Gamma Ray Bursts

A pair of astrophysicists studying gamma ray bursts has found that such events might play a much larger role in the existence of life on Earth and other planets than has been thought. In their paper published in the journal Physical Review Letters, Tsvi Piran with the Hebrew University in Israel and Raul Jimenez from the University of Barcelona in Spain, suggest that gamma ray bursts might be responsible for past extinctions on Earth, and for limiting the possibility of life on planets near the center of galaxies. A gamma ray burst (GRB) is a massive wave of radiation that comes about very quickly due either from a star that is dying or when two neutron stars collide. When the wave strikes another planet it can cause major disruptions.

GRBs come in two varieties, long and short burst. The longer variety are much more common but until recently scientists didn't believe they could occur in our part of the universe at all because it was thought they only occurred in low low-metallicity galaxies. More recently it has been found that though more rare, they do also occur in high-metallicity galaxies like ours. Such findings led the researchers with this new effort to wonder what impact GRBs might have had, or continue to have, on the existence of life on planets, including ours.

Among other things, they found that based on the likely average incidence of GRBs happening close enough, calculations showed a 60 percent likelihood that a GRB has caused an extinction event here on Earth within just the past billion years. The researchers don't believe a GRB striking the Earth could penetrate the atmosphere, but do believe one could destroy the ozone layer, which would of course lead to the extinction of most living things. They believe it's possible that such a strike could be the cause behind the Ordovician extinction, approximately 440 million years ago.


Kemo D. 7

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