Earth Safe From Gamma Ray Bursts

ByABC News
May 10, 2006, 3:17 PM

May 10, 2006 — -- You can breathe easier.

Scientists say that Earth is at far lower risk from potentially devastating gamma ray bursts than was previously thought.

What's a gamma ray burst? A GRB, as they are called in the astronomy community, is a flash of extremely high-energy radiation that occurs as a massive star collapses and explodes.

If a gamma ray burst occurred in our own Milky Way galaxy, scientists said it could do terrible things to Earth, even cause mass extinction.

"It destroys the ozone and might cause acid rain. It could cause mutations," said Andrew Fruchter, an astronomer with the Space Telescope Science Institute. "If it happens close enough, then it gets brighter than the sun. And then it starts lighting fires on Earth. So you know, you don't want one of these."

But Fruchter and his colleagues from the University of Hertfordshire in the United Kingdom say it's not time to abandon the planet just yet.

"It's much less likely that a GRB would go off in our galaxy than we had thought," Fruchter said. "And that's because they don't like galaxies like ours."

In results published today in the online edition of the journal Nature, Fruchter and his team studied images of gamma ray bursts gathered by the Hubble Space Telescope. They found that GRBs generally occur in very distant galaxies with chemical makeups far different from our own.

Heavy elements found in the Milky Way -- like carbon, nitrogen and oxygen -- "get in the way" and prevent the growth of the massive stars where gamma ray bursts happen.

Fortunately, says Fruchter, the closest of those stars is about 150,000 light-years away. And while he can't totally rule out a gamma ray burst occurring locally, he said it is "very, very unlikely."

"Personally," he said, "in the list of top worries, this doesn't make it."