The most distant explosion ever recorded, signaling the birth of a black hole near the beginning of time, was more chaotic and lasted longer than astronomers would have expected.
The event was first reported last fall. Today scientists released new findings and an animation that depicts a strange sequence of events in which the explosion of a massive star first settles down but then fires back up several times toward the end.
Astronomers speculate that the black hole did not form instantly, as theory predicts, but that it was a prolonged process.
"This was a massive star that lived fast and died young," said David Burrows, a professor of astronomy and astrophysics at Penn State and author of one of three papers in the March 9 issue of the journal Nature.
The burst, named GRB 050904, originated 12.8 billion light-years away, which means it occurred 12.8 billion years ago and the light took that long to reach us. It erupted very nearly at the beginning of time-the universe is about 13.7 billion years old.
The event provides the first glimpse of a star when the universe was in its infant stages. Until now, only entire galaxies had been observed so far away.
"Because the burst was brighter than a billion suns, many telescopes could study it even from such a huge distance," Burrows said.
The event was initially noted by NASA's orbiting Swift observatory as a gamma-ray burst that lasted more than 8 minutes. That burst of high-energy radiation was followed by afterglows in visible light and other wavelengths on the electromagnetic spectrum. Researchers have been examining the data ever since.
Astronomers know very little about the stars that formed back then, other than the presumption that they were made almost entirely of hydrogen and helium and a trace of lithium; other, heavier elements formed only when the first stars exploded.
Astronomers did find hints of heavier elements in GRB 050904, report a Japanese group led by Nobuyuki Kawai at the Tokyo Institute of Technology.
"We designed Swift to look for faint bursts coming from the edge of the universe," said Neil Gehrels of NASA Goddard Space Flight Center and Swift's principal investigator. "Now we've got one and it's fascinating. For the first time we can learn about individual stars from near the beginning of time. There are surely many more out there."
The flaring of GRB 050904 is something not typically seen in closer bursts. That means the earliest black holes might have formed differently than those being born today, Burrows said. The difference could be because the first stars were more massive, or perhaps it's just because the cosmic environment was different then.
In an analysis of the work, Enrico Ramirez-Ruiz of the Institute for Advanced Study in Princeton writes that the combined observations pave the way for the discovery of distant galaxies that are otherwise too dim to spot.
Gamma-ray bursts "will serve not only as signposts to such galaxies, but could be used to study the gradual build-up of heavy elements in them to determine the conversion history of primordial gas into stars, Ramirez-Ruiz writes. "And if bursts can be detected from a time before galaxies had gravitationally assembled, they might even provide a glimpse into the pregalactic phase of the universe."
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