New Kansas University research attempts to document how, every 27 million years, the planet goes through a massive wave of extinctions, and casts doubt on an old explanation for the phenomena.

Adrian Melott, a KU professor of physics and astronomy, examined the fossil record back 500 million years and found the pattern of massive drops in the number of species on the planet.

Melott and the co-author of the study, Richard Bambach from the Smithsonian’s National Museum of Natural History in Washington, D.C., didn’t determine a cause for the extinctions, but did address an old hypothesis that attempted to explain them.

Melott said that back in the 1980s other researchers had posited that a small, dark star — dubbed “Nemesis” — orbiting around the sun would occasionally interact with the Oort Cloud, a faraway collection of ice and rock that forms comets. That would send a regular shower of comets down on the solar system, wiping out massive amounts of life on Earth in the process.

If the hypothesis were true, Melott said, the forces of larger objects and other stars would affect Nemesis’ regular orbit enough to jar it off its regular path. Melott said that if Nemesis were the true cause of these extinctions, the extinctions should have been more sporadic.

“They don’t change much over 500 years,” he said.

Still, chances are pretty good — about 99 percent, Melott said — that the extinctions aren’t caused by random occurrences alone.

Fortunately for us, we’ve only had about 11 million years since the last regularly scheduled mass extinction.

“Don’t worry, at least with this one,” Melott said. “But there are extinction events outside of this one, too.”

The Nemesis hypothesis still has its defenders.

Richard A. Muller of the University of California at Berkeley, an author of a paper proposing the dark star and a book called “Nemesis: The Death Star,” told Wired.com Melott is “coming to too strong a conclusion.”

“I would agree with most of what he says, but I think he is overestimating the accuracy of the geologic timescale,” he said. The geological record gives only an approximate sense of when major extinctions happened. “You get them in the right order, but it’s really difficult to get an actual date,” he told the website. “I think the Nemesis hypothesis is still alive.”

The study will be published in an upcoming edition of Monthly Notices of the Royal Astronomical Society.