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Shadows of Saturn at Equinox

Astronomy Picture of the Day - Dm, 01/09/2009 - 19:10

Shadows of Saturn at Equinox
Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

Explanation: 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.

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Open Cluster M25

Astronomy Picture of the Day - Dll, 31/08/2009 - 17:10

Open Cluster M25
Credit & Copyright: Jean-Charles Cuillandre (CFHT) & Giovanni Anselmi (Coelum Astronomia), Hawaiian Starlight

Explanation: 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).

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D. rad Bacteria: Candidate Astronauts

Astronomy Picture of the Day - Dg, 30/08/2009 - 15:10

D. rad Bacteria: Candidate Astronauts
Credit: Michael Daly (Uniformed Services University of the Health Sciences), DOE

Explanation: 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 with 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.

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NGC 7771 Galaxy Group

Astronomy Picture of the Day - Ds, 29/08/2009 - 13:10

NGC 7771 Galaxy Group
Credit & Copyright: Kent Biggs

Explanation: 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.

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NGC 7822 in Cepheus

Astronomy Picture of the Day - Dv, 28/08/2009 - 11:10

NGC 7822 in Cepheus
Credit & Copyright: Don Goldman

Explanation: 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.

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A Dark Sky Over Sequoia National Park

Astronomy Picture of the Day - Dj, 27/08/2009 - 09:10

A Dark Sky Over Sequoia National Park
Credit: D. Duriscoe, C. Duriscoe, R. Pilewski, & L. Pilewski, U.S. NPS Night Sky Program

Explanation: 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.

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Classic Orion Nebulae

Astronomy Picture of the Day - Dc, 26/08/2009 - 20:10

Classic Orion Nebulae
Credit & Copyright: Kerry-Ann Lecky Hepburn (Weather and Sky Photography)

Explanation: 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.

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Equinox at Saturn

Astronomy Picture of the Day - Dm, 25/08/2009 - 18:10

Equinox at Saturn
Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

Explanation: 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.

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Morning Glory Clouds Over Australia

Astronomy Picture of the Day - Dll, 24/08/2009 - 16:10

Morning Glory Clouds Over Australia
Credit & Licence: Mick Petroff; Tip Thanks: James Holmes (Cairns)

Explanation: 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.

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Giant Cluster Bends, Breaks Images

Astronomy Picture of the Day - Dg, 23/08/2009 - 13:10

Giant Cluster Bends, Breaks Images
Credit: NASA, ESA, H. Lee & H. Ford (Johns Hopkins U.)

Explanation: 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.

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The Gum Nebula

Astronomy Picture of the Day - Dg, 23/08/2009 - 00:10

The Gum Nebula
Credit & Copyright: Axel Mellinger

Explanation: 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.

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The Whale and the Hockey Stick

Astronomy Picture of the Day - Dv, 21/08/2009 - 22:10

The Whale and the Hockey Stick
Credit & Copyright: Josef Poepsel, Stefan Binnewies (Capella Observatory)

Explanation: 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.

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Eclipse City

Astronomy Picture of the Day - Dj, 20/08/2009 - 20:10

Eclipse City
Credit & Copyright: Alfred Lee

Explanation: 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.

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IC 1396 and Surrounding Starfield

Astronomy Picture of the Day - Dc, 19/08/2009 - 18:10

IC 1396 and Surrounding Starfield
Credit & Copyright: Thomas W. Earle

Explanation: 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.

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The Milky Way Over the Badlands

Astronomy Picture of the Day - Dm, 18/08/2009 - 16:10

The Milky Way Over the Badlands
Credit & Copyright: Wally Pacholka (AstroPics.com, TWAN)

Explanation: 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.

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Perseids from Perseus

Astronomy Picture of the Day - Dll, 17/08/2009 - 14:10

Perseids from Perseus
Credit & Copyright: Chris Peterson (Cloudbait Observatory)

Explanation: 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.

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A Laser Strike at the Galactic Center

Astronomy Picture of the Day - Dg, 16/08/2009 - 10:10

A Laser Strike at the Galactic Center
Credit: Yuri Beletsky (ESO)

Explanation: 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.

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Meteor by Moonlight

Astronomy Picture of the Day - Ds, 15/08/2009 - 21:10

Meteor by Moonlight
Credit & Copyright: Babak Tafreshi (TWAN)

Explanation: 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.

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Shuttle and Meteor

Astronomy Picture of the Day - Dv, 14/08/2009 - 19:10

Shuttle and Meteor
Credit & Copyright: Stephen Clark / Spaceflightnow.com

Explanation: This early morning skyscape was captured last week on August 4th, looking northeast across calm waters in the Turn Basin at NASA's Kennedy Space Center. In a striking contrast in motion, the space shuttle Discovery, mounted on a massive transporter, creeps toward launch pad 39A at less than two miles per hour, while a brilliant meteor streaks through the sky traveling many miles per second. Of course, this week skywatchers have seen many similar meteor streaks during the annual Perseid meteor shower. But the meteor flashing above Discovery is not likely to be one of the Perseids because its path doesn't point back to that shower's radiant. Seen here near picture center, brilliant planet Venus still dominates the sky as the Morning Star, though. Yellowish tinted Mars lies near the top of the frame and Orion's red giant star Betelgeuse is toward the right.

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Block Island Meteorite on Mars

Astronomy Picture of the Day - Dj, 13/08/2009 - 17:10

Block Island Meteorite on Mars
Credit: Mars Exploration Rover Mission, JPL, NASA

Explanation: What is this strange rock on Mars? Sitting on a smooth plane, the rock stands out for its isolation, odd shape, large size and unusual texture. The rock was discovered by the robotic Opportunity rover rolling across Mars late last month. Pictured above, Opportunity prepares to inspect the unusual rock. After being X-rayed, poked, and chemically analyzed, the rock has now been identified by Opportunity as a fallen meteorite. Now dubbed Block Island, the meteorite has been measured to be about 2/3 of a meter across and is now known to be composed mostly of nickel and iron. This is the second meteorite found by a martian rover, and so far the largest. Vast smooth spaces on Mars and Earth can make large meteorites stand out. Opportunity continues its trip across Meridiani Planum on Mars and is on schedule to reach expansive Endeavor Crater next year.

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