Jan. 10, 2003

Contact: Todd Cohen, University Relations, (785) 864-8858; or Ranjit Arab, University Relations, (785) 864-8855.

KU professor's research finds diminished likelihood of supernova doom

LAWRENCE -- We all can rest a little easier now knowing that the odds of cosmic debris from a supernova destroying life on Earth have diminished, thanks in part to the research of a University of Kansas scientist.

Claude Laird, adjunct professor of physics and astronomy at KU and project coordinator for the Research Initiative for Scientific Enhancement program at Haskell Indian Nations University in Lawrence, helped NASA scientists determine that a massive star explosion -- or supernova -- would have to be much closer than previously thought for it to have a devastating effect on the earth's atmosphere.

Previously, scientists believed that a supernova as far away from Earth as 55 light years could release gamma and cosmic rays that would significantly damage our ozone layer and allow cancer-causing ultraviolet radiation to saturate the planet's surface. Laird and the NASA scientists, however, recently determined that the explosion would have to be about 26 light years of earth.

In addition, the scientists determined that supernovae that close to Earth are much less likely to occur than previously thought, Laird said. In fact, they only happen at a rate of approximately one every 670 million years.

"From beyond that point, the impact falls off quickly," he said. "All of this together gives us greater confidence that we're not in as much danger as some earlier studies had indicated."

Laird and his colleagues presented their findings at the American Astronomical Society meeting in Seattle this week. Their paper will be published in the March 10 edition of the Astrophysical Journal. Neil Gehrels of the NASA Goddard Space Flight Center in Greenbelt, Md., is the study's principal investigator.

The scientists were able to reach their conclusion by using the latest advancements in technology and theoretical modeling, including the NASA Goddard Two-Dimensional Photochemical Transport model of the Earth's atmosphere that is now used to monitor ozone depletion caused by chlorofluorocarbons.

For his part, Laird used gamma ray data from an actual supernova that occurred in 1987 to simulate the effects it would have on Earth's atmosphere. That supernova, called SN1987a, occurred outside of the Milky Way galaxy and was too far away to harm Earth. Still, it gave Laird the information he needed to simulate how a supernova would affect Earth, in effect by moving it closer.

It was the first time scientists used data from an actual supernova in this type of study.

"I used the gamma ray and cosmic ray data from SN1987a as the model inputs to estimate the atmospheric ionization and the resulting ozone layer depletion that would occur -- and I did that work right here in the Space Physics Lab at KU," Laird said.

Laird credits his mentor, Tom Armstrong, professor of physics and astronomy at KU, with helping bring the important NASA research to campus. Armstrong, who will retire at the end of the spring semester, has been involved in several NASA projects, including developing a measuring device for the Cassini spacecraft, which is orbiting Saturn.

"Tom Armstrong has done a lot of cutting-edge research here at KU," he said. "And that has led to further opportunities for other scientists here."

Lately, Hollywood movies and scientists alike have been intrigued with doomsday scenarios involving asteroids colliding with Earth. Although there is some cause for concern in that area, Laird said, a supernova in range to harm our planet would be a potentially worse situation.

"It's something you don't talk about a lot because there is nothing you can do about a supernova," he said. "Theoretically, we might be able to do something about an asteroid or a comet if we have enough advanced warning and that's why an effort has been made recently to catalog such objects. But there's nothing we can do if a supernova goes off -- we're just along for the ride."

Still, he said, he takes pride -- and comfort -- in the fact that his research demonstrates that this potentially destructive scenario is even less likely to happen.

"It's one less thing to worry about," he said. "It's kind of nice to have some good news for a change."