ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Sunday, December 8, 1996 TAG: 9612090111
SECTION: NATIONAL/INTERNATIONAL PAGE: A-12 EDITION: METRO
DATELINE: NEW YORK
SOURCE: Associated Press
The universe's most ancient stars could be lying about their ages.
A new theory proposes that globular clusters - dense balls of stars thought to be the oldest in the universe - might be up to 3 billion years younger than they're now thought to be.
If it is proved correct, the theory could help scientists solve one of astronomy's oddest conundrums: the universe appears younger than its oldest stars.
One way out of that mess would be to demonstrate that the stars aren't really so old after all.
NASA astrophysicist Allen Sweigart may have done that with a theory that stars in the clusters make themselves look older by dredging helium gas up from their superhot interiors.
``It may have an important effect,'' said Robert Kraft, an astronomer at the University of California, Santa Cruz. ``This is one more factor that's got to go into the discussion of the ages of globular clusters.''
Pulling the stars down by 3 billion years won't completely solve the apparent generation gap. Current estimates put the most ancient stars at about 14 billion years old and the universe's age at 9 billion years.
But that's not the whole picture, said University of Chicago astronomer David Schramm. Scientists are still so uncertain about both age estimates that the 5-billion-year discrepancy between them could eventually be explained by any number of things. Sweigart's proposal is only one of them.
Even Sweigart said he doesn't want to push the age issue too hard. It's just one possible implication of the helium-mixing process he describes.
``I don't want to claim that my models have proven or shown that the globular clusters are younger,'' Sweigart said. ``It is still a hypothesis that needs to be much more carefully examined and tested against the observations.''
Sweigart's theory, to be summarized in the Jan. 1 issue of Astrophysical Journal Letters, shows how some stars in the globular clusters could be mixing themselves up, moving large amounts of superhot helium from their cores to their outer shells. Through a complex series of steps, that could make the oldest stars look older than they really are.
Most experts consider Sweigart's theory an excellent explanation of some unusual aspects of how stars work. But they're less enthusiastic about his suggestion that it could also make the globular clusters appear younger.
``It will have a huge impact in certain circles. I think in the age of the universe, it won't,'' said Michael Bolte, an astronomy professor at UC-Santa Cruz.
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