In this image taken by the Hubble Space Telescope, an unusual, ghostly green blob of gas appears to float near a neighboring spiral galaxy.
The bizarre object, dubbed Hanny's Voorwerp (Hanny's Object in Dutch), is the only visible part of a 300,000-light-year-long streamer of gas stretching around the galaxy, called IC 2947. The greenish Voorwerp is visible because a beam of light from the galaxy's core illuminated it. This beam came from a quasar--a bright, energetic object powered by a black hole. The quasar may have turned off about 200,000 years ago.
This Hubble view uncovers a pocket of star clusters, the yellowish-orange area at the tip of Hanny's Voorwerp. The star clusters are confined to an area that is a few thousand light- years wide. The youngest stars are a couple of million years old. The Voorwerp is the size of our Milky Way galaxy, and its bright green color is from glowing oxygen.
An interaction between IC 2947 and another galaxy about a billion years ago may have created Hanny's Voorwerp and fueled the quasar. The Hubble image shows that IC 2947 has been disturbed, with complex dust patches, warped spiral arms, and regions of star formation around its core. These features suggest the aftermath of a galaxy merger. The bright spots in the central part of the galaxy are star-forming regions. The small, pinkish object to the lower right of IC 2397 is an edge-on spiral galaxy in the background.
The image was made by combining data from the Advanced Camera for Surveys and the Wide Field Camera 3. The ACS exposures were taken April 12, 2010; the WFC3 data, April 4, 2010.
Image Credit: NASA, ESA, W. Keel (University of Alabama) and the Galaxy Zoo Team