wacki
04-12-2005, 03:42 AM
http://www.guardian.co.uk/uk_news/story/0,3604,1456594,00.html
A huge blast of radiation from an exploding star might have been behind one of the Earth's worst mass extinctions, some 450m years ago.
...........
Gamma ray bursts are thought to be caused either when two neutron stars collide or when giant stars collapse into black holes at the end of their lives.
For around 10 seconds, intense pulses of energy are fired off, which can be detected right across the universe. All the bursts recorded by astronomers so far have come from distant galaxies and are therefore harmless to the Earth.
But if a burst occurred in our own galaxy, the effect would be devastating.
Dr Adrian Melott, of the University of Kansas and an author of the latest paper, said: "A gamma ray burst originating within 6,000 light years from Earth would have a devastating effect on life.
"We don't know exactly when one came, but we're rather sure it did come - and left its mark."
Such a burst would strip the Earth of its protective ozone layer, allowing deadly ultraviolet radiation to pour down from the sun.
Computer models showed that up to half the ozone layer could be destroyed within weeks. Five years later, at least 10% would still be missing.
Sounds like fun. /images/graemlins/grin.gif
A huge blast of radiation from an exploding star might have been behind one of the Earth's worst mass extinctions, some 450m years ago.
...........
Gamma ray bursts are thought to be caused either when two neutron stars collide or when giant stars collapse into black holes at the end of their lives.
For around 10 seconds, intense pulses of energy are fired off, which can be detected right across the universe. All the bursts recorded by astronomers so far have come from distant galaxies and are therefore harmless to the Earth.
But if a burst occurred in our own galaxy, the effect would be devastating.
Dr Adrian Melott, of the University of Kansas and an author of the latest paper, said: "A gamma ray burst originating within 6,000 light years from Earth would have a devastating effect on life.
"We don't know exactly when one came, but we're rather sure it did come - and left its mark."
Such a burst would strip the Earth of its protective ozone layer, allowing deadly ultraviolet radiation to pour down from the sun.
Computer models showed that up to half the ozone layer could be destroyed within weeks. Five years later, at least 10% would still be missing.
Sounds like fun. /images/graemlins/grin.gif