For immediate release October 1, 1998
Contact: Steve Koppes, (773) 702-8366, [email protected]
Astronomers to assess their understanding of supernovae explosions at University of Chicago Oct. 29-31
Two independent research groups created a sensation early this year when, using exploding stars from the most distant reaches of space as their astronomical measuring devices, they separately presented evidence that the universe will expand forever.
But these findings could still backfire on the astronomical community, said Jens Niemeyer, the Enrico Fermi Fellow at the University of Chicago's Enrico Fermi Institute.
The physics of exploding stars is not yet fully understood. Can they really be used to foretell the ultimate fate of the universe? An international group of astronomers will attempt to answer that question during a workshop on Type Ia Supernova Theory taking place Oct. 29 to 31 at the University of Chicago.
"Type Ia supernovae are believed to be thermonuclear explosions of white dwarfs," Niemeyer said. "The explosion is a complete disruption of the white dwarf. There's no compact remnant, no neutron star or anything left over."
Some white dwarfs, which are compact stars whose nuclear fuel has been exhausted, exist in binary systems consisting of two stars. The white dwarf draws mass from its binary companion until it reaches a critical size. The heat intensifies, igniting a thermonuclear explosion that blasts the white dwarf to bits.
Such explosions shine so brightly that astronomers use them as astronomical measuring devices, called standard candles, to help determine the expansion rate of the universe. Theoretically, by comparing the light characteristics of type Ia supernovae at the edge of the known universe to similar ones nearby, scientists can estimate whether the universe will expand forever or eventually collapse back into itself under the force of gravity.
Workshop organizers Niemeyer and James Truran Jr., Professor in Astronomy & Astrophysics, are members of a Chicago research group that specializes in the physics of type Ia supernovae.
"We will focus on how little or how much we understand of the explosions themselves in order to get a better feeling for their use as standard candles," Niemeyer said.
About 80 scientists are expected to attend the workshop, including representatives of the research groups whose findings triggered the meeting. Speakers will include Saul Perlmutter of the Supernova Cosmology Project at the Lawrence Berkeley National Laboratory in California and Alex Filippenko of the international High-Z Supernova Search Team.
Both groups separately announced early this year that the expansion rate of the universe was not what most astronomers had assumed it was.
Most astronomers have assumed that a force called the cosmological constant has a value of zero. The latest supernovae findings suggest that the cosmological constant has a small but significant value, enough to measurably affect the expansion rate of the universe.
Albert Einstein introduced the concept of the cosmological constant but later called it his greatest mistake. According to Einsten's 1917 theory of general relativity, the universe should be expanding. He introduced the cosmological constant into his equations to account for a universe that was in steady state, because at the time, astronomers did not know that the universe was expanding. After Edwin Hubble discovered that the universe does indeed expand in 1929, Einstein recanted his cosmological constant.
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Journalists are welcome to attend the workshop. For more workshop information, see http://bigwhirl.uchicago.edu/workshop/
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