NASA Astronomy Pictures Of The Day [Week 5/2010]
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► Stardust in Perseus
This cosmic expanse of dust, gas, and stars covers close to three degrees on the sky in the heroic constellation Perseus. Right of center in the gorgeous skyscape is the dusty blue reflection nebula NGC 1333, about 1,000 light-years away. At that estimated distance, the field of view is about 50 light-years across. Next to NGC 1333 is the reddish glow of shocked hydrogen gas created by energetic jets and winds from stars in the process of formation.
► Shepherd Moon Prometheus from Cassini
Another moon of Saturn has been imaged in detail by the Cassini spacecraft. Visible in an unprocessed image from 36,000 kilometers away, Prometheus’ 100-km long surface was revealed to have an interesting system of bulges, ridges, and craters. Cassini’s next major targeted flyby is of the moon Rhea.
► Hong Kong Sky
This remarkable scene combines multiple exposures recorded from a waterside perspective in Hong Kong, China. It follows a young crescent Moon, with brilliant planet Jupiter to its left, as they set together in the western sky. Their two luminous trails are faintly paralleled by trails of background stars.
► The Einstein Cross Gravitational Lens
Most galaxies have a single nucleus — does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar. The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images. The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident. The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross.
► Mars and a Colorful Lunar Fog Bow
Even from the top of a volcanic crater, this vista was unusual. For one reason, Mars (on the far upper left) was dazzlingly bright when this picture was taken, as it was nearing its brightest time of the entire year.
► P/2010 A2: Unusual Asteroid Tail Implies Powerful Collision
First discovered on ground based LINEAR images, the object appeared unusual enough to investigate further with the Hubble Space Telescope. What Hubble saw indicates that P/2010 A2 is unlike any object ever seen before. At first glance, the object appears to have the tail of a comet. Close inspection, however, shows a 140-meter nucleus offset from the tail center, very unusual structure near the nucleus, and no discernable gas in the tail. Knowing that the object orbits in the asteroid belt between Mars and Jupiter, a preliminary hypothesis that appears to explain all of the known clues is that P/2010 A2 is the debris left over from a recent collision between two small asteroids. If true, the collision likely occurred at over 15,000 kilometers per hour — five times the speed of a rifle bullet — and liberated energy in excess of a nuclear bomb.
► Dust Storm on Mars
It’s spring for the northern hemisphere of Mars and spring on Mars usually means dust storms. So the dramatic brown swath of dust (top) marking the otherwise white north polar cap in this picture of the Red Planet is not really surprising.
► The Colors of IC 1795
This colorful cosmic portrait features glowing gas and obscuring dust clouds in IC 1795, a star forming region in the northern constellation Cassiopeia. The nebula’s colors were created by adopting the Hubble false-color palette for mapping narrow emission from oxygen, hydrogen, and sulfur atoms to blue, green and red colors, and further blending the data with images of the region recorded through broadband filters.
► The International Space Station Over the Horizon
The STS-129 crew of the Space Shuttle Atlantis undocked from the International Space Station (ISS) and returned to Earth. As the shuttle departed the space station, they took the above image. The ISS continues to be home for five astronauts of Expedition 21.
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