distances from the Sun, each orbits on a similarly shaped ellipse, and each orbital ellipse is tilted toward the other planets' orbital ellipse by roughly the same angle.  The great mass of Neptune causes each to circle the Sun twice for every three Neptune orbits.   Orcus is like an anti-Pluto, however, because the two objects always remain across the Solar System from each other. Orcus can be found as the spot near the center of these discovery frames moving slightly down from the top.  Until the end of next week, the discoverers of Orcus ask for your help in naming its newly discovered moon.
Stars Young and Old (2009-03-26)

Galactic or open star clusters are relatively young. These swarms of stars are born near the plane of the Milky Way, but their numbers steadily dwindle as cluster members are strewn through the Galaxy by gravitational interactions. This bright open cluster, known as M46, is around 300 million years young and still contains a few hundred stars within its span of 30 light-years or so. Located about 5,000 light-years away toward the constellation Puppis, M46 also seems to contain a contradiction to its youthful status. In the lovely starscape, the colorful, circular patch just below the center of M46 (also inset at upper left) is the planetary nebula NGC 2438. Planetary nebulae are a brief, final phase in the life of a solar-type star a few billion years old whose central reservoir of hydrogen fuel has been exhausted. In fact, old NGC 2438 is estimated to be only 3,000 light-years distant and moves at a different speed than M46 cluster members. It likely represents a foreground object, only by chance appearing along our line-of-sight to young M46.

Image credit: Dark Atmospheres
The Seagull Nebula (2009-03-27)

Images from two different cameras, a digital SLR and an astronomical CCD camera, are combined in this color starscape. Both cameras made use of the same telescope at the oceanside Winter Star Party in the Florida Keys, appropriately creating this portrait of the Seagull Nebula. The wide view covers a 4x3 degree swath across the plane of the Milky Way, near the direction of Sirius, alpha star of the constellation Canis Major. Of course, the broad region includes objects with other catalog designations: notably NGC 2327 - a compact, dusty emission region with an embedded massive star that forms the bird's head (above center), and IC 2177 - forming the sweeping arc of the seagull's wings. Dominated by the reddish glow of atomic hydrogen, the complex of cosmic gas and dust clouds with bright young stars spans over 250 light-years at an estimated 3,800 light-year distance.

Image credit: Frank Barrett
Almahata Sitta 15 (2009-03-28)

Small asteroid 2008 TC3 fell to Earth at dawn on October 7, 2008, tracking through the skies over the Nubian Desert in northern Sudan. That event was remarkable because it was the first time an asteroid was detected in space before crashing into planet Earth's atmosphere. It was generally assumed the asteroid itself had completely disintegrated to dust. But, based on satellite and ground observations of the atmospheric impact event, Dr. Mauwia Shaddad of the University of Khartoum, aided by Dr. Peter Jenniskens of the SETI Institute and NASA Ames Research Center, led an expedition of students and staff to the area, combing the desert for surviving fragments. On December 6, 2008, two hours after their search began, the first meteorite was found. The team ultimately collected some 280 small meteorites, now called Almahata Sitta, with a total mass of about 5 kilograms -- the first material recovered from a known asteroid. In stark contrast to the lighter-colored stones, the black fragment in the picture is Almahata Sitta meteorite number 15. About 4 centimeters in diameter, it is seen as it came to rest on the desert floor.  Editor's note: In Arabic, Almahata Sitta is "Station Six": a railway stop in the Nubian desert where witnesses reported seeing the bright fireball meteor.

Image credit: Peter Jenniskens
(SETI Institute/NASA Ames)
Signals of a Strange Universe (2009-03-29)

even years ago results were first presented indicating that most of the energy in our universe is not in stars or galaxies but is tied to space itself.  In the language of cosmologists, a large cosmological constant is directly implied by new distant supernovae observations.  Suggestions of a cosmological constant (lambda) were not new -- they have existed since the advent of modern relativistic cosmology. Such claims were not usually popular with astronomers, though, because lambda is so unlike known universe components, because lambda's value appeared limited by other observations, and because less- strange cosmologies without lambda had previously done well in explaining the data. What is noteworthy here is the seemingly direct and reliable method of the observations and the good reputations of the scientists conducting the investigations. Over the past eleven years, independent teams of astronomers have continued to accumulate data that appears to confirm the existence of dark energy and the unsettling result of a presently accelerating universe. The above picture of a supernova that occurred in 1994 on the outskirts of a spiral galaxy was taken by one of these collaborations.
Possible Mud Volcanoes on Mars (2009-03-30)

Is this a mud volcano on Mars? If so, could it be dredging up martian microbes? This strange possibility has been suggested recently and seems to fit several recent observations of Mars. First of all, hills like this seem to better resemble mud volcanoes on Earth than lava volcanoes and impact craters on Mars. Next, the pictured dome has an unusually textured surface consistent with fractured ice. Infrared images from space indicate that hills like this cool more quickly than surrounding rock, consistent with a dried mud composition. The hills also reflect colors consistent with a composition that formed in the presence of water.  Finally, unusual plumes of gas containing methane have been found on Mars with unknown origin. These gas plumes could conceivably have been liberated by mud volcanoes, were the initially warm mud to contain methane-producing microbes drifting in a previously unobservable underground lake. A candidate mud volcano over 100 meters across is pictured above in the northern plains of Mars.
In the Heart of the Tarantula Nebula (2009-03-31)

In the heart of monstrous Tarantula Nebula lies huge bubbles of energetic gas, long filaments of dark dust, and unusually massive stars. In the center of this heart, is a knot of stars so dense that it was once thought to be a single star. This star cluster, labeled as R136 or NGC 2070, is visible just above the center of the above image and home to a great number of hot young stars.  The energetic light from these stars continually ionizes nebula gas, while their energetic particle wind blows bubbles and defines intricate filaments.  The above representative-color picture of this great LMC nebula details its tumultuous center. The Tarantula Nebula, also known as the 30 Doradus nebula, is one of the largest star-formation regions known, and has been creating unusually strong episodes of star formation every few million years.
Astronaut's Head Upgraded During Spacewalk (2009-04-01)

First, a new truss was added.  Then, new solar panels were installed. Now, as part of the planned upgrade of the International Space Station, an Expedition 18 astronaut has upgraded her own head.  The Human Extended Analog Device 9000 was attached with only minor delays, making the astronaut's remaining spacewalks over 40 percent more efficient. With the HEAD 9000 attached, an astronaut can now directly access 4 Gigabytes of computer flash memory with their own brain, perform complex mathematics by "directed thinking", and play a pre-installed game of Tetris at no additional charge.  Happy April Fools' Day from the folks at APOD.  In reality, the space shuttle Discovery's mission to upgrade the International Space Station ended Saturday after upgrading only the space station. The above image of astronaut Heidemarie Stefanyshyn-Piper handling the box-like Nitrogen Tank Assembly was actually taken last November.  For some reason, however, Astronaut Stefanyshyn-Piper can now factor 11 digit prime numbers in her head.
100 Hours of Astronomy Begins (2009-04-02)

Today, 100 Hours of Astronomy begins, a cornerstone project of the International Year of Astronomy 2009 celebrating the 400th anniversary of Galileo's original telescopic exploration of the sky. Running from April 2 through April 5, many different public programs are planned worldwide as part of the project, starting with today's opening event at the Franklin Institute in Philadelphia. Featuring one of Galileo's two remaining telescopes, the event will be webcast live. Of course, the sky examined by Galileo can still be appreciated today, with much more capable instruments that are widely available. But this skyward view from a private observatory in Veszprem, Hungary also includes objects Galileo did not see when he gazed into the night. Recorded on March 26, the image captures the paired trails of the International Space Station (the brighter trail) and the shuttle orbiter Discovery in low Earth orbit, as well as the streak of a passing airplane.

Image credit: Tamas Ladanyi
Around the World in 80 Telescopes (2009-04-03)

Want to go on an extraordinary voyage? Today you can, by watching Around the World in 80 Telescopes. The 24-hour long webcast is organized by the European Southern Observatory for the International Year of Astronomy cornerstone project 100 Hours of Astronomy. As suggested in this astronomically intense composite, the webcast event follows night and day around the globe to visit some of the most advanced observatories on Earth and in space, exploring the universe in visible light and beyond. The Gemini North Telescope (Hawaii, USA) and the large observatories at the summit of volcanic Mauna Kea are scheduled for the first stops in the program beginning April 3 at 09:00 UT. Others on the schedule include the Swift Satellite and Fermi Gamma-ray Space Telescope, the Himalayan Chandra Telescope (Hanle, India), and the 10-meter South Pole Telescope and IceCube Neutrino Telescope (South Pole, Antarctica).

Image credit: ESO /
100 Hours of Astronomy
Star Party on Planet Earth (2009-04-04)

As twilight sweeps around planet Earth tonight (April 4), many amateur astronomers will set up their telescopes for a 24-hour global star party. The planetwide star party is part of 100 Hours of Astronomy (100HA), a project of the International Year of Astronomy 2009. To join the party, members of the public can find a nearby organized event or planned webcast by consulting the schedules on the 100HA website. What could you see through a telescope tonight? For starters, a bright Moon will shine in the evening sky, offering telescopic observers spectacular views of impact craters, mountains, and lava-flooded mare. Tonight's other celestial targets include the crowd pleasing planet Saturn surrounded by its own moons, its rings tilted nearly edge-on.

Image credit: Babak Tafreshi
Orange Sun Oozing (2009-04-05)

The Sun's surface keeps changing.  Click the central arrow and watch how the Sun's surface oozes during a single hour.  The Sun's photosphere has thousands of bumps called granules and usually a few dark depressions called sunspots.  The above time-lapse movie centered on Sunspot 875 was taken in 2006 by the Vacuum Tower Telescope in the Canary Islands of Spain using adaptive optics to resolve details below 500 kilometers across.  Each of the numerous granules is the size of an Earth continent, but much shorter lived.  A granule slowly changes its shape over an hour, and can even completely disappear.  Hot hydrogen gas rises in the bright center of a granule, and falls back into the Sun along a dark granule edge.  The above movie and similar movies allows students and solar scientists to study how granules and sunspots evolve as well as how magnetic sunspot regions produce powerful solar flares.   Note: Follow the Sun today as part of 100 Hours of Astronomy
International Space Station Expands Again (2009-04-06)

The developing International Space Station (ISS) has changed its appearance again.  In a recently completed mission, the Space Shuttle orbiter Discovery visited the ISS and added components that included a new truss and new solar panels.  The entire array of expansive solar panels is visible in the above picture taken by the Discovery Crew after leaving the ISS to return to Earth.  The world's foremost space outpost can be seen developing over the past several years by comparing the above image to past images.  Also visible above are many different types of modules, a robotic arm, and a supply ship.  Construction began on the ISS in 1998.
The Colliding Spiral Galaxies of Arp 274 (2009-04-07)

Two galaxies are squaring off in Virgo and here are the latest pictures.  When two galaxies collide, the stars that compose them usually do not. This is because galaxies are mostly empty space and, however bright, stars only take up only a small fraction of that space. But during the collision, one galaxy can rip the other apart gravitationally, and dust and gas common to both galaxies does collide. If the two galaxies merge, black holes that likely resided in each galaxy center may eventually merge. Because the distances are so large, the whole thing takes place in slow motion -- over hundreds of millions of years. Besides the two large spiral galaxies, a smaller third galaxy is visible on the far left of the above image of Arp 274, also known as NGC 5679. Arp 274 spans about 200,000 light years across and lies about 400 million light years away toward the constellation of Virgo.
Unusual Dusty Galaxy NGC 7049 (2009-04-08)

How was this unusual looking galaxy created? No one is sure, especially since spiral galaxy NGC 7049 looks so strange.  NGC 7049's striking appearance is primarily due to an unusually prominent dust ring seen mostly in silhouette.  The opaque ring is much darker than the din of millions of bright stars glowing behind it. Besides the dark dust, NGC 7049 appears similar to a smooth elliptical galaxy, although featuring surprisingly few globular star clusters. NGC 7049 is pictured above as imaged recently by the Hubble Space Telescope. The bright star near the top of NGC 7049 is an unrelated foreground star in our own Galaxy.  Not visible here is an unusual central polar ring of gas circling out of the plane near the galaxy's center. Since NGC 7049 is the brightest galaxy in its cluster of galaxies, its formation might be fostered by several prominent and recent galaxy collisions. NGC 7049 spans about 150 thousand light years and lies about 100 million light years away toward the constellation of Indus.