359 million years ago, Earth’s one of its worst extinctions occurred, and a team of researchers at the University of Illinois think it could be caused by a series of explosions of supernovae no more than 35 light-years away.
Every now and then something terrible happens to life on earth. The biggest episodes we call extinction events. The last big one happened about 65 million years ago, and was a very rough time for dinosaurs, but did pretty great for the mammals. But that extinction event was just the latest in a long series of disruptions in the many lives on the planet. One of the earliest extinction events occurred about 359 million years ago on the border of the Devonian and Carboniferous periods.
We are not exactly sure what happened to extinction. There is no clear smoke pistol like there is for proving the asteroid impact of the one who killed most dinosaurs. But a team of researchers from the University of Illinois proposes a radical and other worldly explanation: supernovae.
The main evidence that leads to this hypothesis is the fact that fossils of plants left over from that tumultuous era show signs of nasty sunburns: excessive UV exposure. The earth’s ozone layer does a fantastic job of blocking almost all of the sun’s UV radiation, so the fact that these regions received an extra dose means that our ozone layer had to be depleted. There are many potential geological processes that can scrub our ozone layer, and there is also one celestial.
The intense radiation of a close enough supernova explosion can disperse our ozone, exposing the earth’s surface to the sun’s UV attack. In general, intense UV radiation is not too great for living things, hence an extinction event.
The researchers estimated that a single supernova explosion within 65 light-years could be enough to suppress our ozone layer for about 100,000 years. The fossil record indicates that life was three times longer, however, so researchers speculate that the supernova was not alone. This is not a crazy idea, because stars tend to cluster and large stars tend to go relatively close as supernovae.
But so far this is an untested hypothesis. The next step is to find evidence in those fossil layers of an excess of certain radioactive elements such as plutonium-244. This element is not produced naturally on Earth, and so the only way to exist in that layer of sediment is to put it there as the supernova’s shock wave sweeps across our planet.
If you’re worried about the next supernova explosion, do not stress. The closest supernova candidate to Earth is the star Betelgeuse, which lies a safe 600 light-years away.
