Scientists find most distant galaxy

Hubble picks up image

discovery could give clues to how universe evolved

February 16, 2004|By Michael Stroh | Michael Stroh,SUN STAFF

Tapping the powerful Hubble Space Telescope and a rare quirk of cosmic physics, astronomers have discovered the most distant galaxy in the universe, a faint, record-setting smear of light that flared just 750 million years after the big bang.

If confirmed, astronomers said, the discovery could provide new clues to fundamental questions such as when stars first began to shine and how a few simple chemical building blocks in the early universe evolved into the dazzling gallery of objects we see today.

"My initial impression is: Wow!" said Harry Ferguson, an astronomer at the Space Telescope Science Institute in Baltimore who was not involved in the discovery. "It's spectacular to find a galaxy that distant."

The infant galaxy, yet to be named, was found nestled among a large galactic cluster known as Abell 2218. Richard Ellis, an astronomer at the California Institute of Technology and member of the discovery team, said the object is about 13 billion light-years away.

One light-year is the distance light travels in a year, about 5.8 trillion miles.

The galaxy, said Ellis, likely was among the first formed after the mysterious period astronomers refer to as the "Dark Ages," an epoch before the lights in the universe came on. "In human terms, the universe isn't even on its feet yet, it's a toddler," he said.

A paper describing the find will be published in The Astrophysical Journal.

Powerful scopes

Ferreting out so distant and dim an object is an extraordinary technical feat, astronomers said. To do it, Ellis and his team turned to two of the world's most powerful telescopes.

The astronomers discovered the object using Hubble's Advanced Camera for Surveys. Installed by shuttle astronauts in 2002, the $75 million instrument is one of the most sensitive light detectors available to astronomers. Even so, Ellis and his team had Hubble stare at the same patch of sky for 15 hours to capture enough light.

The astronomers also used the largest ground-based telescope, the W.M. Keck Telescope on Mauna Kea in Hawaii, to nail down the precise age of the newly discovered object.

After two consecutive nights of observing, they determined that the light began its journey toward Earth 750 million years after the birth of the universe.

Cosmic magnifier

But the astronomers said even the most powerful man-made telescopes weren't powerful enough to see the galaxy. Ellis and his team also took advantage of a rare cosmic quirk known as a gravitational lens that naturally magnifies light from distant objects.

First predicted by Albert Einstein, gravitational lenses are so rare that astronomers know of fewer than 30 in the universe. They arise when light emanating from a distant star is amplified by the gravitational field of a massive object in its path -- in this case, the galactic cluster Abell 2218.

The gravitational lens created by Abell 2218 made the light from the distant galaxy 25 times brighter, nudging it just within the limits of Hubble's sensitive camera.

In all, the newly found galaxy is less than one-tenth the size of our own, the Milky Way. Preliminary evidence also indicated it contains huge stars many times the size of the sun.

Scientists said that although it is important, a single infant galaxy won't provide enough clues to answer all their questions about the early universe. Also, it's unclear how much longer they'll be able to continue their quest.

The announcement of the find comes just a month after the National Aeronautics and Space Administration scrubbed the final space shuttle maintenance mission to the telescope. Without the 2006 tuneup, the telescope is not expected to survive until its scheduled retirement date in 2010.

"This is the kind of thing that you can only do with Hubble," said Narciso Benitez, a Johns Hopkins University astronomer involved in a separate hunt for early galaxies.

Responding to widespread criticism, NASA Administrator Sean O'Keefe agreed this month to subject the decision to outside review. But the scientific future of the telescope -- and the future hunt for the earliest galaxies -- remains hazy.

Added Ellis: "Hubble is not just about taking pretty pictures. We're really pushing back the frontiers and learning where we came from."

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