[Paleopsych] Space.com: Creation of Black Hole Detected
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Thu May 12 19:21:14 UTC 2005
Creation of Black Hole Detected
By Robert Roy Britt
Senior Science Writer
Astronomers photographed a cosmic event this morning which they
believe is the birth of a black hole, SPACE.com has learned.
A faint visible-light flash moments after a high-energy gamma-ray
burst likely heralds the merger of two dense neutron stars to
create a relatively low-mass black hole, said Neil Gehrels of NASA's
Goddard Space Flight Center. It is the first time an optical
counterpart to a very short-duration gamma-ray burst has ever been
Gamma rays are the most energetic form of radiation on the
electromagnetic spectrum, which also includes X-rays, light and radio
The merger occurred 2.2 billion light-years away, so it actually took
place 2.2 billion years ago and the light just reached Earth this
Quick global effort
Gehrels said the burst occurred just after midnight East Coast time.
It was detected by NASA's orbiting Swift telescope. Swift
automatically repositioned itself within 50 seconds to image the same
patch of sky in X-rays. It just barely caught an X-ray afterglow,
Gehrels said in a telephone interview.
The X-ray counterpart was barely detectable and only observed for a
An email was sent out to astronomers worldwide, and large
observatories then tracked to the location and spotted a faint
Gamma ray bursts are mysterious beasts. They come from all over
the universe. Long-duration bursts, lasting a few seconds, are thought
to be associated with the formation of black holes when massive stars
explode and collapse. In recent years, scientists have detected X-ray
and optical afterglows of these long bursts.
Very short-duration bursts, like the one this morning, last only a
tiny fraction a second. Until now, no optical afterglows from these
bursts have been detected. Theorists think a burst like this
represents the formation of a black hole a few times the mass of the
Sun, but if so, then there should be flashes of X-rays and visible
The burst has been named GRB050509b.
Steinn Sigurdsson, a Penn State University researcher who is excited
about the observations but was not involved in them, explained what
theorists think happened:
Over a long time period, at least a hundred million years and perhaps
billions of years, the two neutron stars spiraled toward each other.
Neutron stars themselves are very dense objects, collapsed stellar
"A fraction of a second before contact, the lower mass neutron star is
disrupted and forms a neutrino driven accretion disk around the higher
mass neutron star," Sigurdsson told SPACE.com. "It implodes under the
weight and forms a maximally spinning low-mass black hole."
Astronomers can't see black holes, because light and everything else
that enters them is lost to observation. But just before material
falls in, some high-energy process -- likely involving magnetism and
speeds approach that of light -- vents some of the material back into
The gamma ray burst signals the formation of a superheated jet of gas
being shot out from the chaotic region around the newly formed black
hole at a significant fraction of light-speed, Sigurdsson said.
"This really does look like a merger scenario," said Gehrels, who
heads up the scientific operations for the Swift satellite.
The first gamma-ray burst was detected by accident in 1967. It was
found by U.S. satellites deployed to monitor possible violations of
the nuclear test ban treaty. Researchers now know that one erupts
roughly every day somewhere in the cosmos. Most originate many
billions of light years away.
Each burst can briefly outshine an entire galaxy. Gamma-ray bursts in
our own galaxy are very rare. Some scientists speculate that such
bursts in the Milky Way's past might have caused mass extinctions
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