January 10, 2011: A ghostly, glowing, green blob of gas has become one of astronomy's great cosmic mystery stories. The space oddity was spied in 2007 by Dutch high-school teacher Hanny van Arkel while participating in the online Galaxy Zoo project. The cosmic blob, called Hanny's Voorwerp (Hanny's Object in Dutch), appears to be a solitary green island floating near a normal-looking spiral galaxy, called IC 2497. Since the discovery, puzzled astronomers have used a slew of telescopes, including X-ray and radio observatories, to help unwrap the mystery. Astronomers found that Hanny's Voorwerp is the only visible part of a 300-light-year-long gaseous streamer stretching around the galaxy. The greenish Voorwerp is visible because a searchlight beam of light from the galaxy's core illuminated it. This beam came from a quasar, a bright, energetic object that is powered by a black hole. An encounter with another galaxy may have fed the black hole and pulled the gaseous streamer from IC 2497.
Now, with the help of NASA's Hubble Space Telescope, astronomers have uncovered a pocket of young star clusters (colored yellow-orange in the image) at the tip of the green-colored Hanny's Voorwerp. Hubble also shows that gas flowing from IC 2497 (the pinkish object with the swirling spiral arms) may have instigated the star birth by compressing the gas in Hanny's Voorwerp.See the rest: