Saturday, March 9, 2002

University of Hawaii

UH astronomers peer
back to universe’s infancy

Star-Bulletin staff

A galaxy discovered by University of Hawaii astronomers and international colleagues is giving them a look at the early formation of galaxies and stars.

UH astronomer Esther Hu, who led the research, said the galaxy "is forming stars at a time speculated to be in the 'Dark Ages' of the universe when galaxies begin to 'turn on.'"

It's believed the universe began with the Big Bang about 16 billion years ago. As it expanded and cooled over the next half-billion years -- the so-called Dark Ages period -- the cold gas began to form the first galaxies, the scientists said.

Re-ionized light from the newly formed galaxies and quasars ended the Dark Ages.

A paper reporting discovery of the new galaxy will appear in the April 1 issue of the Astrophysical Journal Letters.

The astronomers used the Abell 370 cluster, 6 billion light-years away with a mass of several hundred galaxies at its core, to magnify light from a galaxy behind the cluster that is 15.5 billion light years away.

Len Cowie, UH astronomer who was on the research team, said it is important that the new object is a galaxy and not a quasar. "When the first galaxies form, it's like turning on lights to clear out a fog bank," he said.

"Quasars are really bright, though rare, so they can make large clear cavities around themselves, but the fact that light from the fainter but much more numerous galaxies is getting out means that a significant amount of early star formation has already taken place and much of the general fog has already dissipated."

The latest galaxy identified represents the universe at about 780 million years of age -- about 50 million years earlier than the most distant quasar known and 80 million years earlier than the suspected end of the Dark Ages.

The team's findings were made with the Keck 1 telescope and followed up with infrared images on the Subaru Telescope, both on Mauna Kea.

"You want to catch galaxies in their infancy and see how they develop," Hu said. "Scaling the age of the universe to a person's lifetime, we're showing you baby pictures. The last galaxy snapshot showed a toddler just past his fourth birthday. This one is 3 1/2."

She said this is good news for the Next Generation Space Telescope to be launched in the next decade, because "there should be plenty of these distant galaxies bright enough to observe, using a large telescope with good infrared detectors above the strong air-glow of our atmosphere."

UH Institute for Astronomy

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