Most Distant Galaxy Pile-Up Found

April 4, 2008 -- Astronomers have announced the discovery of the most distant galactic collisions ever seen: a cluster of early galaxies caught in the act of merging into one giant galaxy when the universe was just a toddler.

The galactic "proto-cluster," named LBG-2377, is a whopping 11.4 billion light-years away and in the past. It provides a window into a time well after the universe inflated and spread matter far and wide, but still at a time when all of that matter was coalescing to make the clusters and super-clusters of galaxies that collectively create the cob-webby structure of matter in the modern universe.

Using the volcano-top Keck Telescope in Hawaii, the team captured the image of the galaxies in the act of coming together at about two billion years after the Big Bang. The discovery was originally part of a broader survey of distant galaxies.

"This particular system showed up as a particularly bright one," said Jeff Cooke, a postdoctoral researcher at the University of California at Irvine (UCI). Cooke and his colleagues published their discovery in online astrophysics bulletin astro-ph.

In order to be so bright at such a distance, LBG-2377 must be about 10 times the mass of the Milky Way, say the researchers. The number of galaxies involved in the merger was gleaned from LBG-2377's spectra of light, which contain multiple galactic signals.

Equally important is the fact that the galaxies have been caught in the act of firing up loads of young stars that are very bright in ultraviolet light.

"It wasn't at all what I expected," Cooke told Discovery News. "The event is so violent and catastrophic and they are creating so many new stars" that it shines far brighter than any other galaxies or clusters of galaxies at such a distance. "It's definitely the farthest merging galaxy cluster."