Strange Galaxy Is a Beautiful Wimp

This new Hubble photo reveals a strange galaxy in a far off cluster of galaxies called the Coma cluster.

The galaxy, NGC 4921, is unusual because of its light, wispy swirls. These aren't as distinguished and bright as the spiral arms in most spiral galaxies, which are powered by the active creation of new stars. This weak-limbed galaxy belongs to a class called "anemic spirals," named for their wimpy arms and weak star formation.

The Coma Cluster, also known as Abell 1656, lies about 320 million light-years away from Earth in the northern constellation of Coma Berenices, the hair of Queen Berenice. More than 1,000 galaxies comprise the cluster. In the image, the ghostly NGC 4921 lies in a field of thousands of galaxies of all shapes, sizes and colors, many of which are much more remote than the cluster and stretch back toward the early universe.

Spiral galaxies are the minority in clusters like Coma, which are so packed that galaxies undergo frequent interactions and collisions. Over time, all this chaos distorts pristine spiral galaxies, with their distinct swirling arms, into mash-up egg-shaped ellipticals.

A research team lead by Ken Cook of the Lawrence Livermore National Laboratory in California used the Hubble Space Telescope's Advanced Camera for Surveys to take the photographs used to make this image. The picture we see is a combination of 50 separate exposures through a yellow filter, totaling about 17 hours of exposure time, plus 30 exposures through a near-infrared filter taken over 10 hours.