Scientists have found that stars – all strikingly similar to the sun – emit deadly superflares every century or so, spewing radiation and highly charged particles that devastate nearby planets.

Superflares haven't occurred in our solar system for at least 2,000 years, and researchers now think they know why.

"I have [studied] nine stars which are proven to be just like our own sun," said Yale University astrophysics professor Bradley Schaefer, who led the study. "You could stick [one] right where our sun is and no would blink. And these all have superflares."

A superflare is an enormous explosion of energy that occurs on the surface of a star. Such blasts spew high-energy particles, ionized gas, and radiation into space.

If the sun produced a superflare, Schaefer said, the heat would be sufficient enough to "turn a winter day into a summer day," and the charged particles striking the upper atmosphere would deplete the ozone so fast that life on earth would die out within a few months.

The sun sends out less powerful solar flares toward Earth at a rate of a few times a decade, Schaefer said. But the damage is minor, resulting in temporary satellite or power grid failures.

"If you have a low-end solar flare, no problem," Schaefer said. "But you take a superflare that's 10 million times as big, and holy moly."

Scientists predict that a medium or high strength flare would deplete the Earth's atmosphere of its ozone for years and result in biological and ecological catastrophe.

"For a year or two everyone gets skin cancer. You wouldn't want to go out for (more than) half a minute at a time. Up and down the food chain, things would just kind of go away," Schaefer said.

"A top-end superflare might even get to the point where it kills cockroaches," he said, referring to the insect's ability to withstand radiation.

Only it isn't likely to happen. Schaefer's team concluded that the sun has not had a superflare in the last 2,000 years because there have been no unexplained mass human extinctions. "If a low-end superflare happened on our sun, it would cause worldwide auroras and heatwaves – it would have appeared in a historical record."