You can remove one potential threat from your worry list,
based on new observations by the Hubble Space Telescope.
The observatory has been used to study long-duration
gamma-ray bursts, which are powerful flashes of high-energy radiation that
emanate from some exploding stars. Astronomers have said before that if one of
these flared up in our neck of the woods, Earth would be toasted and much of
life could be destroyed.
But it is unlikely one of these bursts will occur in our
Milky Way Galaxy, the new study finds.
The study, detailed in the May 11 issue of the journal
Nature, confirms similar work done with other telescopes and reported
last month.
Long-duration gamma-ray bursts (those lasting more than a
couple seconds) are related to the deaths of huge stars, those at least 20
times as massive as our Sun and which are low on heavy elements.
Such stars are uncommon in our galaxy. They were prevalent
when the universe was young, before multiple generations of stars created the
heavier elements such as carbon and oxygen that are common to our galaxy. The
Hubble study found the events tend to emanate from small, irregularly shaped
galaxies--those seen to exist before mergers had created the larger galaxies
seen in the nearby cosmos.
The upshot: Long-duration gamma-ray bursts tend to come from
very, very far away, which in cosmic terms means they occurred long, long ago
and the radiation is just reaching us after billions of years of traversing the
universe.
Of 42 bursts studied, only one came from a large spiral
galaxy like the Milky Way.
Modern massive stars, which are abundant in heavier
elements, are unlikely to trigger long-duration gamma-ray bursts, also called
GRBs, the researchers explain. By the time they explode as supernovas, these
stars have already lost significant material through long-term outflows called
stellar winds. There is not enough mass left to create a burst when they go
supernova.
"It's a Goldilocks scenario," explained study leader Andrew
Fruchter of the Space Telescope Science Institute. "Only supernovae whose
progenitor stars have lost some, but not too much, mass appear to be candidates
for the formation of GRBs."
Short-duration gamma-ray bursts, lasting less then two
seconds and sometimes just milliseconds, can occur in our galaxy. Collisions
between neutron stars can create them, for example. They are 100 to 1,000 times
less powerful, however.
More
on the Risks of GRBs
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