Hickson 91 in Piscis Austrinus.

Scanning the skies for galaxies, Canadian astronomer Paul Hickson and colleagues identified some 100 compact groups of galaxies , now appropriately called Hickson Compact Groups (HCGs). This sharp telescopic image captures one such galaxy group , HCG 91, in beautiful detail. The group's three colorful spiral galaxies at the center of the field of view are locked in a gravitational tug of war , their interactions producing faint but visible tidal tails over 100,000 light-years long. Their close encounters trigger furious star formation . On a cosmic timescale the result will be a merger into a large single galaxy, a process now understood to be a normal part of the evolution of galaxies, including our own Milky Way . HCG 91 lies about 320 million light-years away in the constellation Piscis Austrinus . But the impressively deep image also catches evidence of fainter tidal tails and galaxy interactions close to 2 billion light-years distant.