The discovery of what is believed to be the largest and brightest galaxy ever observed, more than 60 times the size of the Milky Way, may yield clues to one of astronomy's great mysteries: What makes matter in the universe clump together?

Identified at the heart of a distant cluster of a thousand galaxies known as Abell 2029, shown below in a computer-enhanced photograph, the giant galaxy alone contains more than 100 trillion stars, compared to about 3 billion stars in the Milky Way, according to astronomers who reported the find in last Friday's issue of Science.

"If we talk about the galaxy and the halo {the diffused light around it}, then it is the largest object that we are aware of," said Jeffrey R. Kuhn of Michigan State University, a co-author of the study.

Kuhn and his colleagues, Juan M. Uson of the National Radio Astronomy Observatory and Stephen P. Boughn of Haverford College, detected the galaxy by piecing together a mosaic that combined 16 photographs taken by a 36-inch telescope at the Kitt Peak National Observatory in Arizona.

The properties of the supergalaxy -- its apparent density, luminosity and smoothness -- will be studied for insights into the forces that made it form. The dominant theory holds that invisible matter, which gives off no radiation and cannot be detected, helps to provide the gravitational forces that organize such immense structures.