Milky Way Safe from Gamma-Ray Bursts

In a paper submitted to The Astrophysical Journal, a team of physicists related their conclusion that the Milky Way galaxy has enough metal to prevent long gamma-ray bursts (GRB). A GRB is an energy release that takes place when massive star explodes in a supernova, allowing for the creation of black holes. The energy contained in a GRB is more than our sun will release in its entire 10-billion-year existence, packed into a time duration of a few seconds to tens of minutes.

GRBs are one of many astronomical phenomena that could result in the end of all life on Earth, or serious damage and extinctions among existing life. They are regularly visible in distant galaxies and astronomers have long believed that they must have happened in our galaxy in the past, perhaps accounting for the mass extinctions indicated by the fossil record.

Krysztof Stanek, an Ohio State University in Columbus researcher, says that his team believes that the Earth hasn't been pelted by GRB radiation in the past nor will it be in the future. Analyzing four GRBs in nearby galaxies, they found that all four galaxies contained almost no "metals." (In astronomical terms, "metal" refers to atoms heavier than hydrogen and helium.) This supports theories that metal-rich stars lose so much mass and rotational energy that they can't create GRBs when they die. Apparently, long-duration GRBs occur only in "pristine" galaxies.

The Milky Way has a lot of metal in it since well before the sun and Earth formed, so "We can probably cross GRBs off the rather long list of things that could cause humankind to 'join the dinosaurs' on the extinct species list," the team writes in their paper.

Every few million years, however, the Milky Way does absorb a dwarf galaxy that is probably metal-poor, so it is possible that one of those may have occurred and caused a long-duration GRB nearby in the past. Still, the findings indicate that the GRB is a less-likely cause for past extinctions than some have believed.