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Nemesis: Does the Sun Have a 'Companion'?
By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
03 April 2001
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Far-out idea
The orbit assumed for Nemesis is an unusual one, Muller admits. No star has ever been found to orbit so far from a companion. "And that really bothers people," he said. "It makes them think that this is a really far-out idea, literally."
But computer models developed by Muller and his colleagues predict that such an orbit must occur at some point in the evolution of most binary star systems. "We just haven't found such systems yet," he said.
And while Muller appreciates the natural and healthy skepticism of other scientists, he figures they are not interested in funding a search because they erroneously assume that Nemesis cannot be found.
Jonathan Tate is the director of Spaceguard U.K., which lobbies for a government response to the threat of asteroids. Tate is among those who see no rush to find Nemesis. He would rather see money spent on more immediate searches for asteroids closer to Earth that might prove to be humanity's undoing in coming decades or centuries.
As Tate points out, proving that mass extinctions occur every 26 million years, regardless of the cause, is only of academic interest: Humans may not likely to be around to care, as many researchers don't expect our species to last that long. If we do survive, there will likely be plenty of time to worry.
Questioning periodicity
Meanwhile, many scientists see little or no credibility to the studies alleging periodicity in mass extinctions, and hence no need for a Nemesis theory.
Numerous studies have reported cycles in either impacts or mass extinctions. The period between peaks in these studies mostly range from 26 million to 35 million years. Andrew Glikson of the Australian National University says that trying to pin down things that happened so long ago is no simple challenge. For one thing, space rocks that land in the ocean leave few clues, Glikson points out, and Earth is roughly two-thirds water.
And Earth has always had a crust that is on the move. Evidence gets buried, destroyed, and folded into oblivion by the same process that creates mountains and moves continents.
"Some of the suggested periodicities are more likely to represent statistical artifacts than robust observations," Glikson said.
David Raup, a University of Chicago paleontologist, made the original mass-extinction periodicity argument two decades ago along with colleague J. John Sepkoski. The pair studied marine fossil records over a 250 million-year period that they say showed significant spikes every 26 million years.
"To me, the periodicity idea is as well supported as many ideas that have been adopted into the conventional wisdom, but the scientific community is heartily skeptical," Raup told SPACE.com. "Of the 15 or so re-analyses of our data published since the original paper, about half support periodicity and half reject it. It's is still very much in the eye of the beholder."
Muller supports the statistics more emphatically.
"There is a peculiar pattern in mass extinctions, something that cannot be dismissed as a statistical fluctuation," Muller said. "It requires some explanation."
Raup, now retired from active research, would not venture a guess as to when or whether Nemesis might be found, but he expressed hope in the idea: "I am glad Rich [Muller] is still working on it because it may take a lot of effort, and he's the best."
Next page: Links to Planet X and black holes
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