February 27, 2002

Supernovae Specialist Gives Bethe Lectures

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Prof. Stanford Woosley, chair of the department of astronomy at the University of California at Santa Cruz and expert on giant exploding stars called supernovae, has come to Cornell to deliver a three-part lecture series.

The first of the series, delivered yesterday in Rockefeller Hall’s Schwartz Auditorium drew an audience of more than 150 people. The lecture detailed the type of star death called a “Core Collapse Supernovae.”

These lectures, known as the Bethe Lectures, have been given annually for 25 years in honor of Hans Bethe, Cornell’s John Wendell Anderson Professor of Physics Emeritus.

Bethe won the 1967 Nobel Prize in Physics for his advances in understanding the processes that power the sun.

“I like explosions, as long as they are far away and don’t hurt anyone,” said Woosley of his interest in stellar outbursts.

He spoke about the 15th anniversary of the brightest supernovae to be observed from earth in 400 years.

“There is about one supernovae explosion every second in the visible universe, and, for a time, these objects may have the combined luminosity of the rest of the universe,” Woosley said.

Woosley proceeded to explain that most of the heavy elements, such as iron, are made in these explosions.

“The energy involved is equivalent to converting 20 percent of the sun’s mass into pure energy,” Woosley said.

A modest atomic bomb may convert only one gram of mass into energy, Woosley stated.

Woosley spoke primarily on the development of the supernovae model and the obstacles that have marked its progress.

“As it turns out, nature is cruel, three dimensional, linear, and has politicians in it,” said Woosley.

Showing several representations and animations of star convection and dynamics, Woosley offered various explanations of supernova formation and behavior.

“Supernovae collapse in on themselves and the bounce back like a spring leading to an explosion. It’s a very beautiful picture and it’s also

entirely wrong,” said Woosley of the popularized version of supernova formation that has found its way into many textbooks.

Woosley described the process as a period of shrinkage followed by a pause. The pause allows for “bubbles” of energy to form beneath the star’s surface and this then leads to the most violent explosions in the universe, he stated.

A call for cooperation within the scientific community to solve model problems was also made.

“People need to compare results and talk to each other,” said Woosley.

A second lecture, “Type Ia Supernovae” will be held on March 4th at 4:30 p.m.

A final public lecture entitled “Gamma-Ray Bursts: The Brightest Explosions Since the Big Bang” will be held on March 6th at 7:30 pm.

Subsequent lectures will be held in Schwartz Auditorium.

Woosley will remain at Cornell through March 8th.

Archived article by Philip Lane