Boffins fear killer gamma death blasts from space

Boffins have discovered that short hard bursts of radiation in space caused by colliding stars could be as dangerous to the world's atmosphere as longer, high-energy ones.

Studies have already shown that long bursts of gamma radiation from space, such as those caused by supernovae and extreme solar flares, can punch holes in the ozone layer, letting powerful and damaging amounts of ultraviolet radiation through to the Earth's surface.

But astrophysicists at Washburn University in Colorado have now found that short discharges are "probably more significant", even though they usually last for less than a second.

"The duration is not as important as the amount of radiation," said Brian Thomas, who will be presenting the findings at the annual general meeting of the The Geological Society of America on Sunday. "What I focused on was the longer term effects."

The short radiation blasts are thought to be caused by the collision of two neutron stars or even black holes careening into each other, and if such an event happened inside the Milky Way, the results could be devastating to the Earth's surface and oceans.

The main consequence of the blast would be to deplete the ozone layer, which would wreck the planet. The radiation surge would knock oxygen and nitrogen atoms out of stability, which would then recombine as nitrous oxide and hang around doing more damage until they were rained out.

Based on observations of other galaxies, these short hard bursts take place about once every 100 million years, but it is very difficult to tell when Earth has been struck by them.

Any evidence that may have been left in space is long gone, so researchers need to look for evidence in the rocks here on the planet to try to establish when events may have taken place, and if they correlate to planetary extinctions.

"I work with some paleontologists and we try to look for correlations with extinctions, but they are skeptical," said Thomas. "So if you go and give a talk to paleontologists, they are not quite into it. But to astrophysicists, it seems pretty plausible." ®