Galaxies far and wide.

Galaxies far and wide

By carefully recording the faint light surrounding a bright galaxy at the center of a dense cluster, a team of astronomers has uncovered evidence for pherhaps the largest and most luminous galaxy known. This gigantic agglaomeration of stars, which sits at the center of a rich galaxy cluster called Abell 2029, extends 6 million light-years in diameter (more than 60 times the width of the Milky Way) and emits more than a quarter of all the light produced by the entire cluster. Juan M. Uson of the National Radio Astronomy Observatory in Socorro, N.M., and his colleagues describe their discovery in the Oct. 26 SCIENCE.

"The central galaxy in Abell 2029 is remarkable for its size as well as the uniformity of its structure," they report. "Both of these characteristics suggest that its birth must have occurred during the initial formation of the cluster."

At the same time, astronomers working at the European Southern Observatory's La Silla telescope in Chile have discovered the most distant "normal" galaxy known so far. Now designated G 0102-190, this galaxy, which resembls the Milky Way, is so far away that the lght detected by astronomers was emitted when the universe was only one-third as old as it is now. The galaxy appears surrounded by an extensive gaseous halo -- a feature not usually found around nearby, "normal" galaxies.

The astronomers identified the extremely faint galaxy by looking for characteristic changes in the light spectra emitted by distant quasars. The gas in any galaxy that happens to fall on the same line of sight as a quasar would absorb certain wavelengths of light, allowing astronomers to estimate the distance to the intervening galaxy. The discovery of G 0102-190 provides valuable clues about the formation and evolution of galaxies in the early universe.