Supernovae have inspired a galaxy of post-apocalyptic sci-fi novels, but is Earth really close enough to send us running to our basement shelters?
While our planet was bombarded by the lethal radiation of these astral death throes millions of years ago, there hasn’t recently been a supernova within striking distance. Unless you count 2.6 million years ago as recent. That particular explosion was thought to be further away than it actually is, which is why researcher Adrian Melott, professor of physics and astronomy at the University of Kansas, recently published new findings in The Astrophysical Journal updating evidence and revising the estimated distance to about half of what it was previously believed to be—150 light-years.
Sound scary? It’s still nowhere near setting off a mass extinction.
The “kill zone” for a supernova is around 40-50 light-years from Earth. Meaning, something that wreaked cosmic havoc at triple the distance may extend its reach to our vicinity but is unlikely to bring on doomsday. Magnetic field lines also determine if those deadly rays are deflected, since supernova radiation is unable to cut across them. The disturbing alt version of this occurs if a ray encounters a line in the same position, which it will then use as a superhighway through the atmosphere. An onslaught of subatomic particles would scatter on the surface. In the hypothetical event this happened, Melott and his colleagues believe it would expose us to excessive radiation.
“Imagine every organism on Earth gets the equivalent of several CT scans per year,” he theorized. “CT scans have some danger associated with them. Your doctor wouldn't recommend a CT scan unless you really needed it."
Cosmic rays messing with our atmosphere would spike bio-aberrations like mutations and cancer. You would also have about a month of dealing with a persistent (and probably annoying) blue LED-like light glowing in the night sky, which would mess with your melatonin production and temporarily turn you into a coffee zombie. The most cataclysmic afterthought of a supernova would be atmospheric ionization—what happens when the rays issuing from it forge a path for lightning to ignite by beating the electrons out of atmospheric atoms. Lightning storms could send wildfires raging and even change the ecology of some areas. However, the distance of this supernova is far enough from the kill zone that such phenomena would only happen at this intensity if the radiation found its magnetic field superhighway.
Still, Melott is often approached by the paranoid who want to know if they should marathon Doomsday Preppers.
"I tell them they should worry about global warming and nuclear war, not this stuff," he said. "There's nothing close enough to cause this kind of event in the very near future."