Deadly Gamma Ray Burst May Have Caused Mass Extinction

In theory, a supernova thousands of light-years away could release gamma-rays that would fry most life on Earth. But the star must be positioned exactly right for this to ever happen, and there's no way to prove it. Until now.

The Ordovician Extinction of 450 million years ago isn't nearly as famous as the K-T event that wiped out the dinosaurs 65 million years ago or the Permian-Triassic of 250 million years ago, which is often called the Great Dying and killed off 96% of all marine life and 70% of land animals. But the Ordovician was still plenty bad, driving more than 60% of all marine species extinct - and since nearly all complex life still lived in the sea back then, that was particularly devastating.

We still don't know what exactly happened with the Ordovician - we know that there were two separate major extinction events separated by about a million years. Carbon dioxide was heavily involved in one of these extinctions, which suggests a likely culprit for at least one of them was extreme volcanic eruptions.

It's the other extinction event that defies easy explanation, and the quest to explain this mystery has led a small group of scientists to put forward a radical hypothesis: it was all caused by a gamma-ray burst. Specifically, this burst must have come from a massive stellar explosion known as a hypernova - an explosion at least a hundred times more powerful than the average supernova - that happened about a thousand light-years away. Certainly, if a gamma-ray burst from an extremely powerful hypernova ever did hit Earth, it would be utterly devastating. A powerful burst lasting just ten seconds would be enough to strip the planet of half of the ozone layer, bathing all organisms near the surface in lots of ultraviolet radiation.

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