UH astronomers see earliest galaxies
POSTED: Sunday, June 14, 2009
University of Hawaii astronomers and colleagues have observed the first galaxies formed shortly after the universe began with the Big Bang 13.7 billion years ago.
"The light from these galaxies was already more than halfway along on its journey before the Earth and the sun had been formed," Alan Stockton of the UH Institute for Astronomy said in an e-mail. "These, then, were among the very first massive galaxies to form in the universe."
The galaxies are at distances with light-travel times of about 11 billion years, so they are being observed when the universe was about 2.7 billion years old, he said.
Though the galaxies in the early universe are much smaller than those in the Earth's neighborhood, he said, they have similar numbers of stars.
"In the most extreme cases, including one we have studied, some of these galaxies pack all of the stars of a fairly massive present-day galaxy in a volume about 1,000 times smaller," Stockton said.
Stockton reported the findings of his group, including astronomers at the University of California-Riverside and Santa Cruz, at the American Astronomical Society meeting last week in Pasadena, Calif.
The astronomers are using the laser-guide-star adaptive-optics system of the 400-inch Keck II Telescope on Mauna Kea for their observations.
An interesting question, Stockton said, is why similar objects aren't seen now.
"In some form or other, they must be represented among the most massive galaxies that we see around us. It is likely that many have merged with other galaxies or have otherwise acquired surrounding, more diffuse envelopes of stars, but such processes probably are not sufficient.
"It may be that the star density in the central region of some of these galaxies is so high that interaction between stars leads to a redistribution of orbits, puffing up the outer parts of the galaxy," he suggested, "while the inner region becomes even denser, perhaps finally collapsing into one of the supermassive black holes that seem to be ubiquitous in the centers of present-day massive galaxies."