Located half a billion light-years from Earth, ESO 306-17, is a large, bright elliptical galaxy in the southern sky of a type known as a fossil group.

Astronomers use this term to emphasize the isolated nature of these galaxies. However, are they like fossils - the last remnants of a once active community - or is it more sinister than that? Did ESO 306-17 gobble up its next-door neighbors?

In this image, taken by the Advanced Camera for Surveys aboard Hubble in November 2008, it appears that ESO 306-17 is surrounded by other galaxies, but the bright galaxies at bottom left are thought to be in the foreground, not at the same distance in the sky. In reality, ESO 306-17 lies fairly abandoned in an enormous sea of dark matter and hot gas.

When zooming in closely on ESO 306-17, one can see faint clusters of stars through the bright shine of the galaxy's large halo. These are globular clusters - tightly bound groups of stars that can often fend off cannibalism from larger, "bully" galaxies. Studying these surrounding clusters will prove helpful to astronomers in their pursuit to put the pieces of ESO 306-17's history together.

"This image from the Advanced Camera for Surveys aboard the NASA/ESA Hubble Space Telescope highlights the large and bright elliptical galaxy called ESO 306-17 in the southern sky. In this image, it appears that ESO 306-17 is surrounded by other galaxies but the bright galaxies at bottom left are thought to be in the foreground, not at the same distance in the sky. In reality, ESO 306-17 lies fairly abandoned in an enormous sea of dark matter and hot gas. (Credit: NASA, ESA and Michael West (ESO))"

Source: ESA