Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2003 August 21
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X-Rays from M17
Credit: L. Townsley (PSU) et al., CXC, NASA

Explanation: About 5,000 light-years away, toward the constellation Sagittarius and the center of our galaxy, lies the bright star forming region cataloged as M17. In visible light, M17's bowed and hollowed-out appearance has resulted in many popular names like the Horseshoe, Swan, Omega, and Lobster nebula. But what has sculpted this glowing gas cloud? This Chandra Observatory image of x-rays from M17 provides a clue. Many massive young stars are responsible for the pink central region of the false-color x-ray picture, their colliding stellar winds producing the multimillion degree gas cloud which extends ten or so light-years to the left. When compared with visible light images, this x-ray hot cloud is partly surrounded by the nebula's cooler gas. In fact, having carved out a central cavity the hot gas seems to be flowing out of the horseshoe shape like champagne from an uncorked bottle ... suggesting yet another name for star forming region M17.

Tomorrow's picture: finally Friday

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