SETI public: Cosmic flashes solved - Scientists say explosions are from dying star

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The original article can be found on SFGate.com here:

http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2003/09/12/MN285528.DTL

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Friday, September 12, 2003 (SF Chronicle)

Cosmic flashes solved/Scientists say explosions are from dying stars two galaxies away

David Perlman, Chronicle Science Editor

   Mysterious X-ray flashes in distant space that have puzzled astronomers
for years have been identified by scientists at Caltech and Harvard as
cosmic explosions from dying stars in two galaxies some 2.6 billion
light-years away.

   The stars that die in monstrous blasts brighter than 10 billion suns are
known as supernovae, and the powerful gamma ray bursts they emit were only
located and identified last year after a 30-year quest.

   But the X-ray flashes that have been seen for the past three years
remained a puzzle until astronomers gathered data on them from telescopes
atop Palomar Mountain in Southern California; from giant radio telescopes
in New Mexico known as the Very Large Array; and from an armada of
satellites, including NASA's Chandra X-ray observatory and another called
the High Energy Transient Explorer, or HETE, which is run by an
international group of astronomers from the United States and seven other
nations.

   At an international conference at Los Alamos Thursday, the scientists
reported they had determined the source of the X-ray flashes and said the
strange phenomena have now "joined the family of energetic cosmic
explosions" that have given astronomers new insights into the nature of
supernovae, black holes and the expansion of the universe.

   According to Shri Kulkarni, professor of astronomy and planetary sciences
at the California Institute of Technology, it was his own graduate
student, Alicia Soderberg of Mashpee, Mass., who analyzed signals from the
High Energy Transient Explorer satellite that detected a fading X-ray
afterglow coming from a distant explosion similar to other exploding stars
that emit more energetic gamma ray bursts.

   Soderberg used Caltech's 200-inch Palomar telescope to determine the
distance and location of the faint flashes -- an accomplishment that she
said left her so excited she "could not sleep for three days."

   X-ray flashes are relatively rare compared with other signals from objects
bursting in space. A Harvard team of astronomers headed by Joshua Bloom of
the Harvard-Smithsonian Center for Astrophysics also located another group
of the flashes. Bloom said they were identified in two so-called 'blue
galaxies," where stars by the millions are constantly being formed.

   But in those same galaxies that harbor stellar newborns, some of the more
massive stars are known to explode, and it was from one of those
explosions that the Harvard group detected the burst of X-ray flashes.

   Pinpointing the location of the X-ray flashes in galaxies only a few
billion light years away effectively ends one major controversy in
astrophysics, Bloom noted.

   Some scientists had speculated that the flashes were "the death cries from
stars exploding in the infant universe," as Bloom put it.

   That idea would mean that the new universe, some time after the Big Bang
nearly 14 billion years ago, already held stars old enough to have died in
catastrophic explosions emitting both gamma rays and X-rays. But now that
the X-ray flashes are known to come from stars in galaxies less than 3
billion years old, the idea of stellar explosions in an "infant" universe
no longer holds up, Bloom said.

   E-mail David Perlman at dperlman@sfchronicle.com.

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