NASA's Swift satellite makes best-ever ultraviolet portrait of Andromeda galaxy

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Washington, September 17 (ANI): NASA's Swift satellite has acquired the highest-resolution view of a neighboring spiral galaxy ever attained in the ultraviolet.

The galaxy, known as M31 in the constellation Andromeda, is the largest and closest spiral galaxy to our own.

"Swift reveals about 20,000 ultraviolet sources in M31, especially hot, young stars and dense star clusters," said Stefan Immler, a research scientist on the Swift team at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

"Of particular importance is that we have covered the galaxy in three ultraviolet filters. That will let us study M31's star-formation processes in much greater detail than previously possible," he added.

M31, also known as the Andromeda Galaxy, is more than 220,000 light-years across and lies 2.5 million light-years away.

On a clear, dark night, the galaxy is faintly visible as a misty patch to the naked eye.

Between May 25 and July 26, 2008, Swift's Ultraviolet/Optical Telescope (UVOT) acquired 330 images of M31 at wavelengths of 192.8, 224.6, and 260 nanometers.

The images represent a total exposure time of 24 hours.

The task of assembling the resulting 85 gigabytes of images fell to Erin Grand, an undergraduate student at the University of Maryland at College Park who worked with Immler as an intern this summer.

"After ten weeks of processing that immense amount of data, I'm extremely proud of this new view of M31," she said.

Several features are immediately apparent in the new mosaic.

The first is the striking difference between the galaxy's central bulge and its spiral arms.

"The bulge is smoother and redder because it's full of older and cooler stars," Immler explained. "Very few new stars form here because most of the materials needed to make them have been depleted," he added.

Dense clusters of hot, young, blue stars sparkle beyond the central bulge.

M31's disk and spiral arms contain most of the gas and dust needed to produce new generations of stars.

Star clusters are especially plentiful in an enormous ring about 150,000 light-years across.

"Swift is surveying nearby galaxies like M31 so astronomers can better understand star- formation conditions and relate them to conditions in the distant galaxies where we see gamma-ray bursts occurring," said Neil Gehrels, the mission's principal investigator at NASA Goddard. (ANI)

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