Suicidal Supernova
Supernovas are among the most powerful explosions in the universe and can rival the strength of a few octillion nuclear warheads, according to NASA.
These super-booms come in two varieties: core-collapse supernovas, which happen when a giant star’s core collapses after 5 million to 20 million years of life; and type-1a supernovas which occur when a white dwarf star detonates after its core gets too dense.
In our galaxy, core-collapse supernovas occur two to four times more frequently than type-1a supernovas, says astronomer Todd Thompson of Ohio State University. And in the Milky Way, a core collapse tends to happen every 100 years or so, he says. Luckily, most will happen at a safe distance of 5 to 10 parsecs, or 16.5 to 33 light-years — too far away to do any real damage.
If supernovas occurred randomly throughout the Milky Way, Earth could expect one every 5 billion years. But because they congregate near the Milky Way’s spiral arms, “we would in fact expect to come within 10 parsecs of a supernova nearly every time we pass through a spiral arm, which is about every 100 million years,” Thompson said.
These stellar fireworks produce x-rays, cosmic rays — electrons, protons and nuclei zooming through space at nearly the speed of light, and gamma rays -- light waves so powerful they’re capable of killing cells.
A supernova’s radiation would destroy the ozone in the atmosphere, increasing the amount of ultraviolet light that gets through. The UV flash could increase skin cancer rates; set off mass die-offs of bacteria and plankton; and precipitate another ice age, Thompson said.
Image courtesy of NASA / JPL