Saturday, February 5, 2011

Distant galaxy may be oldest ever seen

Astronomers said this week that they found a distant galaxy that could be the oldest object ever observed in the universe.

The discovery could help them understand the early days after the Big Bang - a time more than 13 billion years ago when the first stars were born.

But some scientists were more intrigued by the vast emptiness that apparently surrounds the ancient galaxy.

"The most interesting thing is the galaxies they didn't detect," said Mark Dickinson, an astronomer at the National Optical Astronomy Observatory in Tucson who wasn't involved in the discovery.

The galaxy, known as UDFj-39546284, was spotted in a patch of sky called the Hubble Ultra Deep Field. Based on their understanding of how the universe evolved, the scientists who scoured that region had expected to find about five galaxies that were roughly the same age. But they saw only one.

"That told us very dramatic things are happening with galaxy generation" at that time, said University of California-Santa Cruz, professor Garth Illingworth, a member of the research team that published its findings Thursday in the journal Nature.

"We're getting close to the era of galaxy birth."

The galaxy in question is quite small, with a mass less than 1 percent that of our Milky Way.

It is also gassy and comprised of "fuzzy bright blue blobs of tens of millions of stars," Illingworth said.

If the team's estimates of its age are correct, the galaxy's redshift - a measure of how fast the galaxy and the Earth are moving away from each other due to the expansion of the universe - is around 10.

That means it existed a mere 480 million years after the Big Bang, when the universe was just 4 percent of its current age.

The earliest galaxies previously identified have redshifts of around 8.5. They emitted their light about 100 million to 150 million years later than UDFj-39546284.

Experts caution that they can't be certain UDFj-39546284 is indeed as old as the team suspects until the light it emits can be analyzed more precisely with a spectrograph.

by Eryn Brown Los Angeles Times Jan. 29, 2011 12:00 AM

Distant galaxy may be oldest ever seen

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