This unusual ghostly green blob of gas appears to float near a normal-looking spiral galaxy in the image taken by NASA’s Hubble Space Telescope. 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 IC 2497 galaxy. The object is visible because a searchlight beam of light from a quasar in the galaxy’s core illuminated it. A quasar is a bright, energetic object that is powered by a super-massive black hole. The Voorwerp is the size of our Milky Way galaxy, and its bright green color is from glowing oxygen. The galaxy as well as the object are located about 650 million light-years from Earth.
An interaction between IC 2497 and another galaxy about a billion years ago may have created Hanny’s Voorwerp and fueled the quasar. The Hubble image shows that the galaxy 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.