Some dying
stars smolder into darkness while others quickly shed their coat of hot gases.
But some go out with a bang, propelling their remains through the cosmos at more
than 99.9997 percent of the speed of light--the maximum speed limit in the
universe.
Using a
robotic telescope at the European Space Organization's La Silla Observatory in Chile, called the Rapid Eye Mount (REM) telescope, astronomers have measured
once-theoretical speeds of the explosions known as gamma-ray bursts for
the first time.
"This is
very exciting," said Stan Woosley, an University of California astronomer and
astrophysicist who was not involved in the research. Woosley said the energy
found in the bursts "strain the models" dictating how fast
matter can go.
The
findings are detailed in the latest issue of the journal Astronomy &
Astrophysics.
Rapid
observations
The bursts
last only seconds to several minutes and their intense energy is at very short wavelengths
we can't see, so timing and an automated recording method is critical in order
to catch one.
Emilio
Molinari, an astronomer with the Brera Astronomical Observatory in Italy and co-author of the study, said the observation was possible thanks to quick,
automated observations of major galactic catastrophes.
"We can now
study in great detail the very first moments following these cosmic
catastrophes," Molinari said.
In two
separate events, on April 18 and June 7 of last year, NASA's Swift
satellite detected a bright gamma-ray burst and automatically notified the
small REM telescope. Just 40 seconds after each explosion, the robotic observer
swung around and aimed its lens at the event. Although the initial explosions
were invisible at first, the intense energy heated up nearby gas which could be
seen in near-infrared light by the telescope.
Warp
speed
By studying
the changing brightness of both bursts, the astronomers
measured how fast matter was careening away from the bursts. Astrophysicists use
a special system to peg the speed of matter, called the Lorentz factor--the
higher the number, the closer to the speed of
light.
In the case
of both bursts, the Lorentz factor was 400--an unprecedented observation until
now.
Stefano
Covino, another co-author of the study and astronomer at the Brera Astronomical
Observatory, said the speed wasn't the only impressing figure.
"While
single particles ... can be accelerated to still larger velocities, the present
cases are the equivalent of about 200 times the mass of the Earth acquiring
this incredible speed," Covino said.
"You
certainly wouldn't like to be in the way," said Susanna Vergani, another
team member.
Now that
the team has made the striking observations, they are trying to find some way
to explain them. "The next question is which kind of 'engine' can
accelerate matter to such enormous speeds," Covino said.
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