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 Sat, 07 Nov 2009 14:06:01 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/ap091107.html Sat, 07 Nov 2009 14:06:01 GMT Stickney Crater, the largest crater on the martian moon Phobos, is named for Chloe Angeline Stickney Hall, mathematician and wife of astronomer Asaph Hall. Asaph Hall discovered both the Red Planet's moons in 1877. Over 9 kilometers across, Stickney is nearly half the diameter of Phobos itself, so large that the impact that blasted out the crater likely came close to shattering the tiny moon. This stunning, enhanced-color image of Stickney and surroundings was recorded by the HiRISE camera onboard the Mars Reconnaissance Orbiter as it passed within some six thousand kilometers of Phobos in March of 2008. Even though the surface gravity of asteroid-like Phobos is less than 1/1000th Earth's gravity, streaks suggest loose material has slid down inside the crater walls over time. Light bluish regions near the crater's rim could indicate a relatively freshly exposed surface. The origin of the curious grooves along the surface is mysterious but may be related to the crater-forming impact. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091106.html Fri, 06 Nov 2009 14:06:01 GMT A familiar sight to sky enthusiasts with even a small telescope, the Ring Nebula (M57) is some 2,000 light-years away in the musical constellation Lyra. The central ring is about one light-year across, but this remarkably deep exposure - a collaborative effort combining data from three different telescopes - explores the looping filaments of glowing gas extending much farther from the nebula's central star. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from a dying, sun-like star. This remarkable composite image includes narrowband image data recording the Ring's atomic hydrogen emission (shown as violet) in visible light and molecular hydrogen emission (shown as red) at near infrared wavelengths. The much more distant spiral galaxy IC 1296 is also visible at the upper right. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091105.html Thu, 05 Nov 2009 14:06:01 GMT Illuminating the landscape all through the night of November 2nd, this week's bright Full Moon was known in the northern hemisphere as a Hunter's Moon. But this dramatic view of the shining lunar orb, from Sobreda, Portugal, was captured just a few nights earlier, on Halloween. In the spirit of the season, the image plays a little trick. The picture is actually two digital photos - one short and one long exposure. They were combined to bring out the details of the bright lunar surface and the fainter features in the dark, surrounding clouds, in a single image. Of course, you may recognize some of the spookier shapes in the clouds as having visited your neighborhood last week, along with Halloween's Moon. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091104.html Wed, 04 Nov 2009 14:06:01 GMT Our Sun may look like all soft and fluffy, but it's not. Our Sun is an extremely large ball of bubbling hot gas, mostly hydrogen gas. The above picture of our Sun was taken last month in a specific red color of light emitted by hydrogen gas called Hydrogen-alpha and then color inverted to appear blue. In this light, details of the Sun's chromosphere are particularly visible, highlighting numerous thin tubes of magnetically-confined hot gas known as spicules rising from the Sun like bristles from a shag carpet. Our Sun glows because it is hot, but it is not on fire. Fire is the rapid acquisition of oxygen, and there is very little oxygen on the Sun. The energy source of our Sun is the nuclear fusion of hydrogen into helium deep within its core. No sunspots or large active regions were visible on the Sun this day, although some solar prominences are visible around the edges. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091103.html Tue, 03 Nov 2009 14:06:01 GMT On the upper right, dressed in blue, is the Pleiades. Also known as the Seven Sisters and M45, the Pleiades is one of the brightest and most easily visible open clusters on the sky. The Pleiades contains over 3,000 stars, is about 400 light years away, and only 13 light years across. Surrounding the stars is a spectacular blue reflection nebula made of fine dust. A common legend is that one of the brighter stars faded since the cluster was named. On the lower left, shining in red, is the California Nebula. Named for its shape, the California Nebula is much dimmer and hence harder to see than the Pleiades. Also known as NGC 1499, this mass of red glowing hydrogen gas is about 1,500 light years away. Although about 25 full moons could fit between them, the above wide angle, deep field image composite has captured them both. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091102.html Mon, 02 Nov 2009 14:06:01 GMT Last week, NASA test fired a new rocket. The Ares 1-X was the first non-shuttle rocket launched from Kennedy Space Center since the Saturn launched humans to Earth orbit and the Moon in the 1960s and 1970s. NASA is testing Ares as a prelude to replacing the aging space shuttle fleet. The tremendous thrust of the Ares 1-X can bring the massive rocket from a standing start to a vertical speed of over 100 kilometers per hour in under eight seconds. The test rocket launched last week was longer than a football field and covered with over 700 sensors to record data that will enable engineers to refine details of future Ares rockets. Pictured above, the Ares 1-X blasts into space while the top part of the rocket becomes engulfed in a shock collar of water droplets likely created by the sudden drop of air pressure. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091101.html Sun, 01 Nov 2009 14:06:02 GMT What color is the universe? More precisely, if the entire sky was smeared out, what color would the final mix be? This whimsical question came up when trying to determine what stars are commonplace in nearby galaxies. The answer, depicted above, is a conditionally perceived shade of beige. To determine this, astronomers computationally averaged the light emitted by one of the largest sample of galaxies yet analyzed: the 200,000 galaxies of the 2dF survey. The resulting cosmic spectrum has some emission in all parts of the electromagnetic spectrum, but a single perceived composite color. This color has become much less blue over the past 10 billion years, indicating that redder stars are becoming more prevalent. In a contest to better name the color, notable entries included skyvory, univeige, and the winner: cosmic latte. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091031.html Sat, 31 Oct 2009 13:06:01 GMT Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula VdB 152 really is very faint. Far from your neighborhood on this Halloween Night, the cosmic phantom is nearly 1,400 light-years away. Also cataloged as Ced 201, it lies along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of interstellar dust in the region block light from background stars or scatter light from the embedded bright star giving parts of the nebula a characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through space is very different from the cloud's velocity. This deep telescopic image of the region spans about 7 light-years. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091030.html Fri, 30 Oct 2009 13:06:01 GMT To the eye, this cosmic composition nicely balances the Bubble Nebula at the upper right with open star cluster M52. The pair would be lopsided on other scales, though. Embedded in a complex of interstellar dust and gas and blown by the winds from a single, massive O-type star, the Bubble Nebula (aka NGC 7635) is a mere 10 light-years wide. On the other hand, M52 is a rich open cluster of around a thousand stars. The cluster is about 25 light-years across. Seen toward the northern boundary of Cassiopeia, distance estimates for the Bubble Nebula and associated cloud complex are around 11,000 light-years, while star cluster M52 lies nearly 5,000 light-years away. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091029.html Thu, 29 Oct 2009 13:06:01 GMT An unusual triangle of light is visible this time of year just before dawn, in the northern hemisphere. Once considered a false dawn, this triangle of light is actually Zodiacal Light, light reflected from interplanetary dust particles. The bright reflecting triangle is clearly visible on the right of the above image taken from Laguna Verde near Valparaíso, Chile in late July. The band of our Milky Way Galaxy on the left mirrors the zodiacal band. Zodiacal dust orbits the Sun predominantly in the same plane as the planets: the ecliptic. Zodiacal light is so bright in the north this time of year because the dust band is oriented nearly vertical at sunrise, so that the thick air near the horizon does not block out relatively bright reflecting dust. Zodiacal light is also bright for people in Earth's northern hemisphere in March and April just after sunset. In the southern hemisphere, zodiacal light is most notable after sunset in late summer, and brightest before sunrise in late spring. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091028.html Wed, 28 Oct 2009 13:06:01 GMT What if we could see back to the beginning of the universe? We can -- since it takes the age of the universe for light to cross the universe. Peering at distant objects, therefore, tells us about how the universe used to be, even near its beginning. Since telescopes are therefore also time portals, observations of distant clusters can be used, for example, to investigate when and how these huge galaxy conglomerations formed. Previously, the redshift record for a galaxy cluster was about 1.5, corresponding to about nine billion light years distant. Recently, using data including X-ray images from the orbiting Chandra X-Ray Observatory, a new furthest cluster was identified. Shown above, JKCS041 is seen at redshift 1.9, corresponding to nearly one billion light years further than the previous record holder. The hot X-ray gas that confirmed the apparent galaxy grouping as a true cluster of galaxies is shown above in diffuse blue, superposed on an optical image showing many foreground stars. JKCS041 is seen today as it appeared at only one quarter of the present age of the universe. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091027.html Tue, 27 Oct 2009 13:06:01 GMT In cosmic brush strokes of glowing hydrogen gas, this beautiful skyscape unfolds across the plane of our Milky Way Galaxy and the center of the northern constellation Cygnus the Swan. Recorded from a premier remote observatory site (ROSA) in southern France, the image spans about 6 degrees. Bright supergiant star Gamma Cygni near image center lies in the foreground of the complex gas and dust clouds and crowded star fields. Left of Gamma Cygni, shaped like two luminous wings divided by a long dark dust lane is IC 1318, whose popular name is understandably the Butterfly Nebula. The more compact, bright nebula at the lower right is NGC 6888, the Crescent Nebula. Some distance estimates for Gamma Cygni place it at around 750 light-years while estimates for IC 1318 and NGC 6888 range from 2,000 to 5,000 light-years. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091026.html Mon, 26 Oct 2009 13:06:01 GMT You, too, can Zoo. The Galaxy Zoo project has been enabling citizen scientists -- inquisitive people like yourself armed with only a web browser-- to sort through the universe. Specifically, after a brief training session, volunteers are asked to use the superior image-processing power of their minds to classify and measure properties of galaxies in the vast Sloan Digital Sky Survey. In its two short years of existence, millions of galaxies have already been inspected by thousands of enthusiastic volunteers. Using Galaxy Zoo data, for example, the universe has been discovered to create no preferred spin direction, an unusual and unclassified object was found that is still being investigated, and a whole class of small galaxies dubbed Green Peas were uncovered where star formation occurs at an extraordinary high rate. Further, the Galaxy Zoo may be setting a precedent for a new type of scientific inquiry where the web helps collect, focus and coordinate human and machine intelligence. Pictured above, a group of vibrant mergers found by Zooites demonstrates the diverse zoo-like nature of many interacting galaxies in the universe. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091025.html Sun, 25 Oct 2009 13:06:01 GMT This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The above image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091024.html Sat, 24 Oct 2009 13:06:00 GMT Big, beautiful spiral galaxy NGC 7331 is often touted as an analog to our own Milky Way. About 50 million light-years distant in the northern constellation Pegasus, NGC 7331 was recognized early on as a spiral nebula and is actually one of the brighter galaxies not included in Charles Messier's famous 18th century catalog. Since the galaxy's disk is inclined to our line-of-sight, long telescopic exposures often result in an image that evokes a strong sense of depth. The effect is further enhanced in this deep image by the galaxies that lie beyond the gorgeous island universe. The background galaxies are about one tenth the apparent size of NGC 7331 and so lie roughly ten times farther away. Their strikingly close alignment on the sky with NGC 7331 occurs just by chance. The visual grouping of galaxies is also known as the Deer Lick Group. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091023.html Fri, 23 Oct 2009 13:06:02 GMT Driving along on a summer evening, near the small town of Weikersheim in southern Germany, photographer Jens Hackmann had to stop. He couldn't resist pointing his camera and telephoto lens at this lovely conjunction of a Full Moon and planet Jupiter looming near the steeple of a local church. Of course, 400 years ago, Galileo couldn't resist pointing his newly constructed telescope at these celestial beacons either. When he did, he found craters and mountains on the not-so-smooth lunar surface and discovered the large moons of Jupiter now known as the Galilean Moons. Jupiter's Galilean moons are just visible in this photo as tiny pinpricks of light very near the bright planet. Want to see the Moon and Jupiter better than Galileo? Look for local 2009 International Year of Astronomy activities and events during these next few Galilean Nights (October 22-24). ]]> http://antwrp.gsfc.nasa.gov/apod/ap091022.html Thu, 22 Oct 2009 13:06:01 GMT Last Friday, a gathering of three bright planets and the Moon graced the morning sky. With Mercury, Venus, Saturn, and a narrow lunar crescent close to the eastern horizon in the dawn twilight, this picture of the beautiful conjunction was recorded near Noerdlingen, Germany. These planets are wandering apart now and Mercury is sinking closer toward the rising Sun. But if you also scan the rest of the sky this week you should be able to add Jupiter and Mars to your planet spotting list, with Mars rising around midnight and Jupiter shining brightly after sunset. In fact, if you want a better view of Jupiter than Galileo had, you might check out the 2009 International Year of Astronomy activities and events during these next few Galilean Nights (October 22-24). ]]> http://antwrp.gsfc.nasa.gov/apod/ap091021.html Wed, 21 Oct 2009 13:06:01 GMT Who's been marking up Mars? This portion of a recent high-resolution picture from the HiRISE camera on board the Mars Reconnaissance Orbiter shows twisting dark trails criss-crossing light colored terrain on the martian surface. Newly formed trails like these had presented researchers with a tantalizing martian mystery but are now known to be the work of miniature wind vortices known to occur on the red planet - martian dust devils. Such spinning columns of rising air heated by the warm surface are also common in dry and desert areas on planet Earth. Typically lasting only a few minutes, dust devils becoming visible as they pick up loose red-colored dust leaving the darker and heavier sand beneath intact. On Mars, dust devils can be up to 8 kilometers high. Dust devils have been credited with unexpected cleanings of mars rover solar panels. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091020.html Tue, 20 Oct 2009 13:06:01 GMT What does a solar prominence look like in three dimensions? To help find out, NASA launched the STEREO satellites to keep a steady eye on the Sun from two different vantage points. The STEREO satellites orbit the Sun nearly along Earth's orbit, but one (dubbed Ahead) currently leads the Earth, while the other (dubbed Behind) currently trails. Three weeks ago, a powerful prominence erupted and remained above the Sun for about 30 hours, allowing the STEREO satellites to get numerous views of the prominence from different angles. Pictured above is a high-resolution image of the event from the STEREO Ahead satellite. A video of the prominence erupting as seen from both spacecraft can be found here. The unusually quiet nature of the Sun over the past two years has made large prominences like this relatively rare. The combined perspective of STEREO will help astronomers better understand the mechanisms for the creation and evolution of prominences, coronal mass ejections, and flares. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091019.html Mon, 19 Oct 2009 13:06:01 GMT It was along the way. The robotic rover Opportunity currently rolling across the Meridiani Plain on Mars has a destination of Endeavour Crater, a large crater over 20 kilometers across which may yield additional clues about the cryptic past of ancient Mars. Besides passing open fields of dark soil and light rock, Opportunity has chanced upon several interesting features. One such feature, pictured above in a digitally stitched and horizontally compressed panorama, is Nereus Crater, a small crater about 10 meters across that is surrounded by jagged rock. Besides Nereus, Opportunity recently also happened upon another unusual rock -- one that appears to be the third large meteorite found on Mars and the second for Opportunity during only this trip. Opportunity has been traveling toward Endeavour Crater for over a year now, and if it can avoid ridged rocks and soft sand along the way, it may reach Endeavour sometime next year. ]]> http://antwrp.gsfc.nasa.gov/apod/ap091018.html Sun, 18 Oct 2009 13:06:01 GMT Towering pillars of cold gas and dark dust adorn the center star forming region of Sharpless 171. An open cluster of stars is forming there from the gas in cold molecular clouds. As energetic light emitted by young massive stars boils away the opaque dust, the region fragments and picturesque pillars of the remnant gas and dust form and slowly evaporate. The energetic light also illuminates the surrounding hydrogen gas, energize it to glow as a red emission nebula. Pictured above is the active central region of the Sharpless 171 greater emission nebula. Sharpless 171 incorporates NGC 7822 and the active region imaged above. The area above spans about 20 light years, lies about 3,000 light years away, and can be seen with a telescope toward the northern constellation of the King of Ethiopia (Cepheus). ]]>