Astronomers Push Back Most Prolific Star-Forming Era — Maybe
(From the March/April 2002 issue of StarDate magazine)
Researchers delving into the deepest images ever taken say that their research puts the most prolific, violent era of star formation in the first few hundred million years after the Big Bang, instead of four billion years after it, as astronomers thought. In essence, “The finale came first,” said Kenneth N. Lanzetta, of the State University of New York at Stony Brook. Lanzetta presented his research at a January news conference at NASA Headquarters in Washington, D.C.
“If this can be verified, it will dramatically change our view of the universe,” said Anne Kinney, director of the Astronomy and Physics Division at NASA Headquarters. “Because stars are the building blocks of galaxies and the birthplace of solar systems, proving that countless numbers of stars began forming so early after the birth of the universe could cause us to rethink a lot of our theories.”
Lanzetta and colleagues reached their conclusions by studying the light from thousands of galaxies discovered in the three Hubble Deep Field images, made in 1995 and 1998 by the Hubble Space Telescope. For several years, astronomers all over the world have been attempting to measure distances to these galaxies, by using the world’s largest ground-based telescopes to measure their spectra. But so far, only 150 distances have been measured in this traditional way.
Lanzetta’s group used a different method: they looked at the galaxies’ colors. As the universe expands, photons lose energy and become redder. The most distant galaxies are the reddest. Lanzetta used this relationship to find distances to 5,000 galaxies in the Deep Field images.
No matter how bright a galaxy is, it will appear dimmer the farther it resides from us. “Distant galaxies are so distant that they look faint, but intrinsically, they aren’t,” Lanzetta said. “HST reveals the tip of the iceberg, but misses the iceberg. . . .There is missing light in these images.” But if astronomers measure a galaxy’s apparent brightness and its distance, they can deduce its true luminosity.
“The distant [and thus, earlier] universe contained far more light than we ever thought,” Lanzetta said. His research showed that the farther away galaxies are, the brighter they are. This light came from star formation, which leads to the conclusion that a burst of star formation occurred soon after the Big Bang.
According to Bruce Margon, an astronomer at the Space Telescope Science Institute in Baltimore, Lanzetta’s result “will be controversial, because he’s teasing out a very subtle effect from things far too distant to take spectra of with any existing telescope.” But Margon predicted that “[future] six-meter class telescopes in orbit will show the very earliest galaxies lit up and riddled with these violent bursts of star formation.”
Lanzetta’s work is scheduled for publication in an upcoming issue of The Astrophysical Journal. — Rebecca Johnson
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