http://www.acme.com/jef/apod/ The Astronomy Picture of the Day is a wonderful web site that puts up a different astronomy-related picture every day. However, the site does not have an RSS feed. This page fixes that deficiency. ]]> en-us Thu, 18 Mar 2010 13:06:01 GMT ACME Labs custom shell script jef@mail.acme.com webmaster@mail.acme.com http://www.acme.com/jef/apod/apod.GIF http://www.acme.com/jef/apod/ http://antwrp.gsfc.nasa.gov/apod/ap100318.html Thu, 18 Mar 2010 13:06:01 GMT What shines in the gamma-ray sky? The most complete answer yet to that question is offered by the Fermi Gamma-ray Space Telescope's first all-sky catalog. Fermi's sources of cosmic gamma-rays feature nature's most energetic particle accelerators, ultimately producing 100 MeV to 100 GeV photons, photons with more than 50 million to 50 billion times the energy of visible light. Distilled from 11 months of sky survey data using Fermi's Large Area Telescope (LAT), the 1,451 cataloged sources include energetic star burst galaxies and active galactic nuclei (AGN) far beyond the Milky Way. But within our own galaxy are many pulsars (PSR) and pulsar wind nebulae (PWN), supernova remnants (SNR), x-ray binary stars (HXB) and micro-quasars (MQO). Fermi's all sky map is shown centered on the Milky Way with the diffuse gamma-ray emission from the Galactic plane running horizontally through the frame. To locate the cataloged gamma-ray sources, just slide your cursor over the map. For now, 630 of the sources cataloged at gamma-ray energies remain otherwise unidentified, not associated with sources detected at lower energeries. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100317.html Wed, 17 Mar 2010 13:06:01 GMT Why is this small object orbiting Mars? The origin of Phobos, the larger of the two moons orbiting Mars, remains unknown. Phobos and Deimos appear very similar to C-type asteroids, yet gravitationally capturing such asteroids, circularizing their orbits, and dragging them into Mars' equatorial plane seems unlikely. Pictured above is Phobos as it appeared during last week's flyby of ESA's Mars Express, a robotic spacecraft that began orbiting Mars in 2003. Visible in great detail is Phobos' irregular shape, strangely dark terrain, numerous unusual grooves, and a spectacular chain of craters crossing the image center. Phobos spans only about 25 kilometers in length and does not having enough gravity to compress it into a ball. Phobos orbits so close to Mars that sometime in the next 20 million years, tidal deceleration will break up the rubble moon into a ring whose pieces will slowly spiral down and crash onto the red planet. The Russian mission Phobos-Grunt is scheduled to launch and land on Phobos next year. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100316.html Tue, 16 Mar 2010 13:06:01 GMT Only in the fleeting darkness of a total solar eclipse is the light of the solar corona easily visible. Normally overwhelmed by the bright solar disk, the expansive corona, the sun's outer atmosphere, is an alluring sight. But the subtle details and extreme ranges in the corona's brightness, although discernible to the eye, are notoriously difficult to photograph. Pictured above, however, using multiple images and digital processing, is a detailed image of the Sun's corona taken during the 2008 August total solar eclipse from Mongolia. Clearly visible are intricate layers and glowing caustics of an ever changing mixture of hot gas and magnetic fields. Bright looping prominences appear pink just above the Sun's limb. The next total solar eclipse will be in July but will only be visible in a thin swath of Earth crossing the southern Pacific Ocean and South America. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100315.html Mon, 15 Mar 2010 13:06:01 GMT It may appear to be day, but it's night. Those wondrous orange streaks may appear to be rays from the setting Sun, but they're actually thin clouds illuminated by the Moon as they quickly streaked toward the distant horizon. The thick clouds on the far left may appear to have many layers, but actually they are just a few simple clouds captured on numerous separate exposures. What is surely true, though, is that the above time lapse image sequence was taken over two hours, about two weeks ago, in Sounio, Greece. Also, those really are star trails swirling around the north star Polaris on the upper right of the image. But what about the building in the foreground? It may appear to be a famous ancient structure, but it's actually a small deserted church built only last century. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100314.html Sun, 14 Mar 2010 13:06:01 GMT What's happening in the middle of this massive galaxy? There, two bright sources at the center of this composite x-ray (blue)/radio (pink) image are thought to be co-orbiting supermassive black holes powering the giant radio source 3C 75. Surrounded by multimillion degree x-ray emitting gas, and blasting out jets of relativistic particles the supermassive black holes are separated by 25,000 light-years. At the cores of two merging galaxies in the Abell 400 galaxy cluster they are some 300 million light-years away. Astronomers conclude that these two supermassive black holes are bound together by gravity in a binary system in part because the jets' consistent swept back appearance is most likely due to their common motion as they speed through the hot cluster gas at 1200 kilometers per second. Such spectacular cosmic mergers are thought to be common in crowded galaxy cluster environments in the distant universe. In their final stages the mergers are expected to be intense sources of gravitational waves. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100313.html Sat, 13 Mar 2010 15:14:58 GMT ]]> http://antwrp.gsfc.nasa.gov/apod/ap100312.html Fri, 12 Mar 2010 14:06:00 GMT Who are these masked men? Technicians from Ball Aerospace and NASA at Marshall Space Flight Center's X-ray and Cryogenic Facility, of course, testing primary mirror segments of the James Webb Space Telescope (JWST). Scheduled for launch in 2014, JWST will be optimized for the infrared exploration of the early Universe, utilizing a primary mirror 21.3 feet across, composed of 18 hexagonal segments. Here, a group of JWST mirror segments are being prepared for tests to assure they meet the exacting mission requirements. The technicians' suits and masks help prevent contamination of the mirror surfaces. At the Marshall X-ray and Cryogenic Facility, the mirrors are tested in the large circular chamber after evacuating the air and cooling the chamber to -400 degrees Fahrenheit (only 60 degrees above absolute zero). The extremely low pressure and temperature simulate the JWST mirror operating environment in space. JWST mirror segment testing will continue for the next 18 months. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100311.html Thu, 11 Mar 2010 14:06:00 GMT Fixed to a tripod, a camera can record graceful trails traced by stars as planet Earth rotates on its axis. But at high latitudes during March and April, it can also capture an aurora shimmering in the night. In fact, the weeks surrounding the equinox, in both spring and fall, offer a favorable season for aurora hunters. The possibilities are demonstrated in this beautiful moonlit vista from northwestern Canadian territory the Yukon. It was taken during the early morning of March 1, off the Klondike Highway about 60 kilometers south of Dawson City. To compose the picture, many short exposures were digitally combined to follow the concentric star trail arcs while including the greenish auroral curtains also known as the northern lights. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100310.html Wed, 10 Mar 2010 14:06:01 GMT What's happening on the surface of Saturn's moon Helene? The moon was imaged in unprecedented detail last week as the robotic Cassini spacecraft orbiting Saturn swooped to within two Earth diameters of the diminutive moon. Although conventional craters and hills appear, the above raw and unprocessed image also shows terrain that appears unusually smooth and streaked. Planetary astronomers will be inspecting these detailed images of Helene to glean clues about the origin and evolution of the 30-km across floating iceberg. Helene is also unusual because it circles Saturn just ahead of the large moon Dione, making it one of only four known moons to occupy a gravitational well known as a stable Lagrange point. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100309.html Tue, 09 Mar 2010 14:06:17 GMT The two galaxies on the far left were unknown until 1968. Although they would have appeared as two of the brighter galaxies on the night sky, the opaque dust of the central band of our Milky Way Galaxy had obscured them from being seen in visible light. The above image in infrared light taken by the recently launched Wide-Field Infrared Survey Explorer (WISE), however, finds these galaxies in great detail far behind -- but seemingly next to -- the photogenic Heart nebula (IC 1805). The spiral galaxy near the top is the easiest to spot and is known as Maffei 2. Just below and to its right is fuzzy-looking Maffei 1, the closest giant elliptical galaxy to Earth. The above false-colored image spans three full moons from top to bottom. The Maffei galaxies each span about 15,000 light years across and lie about 10 million light years away toward the constellation of the Queen of Ethiopia (Cassiopeia). On the image right, stars, gaseous filaments, and warm dust highlight a detailed infrared view of the Heart nebula. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100308.html Mon, 08 Mar 2010 14:06:00 GMT What's that bright object in the sky? A common question with answers that vary by time and season, the quick answer just after sunset in middle of last month, from the norther hemisphere, was Mars. The above picturesque panorama, taken during a ski trip from the Alps in Switzerland, shows not only Mars, but much more. Pine trees line the foreground, while numerous slopes leading up to the snow covered Allalinhorn mountain are visible in the distance. Stars dot the background, with the Beehive star cluster (M44) visible just below and to the left of Mars, while stars Castor and Pollux peak through the tree tops to the Mars' upper right. Mars will remain bright and in the constellation of the Crab (Cancer) until mid-May. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100307.html Sun, 07 Mar 2010 14:06:02 GMT Is it art? If so, the paintbrush was the Spirit robotic rover, the canvas was the soil on Mars, and the artists were the scientists and engineers of the Mars Exploration Rover Mission. This panoramic picture, created in 2004 and shown above compressed horizontally, was mostly unintentional -- the MERS team was primarily instructing Spirit to investigate rocks in and around Hank's Hollow in a location called Engineering Flats on Mars. After creating the ground display with its treads, the Spirit rover was instructed to photograph the area along with itself in shadow. In 2010 as winter approaches in northern Mars, Spirit, still mired in sand, has been placed in an energy saving "hibernating" mode until spring arrives and more direct sunlight might be used to power the robotic explorer. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100306.html Sat, 06 Mar 2010 14:06:00 GMT Reddened light from the setting Sun illuminates the cloud banks hugging this snowy, rugged terrain. Inspiring a moment of quiet contemplation, the sunset scene included a remarkable pillar of light that seemed to connect the clouds in the sky with the mountains below. Known as a Sun pillar, the luminous column was produced by sunlight reflecting from flat, six-sided ice crystals formed high in the cold atmosphere and fluttering toward the ground. Last Monday, astronomers watched this Sun pillar slowly fade, as the twilight deepened and clearing, dark skies came to Mt. Jelm and the Wyoming Infrared Observatory. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100305.html Fri, 05 Mar 2010 14:06:01 GMT The plane of our Milky Way Galaxy runs right through Auriga, the Charioteer. A good part of the ancient northern constellation's rich collection of nebulae and star clusters is featured in this expansive, 10 degree wide skyscape. Bright star Elnath lies near the bottom right, linking Auriga to another constellation, Taurus, the Bull. Three open star clusters, Charles Messier's M36, M37, and M38 line up in the dense star field above and left of Elnath, familiar to many binocular-equiped skygazers. But the deep exposure also brings out the reddish emission nebulae of star-forming regions IC 405, IC 410, and IC 417. E. E. Barnard's dark nebulae B34 and B226 just stand out against a brighter background. For help identifying even more of Auriga's deep sky highlights, put your cursor over the image. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100304.html Thu, 04 Mar 2010 14:06:03 GMT Magnificent spiral galaxy NGC 4565 is viewed edge-on from planet Earth. Also known as the Needle Galaxy for its narrow profile, bright NGC 4565 is a stop on many telescopic tours of the northern sky, in the faint but well-groomed constellation Coma Berenices. This sharp, colorful image reveals the galaxy's bulging central core cut by obscuring dust lanes that lace NGC 4565's thin galactic plane. An assortment of other galaxies are included in the pretty field of view. Neighboring galaxy NGC 4562 is at the upper right. NGC 4565 itself lies about 40 million light-years distant, spanning some 100,000 light-years. Easily spotted with small telescopes, sky enthusiasts consider NGC 4565 to be a prominent celestial masterpiece Messier missed. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100303.html Wed, 03 Mar 2010 14:06:01 GMT The International Space Station (ISS) is the largest human-made object ever to orbit the Earth. The ISS is so large that it can be seen drifting overhead with the unaided eye, and is frequently imaged from the ground in picturesque fashion. Last month, the station was visited again by space shuttle, which resupplied the station and added a new module. The ISS is currently operated by the Expedition 22 crew, now consisting five astronauts including two supplied by USA's NASA, two by Russia's RKA, and one by Japan's JAXA. After departing the ISS, the crew of the space shuttle Endeavour captured the above spectacular vista of the orbiting space city high above the clouds, waters, and lands of Earth. Visible components include modules, trusses, and expansive solar arrays that gather sunlight that is turned into needed electricity. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100302.html Tue, 02 Mar 2010 14:06:01 GMT An eerie blue glow and ominous columns of dark dust highlight M78 and other bright reflection nebula in the constellation of Orion. The dark filamentary dust not only absorbs light, but also reflects the light of several bright blue stars that formed recently in the nebula. Of the two reflection nebulas pictured above, the more famous nebula is M78, in the image center, while NGC 2071 can be seen to its lower left. The same type of scattering that colors the daytime sky further enhances the blue color. M78 is about five light-years across and visible through a small telescope. M78 appears above only as it was 1600 years ago, however, because that is how long it takes light to go from there to here. M78 belongs to the larger Orion Molecular Cloud Complex that contains the Great Nebula in Orion and the Horsehead Nebula. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100301.html Mon, 01 Mar 2010 14:06:00 GMT What creates these picturesque dark streaks on Mars? No one knows for sure. A leading hypothesis is that streaks like these are caused by fine grained sand sliding down the banks of troughs and craters. Pictured above, dark sand appears to have flowed hundreds of meters down the slopes of Acheron Fossae. The sand appears to flow like a liquid around boulders, and, for some reason, lightens significantly over time. This sand flow process is one of several which can rapidly change the surface of Mars, with other processes including dust devils, dust storms, and the freezing and melting of areas of ice. The above image was taken by the HiRise camera on board the Mars Reconnaissance Orbiter which has been orbiting Mars since 2006. Acheron Fossae is a 700 kilometer long trough in the Diacria quadrangle of Mars. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100228.html Sun, 28 Feb 2010 14:06:01 GMT Why doesn't matter just bunch up? The same principle that keeps neutron stars and white dwarf stars from imploding also keeps people from imploding and makes normal matter mostly empty space. The observed reason is known as the Pauli Exclusion Principle. The principle states that identical fermions -- one type of fundamental matter -- cannot be in the same place at the same time and with the same orientation. The other type of matter, bosons, do not have this property, as demonstrated clearly by recently created Bose-Einstein condensates. Earlier this decade, the Pauli Exclusion Principle was demonstrated graphically in the above picture of clouds of two isotopes of lithium -- the left cloud composed of bosons while the right cloud is composed of fermions. As temperature drops, the bosons bunch together, while the fermions better keep their distance. The reason why the Pauli Exclusion Principle is true and the physical limits of the principle are still unknown. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100227.html Sat, 27 Feb 2010 14:06:02 GMT On February 21st, the Space Shuttle Endeavour and the International Space Station (ISS) flew through the sky near dawn over Whitby, Ontario, Canada. Along with star trails, both were captured in this single time exposure. Glinting in sunlight 350 kilometers above the Earth, Endeavour slightly preceeded the ISS arcing over the horizon. But the brighter trail and the brighter flare belongs to the space station just visted by Endeavour. Near the completion of the STS-130 mission, hours later Endeavour made a night landing at Kennedy Space Center. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100226.html Fri, 26 Feb 2010 14:06:01 GMT A jewel of the southern sky, the Great Carina Nebula, aka NGC 3372, spans over 300 light-years. Near the upper right of this expansive skycape, it is much larger than the more northerly Orion Nebula. In fact, the Carina Nebula is one of our galaxy's largest star-forming regions and home to young, extremely massive stars, including the still enigmatic variable Eta Carinae, a star with well over 100 times the mass of the Sun. Nebulae near the center of the 10 degree wide field include NGC 3576 and NGC 3603. Near center at the top of the frame is open star cluster NGC 3532, the Wishing Well Cluster. More compact, NGC 3766, the Pearl Cluster, can be spotted at the left. Anchoring the lower left of the cosmic canvas is another large star-forming region, IC 2948 with embedded star cluster IC 2944. That region is popularly known as the Running Chicken Nebula. ]]> http://antwrp.gsfc.nasa.gov/apod/ap100225.html Thu, 25 Feb 2010 14:06:02 GMT This beautiful cosmic portrait features NGC 891. The spiral galaxy spans about 100 thousand light-years and is seen almost exactly edge-on from our perspective. In fact, about 30 million light-years distant in the constellation Andromeda, NGC 891 looks a lot like our Milky Way. At first glance, it has a flat, thin, galactic disk and a central bulge cut along the middle by regions of dark obscuring dust. Also apparent in NGC 891's ege-on presentation are filaments of dust that extend hundreds of light-years above and below the center line. The dust has likely been blown out of the disk by supernova explosions or intense star formation activity. Faint neighboring galaxies can also been seen near this galaxy's disk. ]]>