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Star Formation May Have Occured Earlier, Quicker Than Previously Believed - 2002-01-09


The deepest views of the universe ever taken have yielded clues that the dark cosmos lit up earlier and quicker than previously believed after its birth. New calculations by U.S. astronomers indicate that star formation began with an intense burst within only a few hundred million years of creation.

A new notion is challenging the view that star birth proceeded casually throughout the eons, peaking in intensity perhaps five to seven billion years after the so-called Big Bang before trailing off.

The interpretation is based on an analysis of Hubble Space Telescope images of more than 2,000 galaxies reaching almost to the edge of the universe, and therefore offering a glimpse of conditions near the beginning of time.

"Our results suggest that star formation in the universe took place early and rapidly," said State University of New York astronomer Ken Lanzetta. He concludes that the universe created a significant portion of its stars in a firestorm of star birth between just 500 million and one billion years after creation.

The rate of formation, he said, was 10 times the current rate of star birth. Mr. Lanzetta said, "Previous measurements have missed a dominant fraction of the light of the most distant galaxies. Our results indicate that the distant universe contained far more light and hence far more stars than was previously believed."

The results are not obvious from a casual view of the Hubble images. The most distant galaxies, those from which light is just getting to us from near the beginning of time, are extremely faint. They do not seem to support the idea that the early universe may have been busier than today.

But Mr. Lanzetta and his associates devised a technique for interpreting the images that suggests the visible light reaching us is just 10 percent of what was really shining at the time. He said, "As we go to larger and larger distances, that is, back to earlier and earlier times, we realize that we can see only the very brightest regions of the galaxies. We don't see those intermediate regions and we don't see those faint regions. So we have to somehow indirectly infer or argue based on different lines of evidence to try to make up for the intermediate and faint regions of galaxies."

To get at an answer, the Lanzetta team made a three dimensional galaxy map from Hubble's two-dimensional images based on the color of the galaxies, which indicate distance. Then the astronomers assumed that the oldest, farthest galaxies had the same amount of light distribution within them as closer, newer ones do.

The associate director of the Baltimore institute that operates the Hubble telescope, Bruce Margon, says Mr. Lanzetta has teased out incredibly subtle information from tiny, fuzzy images. "Why do we care," Mr. Margon asked? "The point is, star formation didn't necessarily have to occur in a huge burst immediately after the Big Bang. It is not at all intuitively what one might have predicted, that this great burst of star formation was at the beginning rather than the end of the universe."

The findings are curtain to be controversial, and Mr. Lanzetta says there is only one sure proof. "When we actually see the missing light, then, of course, we'll know that this is definitely correct," he said. "It's unlikely that with the current generation of telescopes we will be able to see that missing light."

Mr. Lanzetta will try to directly observe a portion of that light with an advanced camera U.S. astronauts are to install on the Hubble telescope next month that will be able peer even deeper in the universe.

The U.S. space agency, NASA, is also planning to launch a successor to Hubble in 2009 with the main goal of actually seeing the universe's first light.

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