Hubble stumbles across galaxies up to 10 billion light years distant

December 02, 1992|By Douglas Birch | Douglas Birch,Staff Writer

WASHINGTON -- Astronomers using the Hubble Space Telescope say they accidentally found what may be the oldest, faintest and most distant cluster of galaxies ever glimpsed -- a lumpy arc of perhaps a half-dozen small star groups up to 10 billion light years away.

Because light began traveling from the cluster 10 billion years ago, astronomers say the Hubble photograph may have lifted the veil on a corner of the universe when it was just one-third its present age, an estimated 15 billion years.

"It's like we are truly in a time machine with the Hubble," said Daniel W. Weedman, a professor of astronomy at Pennsylvania State University in University Park. Stephen P. Maran, an astronomer at Goddard Space Flight Center in Greenbelt called the latest Hubble image "mind-bending."

Alan Dressler, an astronomer with the Observatories of the Carnegie Institution in Pasadena, Calif., said he and his team of scientists were not searching for the primordial galaxies.

Six months ago, they aimed the orbiting telescope at a huge galaxy cluster, discovered in the 1940s by astronomer George Abell and known as Abell 851. The cluster, which astronomer Bruce Margon of the University of Washington in Seattle called a churning "cosmic Cuisinart," is perhaps 4 billion light years away.

The resulting photograph, a six-hour exposure spread over 10 of Hubble's orbits of the Earth, provided Dr. Dressler's team with a highly-detailed picture, and what they called the first atlas of galaxies that distant and that old. It sharply distinguishes their various shapes and even depicts galaxies colliding or sideswiping one another.

The Abell 851 galaxy cluster has been photographed by ground-based telescopes, said Dr. Margon.

"But they each looked like little teeny smudges of light," he said. jTC "Never before have we had the ability to classify the shapes of galaxies at these tremendous distances."

The image also provided direct evidence that the universe is evolving, because certain galaxy shapes seem to have been more common 4 billion years ago -- a time when astronomers think our own sun and planets were starting to swirl together out of cosmic dust and gas.

"It's one of the best pieces of evidence that the universe evolves . . . and on pretty rapid time scales," Dr. Dressler said.

Even as Dr. Dressler and his team pored over the galaxies in the photo's foreground, they found themselves distracted by what he described as "a lot of big fuzzy blobs" in the background.

This string of objects seemed to be strung out near a quasar -- an enor

mously powerful object as bright as a trillion suns -- known to be 10 billion light years away. (A light year is about 6 trillion miles.)

"We found this interloper," Dr. Dressler said. "It was really more of a nuisance than anything else."

But the astronomers were struck by "how small and how different these things looked," he said. Finally, they decided the blobs were either small galaxies, only a few thousand light years across, or white-hot areas where stars were being formed within larger structures too faint to be seen.

With the Hubble's flawed vision, he said, there's no way to tell. "We'll have to see a deeper image," he said. "And we'll have to wait until the Hubble is fixed to do it."

After the $2 billion Hubble was launched in April 1990, it was discovered that its nearly 8-foot-wide main mirror was misground. NASA plans to try to install corrective optics in the telescope during a December 1993 Space Shuttle mission.

Either way, he said, "I've never seen anything like this."

Spectroscopic measurements are needed to confirm that the objects are really 10 billion light years away -- a job that Hubble isn't suited for. That, Dr. Dressler said, "is going to take the very best, biggest telescopes we have on Earth."

Galaxies are churning clouds of hundreds of billions of stars. These cosmic creatures move in small packs, called groups, and in huge herds, called clusters or superclusters, across the cosmic tundra.

They come in three basic shapes: ellipticals, which can be round like a basketball or oblong like a football; spirals, long-armed objects that resemble hurricanes viewed from above; and irregulars, which are tugged like taffy into indeterminate shapes.

Our Milky Way galaxy -- in which the sun is just one of 200 billion stars -- is a spiral.

The Hubble photograph of Abell 851, Dr. Dressler said, provides evidence that spirals, rare in younger and closer galaxy groups, made up almost a third of the galaxies in the cosmos 4 billion years ago.

Hervey S. Stockman Jr., deputy director of the Space Telescope Science Institute, said the Abell 851 observation is the beginning of some of the telescope's most important work.

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