Most people know the theory that an asteroid smashed into Earth — hitting what is now the Yucatán Peninsula — and killed off many of the dinosaurs about 66 million years ago.
But that was not the only mass extinction for the planet — just the most well-known. Scientists believe at least five mass extinctions have occurred in the past 500 million years, and not all of them were caused by menacing space rocks. Perhaps two of them, one 372 million years ago and another 445 million years ago, were ice ages.
A new study, based on a census of stars in the Milky Way, suggests those periods of severely cold climates may have begun with stars dying light-years away.
“If a massive star were to explode as a supernova close to the Earth, the results would be devastating for life on Earth,” said Nick Wright, an astrophysicist at Keele University in the United Kingdom, in a statement. “This research suggests that this may have already happened.”
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