Hubble scientists have released a picture of a strange green blob floating near a neighboring spiral galaxy.
The weird cloud is dubbed Hanny’s Voorwerp – Hanny’s Thing in Dutch – and is the only visible part of a 300,000-light-year-long streamer of gas stretching around the galaxy, called IC 2947. It’s the size of our Milky Way galaxy, and its bright green color is caused by glowing oxygen.
It’s visible courtesy of a beam of light from the galaxy’s core, which is illuminating it in rather the same way as a beam of sunlight lights up dust in the air. But this beam comes from a quasar – a bright, energetic object powered by a black hole – which may actually have turned off about 200,000 years ago.
Providing a rather pretty color combination is the yellowish-orange area at the tip of Hanny’s Voorwerp, which is a pocket of star clusters covering an area a few thousand light- years wide. The youngest stars are a couple of million years old.
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 – all suggesting the aftermath of a galaxy merger.
The image was made by combining data from the Advanced Camera for Surveys and the Wide Field Camera 3.