We often think of stars as twinkling, harmless little points of light that fill our night sky with majesty. But stars can be dangerous too. When they come to the end of their lifespan, some stars explode fantastically as supernovae. So what would happen if one of those giant explosions happened nearby?
This week's scenario was suggested by Katie Mack, an astrophysicist who's worked everywhere from Caltech, Princeton, Cambridge, and is now at Melbourne University and studied everything from dark matter to black holes to cosmic strings to the formation of the first galaxies in the Universe. We also called up Phil Plait, who happens to be an expert on the ways that space can kill us, being the author of the book Death from the Skies! The Science Behind the End of the World. Plait is the author of the Bad Astronomy blog for Slate, and is also the writer and host of Crash Course Astronomy.
Together, Mack and Plait walked me through all the ways that a nearby supernovae could wreak havoc with our planet. By nearby, I mean anywhere from 50 to 150 lightyears away. There are stars that far away from us right now, though thankfully none of them are at risk of blowing up any time soon. But that doesn't mean a supernova couldn't go off nearby. Stars are always in motion, and a star that might be nearing the end of its life could swing into our neighbourhood and go off.
Either way, the first people to know that we were in trouble would probably be researchers sitting in a mine under a mountain in Japan, working at the Super-Kamioka Neutrino Detection Experiment. Here's a delightful construction video for the experiment, that explains how it works:
So how do neutrinos get here first, if nothing travels faster than light? When a supernova goes off neutrinos get a head start. Because neutrinos don't really interact with anything, they get shot out from the explosion at top speed immediately. The light, on the other hand, bounces all around this giant fireball before it gets shot out. So here, on Earth, we'd detect those neutrinos first. Whether or not that signal would be far enough ahead of the light from the supernova to be helpful is unclear — the neutrino signal might only give us minutes or hours of warning.
After the neutrinos, we'd be bathed in a whole lot of light that our planet and our technologies won't deal with very well. Most satellites will be fried, and the astronaut on the space station might not make it out alive. Here on Earth, the light would probably burn off the ozone layer, which in turn could kill tons of plants and animals, and knock out some of our biggest oxygen producing organisms like plankton.
Check out the episode for a fuller explanation of all those effects and more.