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Nemesis: searching for the sun's deadly companion star.

If the sun is not a member of a binary or multiple star system, it is among the minority of stars. Yet if the sun has a companion, no one in thousands of years of observing has found it. It must be both distant and dim. A search for such a solar companion is now under way in Berkeley, Calif. Richard Muller, Jordin Kare and Carl Pennypacker of the Lawrence Berkeley Laboratory are using a telescope at the University of California's Leuschner Observatory in the Berkeley hills, and are just completing their first series of observations.

They call the putative companion star Nemesis, after the Greek goddess of doom. The impulse to search for such a star now and the rationale for the name come from paleontology. Evidence recently put together seems to show mass extinctions of biological species at intervals of 26 million years. Why would this happen? One theory suggests that changes in living conditions are triggered by comets striking the earth after their motion was changed by an impulse due to the passage of Nemesis (SN: 4/21/84, p. 250).

From Kepler's law, calculation shows that for an orbit of 26 million years, the semimajor axis of Nemesis's orbit has to be 88,000 times that of the earth. Doubled, this gives 2.8 light-years for the major axis or longest dimension of the star's orbit. That puts it closer than any known star to the sun, so Nemesis should show a larger parallax than any now known.

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Title Annotation:From the Archive
Author:Quill, Elizabeth
Publication:Science News
Article Type:Brief article
Geographic Code:1USA
Date:Dec 3, 2011
Words:254
Previous Article:Bat comeback.
Next Article:Seeking a friendlier companion.
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