September 13, 2005 in Nation/World

NASA satellite detects most distant star

John Johnson Jr. Los Angeles Times

In the equivalent of spotting a bonfire at the dawn of time, NASA’s orbiting Swift satellite has recorded the most distant exploding star – a cosmic conflagration that took place a mere 500 million years after the creation of the universe.

Located 12.6 billion light years from Earth, the explosion shows giant stars formed earlier than thought.

“This is the first direct evidence of very early stars,” said Neil Gehrels of the Goddard Space Flight Center in Maryland. “It tells us when the dark ages of the early universe were coming to an end.”

The dark ages refers to the time when the cosmos went black a few hundred million years after the Big Bang flooded the universe with light and matter. The dark ages lasted a few hundred million more years until stars began to form, relighting the universe.

“For the first time we can learn about individual stars from near the beginning of time,” said Gehrels, principal Swift mission investigator. “There are surely many more out there.”

The National Aeronautics and Space Administration launched Swift a year ago to detect the gamma ray bursts from explosions of massive stars. The most powerful explosions in the universe, the bursts are essentially the birth cries of black holes. Black holes form out of the remains of collapsed stars and are so dense not even light can escape their grasp.

It’s thought that a gamma ray burst occurs somewhere in the universe virtually every day. Yet because the bursts last, at most, for a few dozen seconds, detecting them as they happened was impossible before Swift.

As its name implies, Swift was designed to pivot rapidly in space so emanations from the exploding star, from light waves to X-rays, could be captured before the explosion died away.

In this case, Swift picked up the first evidence of an explosion lasting 200 seconds on Sept. 4. The satellite relayed word to ground-based astronomers, who confirmed the finding by tuning in to the afterglow of the burst, which can last as long as several days.

“I’m so thrilled that Swift has made this possible,” said Don Lamb of the University of Chicago. “It’s wonderful to have the premier scientific objective of the mission come to fruition less than a year after launch.”

Lamb had predicted in 1999 that massive stars would exist in this ancient region of the universe, even though some scientists had speculated that it was too soon after the formation of stars for a massive star to grow and then self-destruct.

The explosion occurred when the universe was about 7 percent of its current age of 13.7 billion years.

“We designed Swift to look for faint bursts coming from the edge of the universe,” Gehrels said. “Now we’ve got one and it’s fascinating.”

Only one quasar has been discovered farther away than the gamma ray burst. Quasars are huge black holes containing the mass of billions of stars. This latest burst is unique because it came from a single star.

“This is uncharted territory,” said Daniel Reichart, an astronomer at the University of North Carolina at Chapel Hill. “This burst smashes the old distance record by 500 million light years. We are finally starting to see the remnants of some of the oldest objects in the universe.”

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