Magazine article Science News

Dino Death: A Stellar Weapon

Magazine article Science News

Dino Death: A Stellar Weapon

Article excerpt

Two astronomers have refined previous estimates of how close certain types of stars must come to the Oort Cloud, a proposed reservoir of comets at the fringes of the solar system in order to trigger a comet shower that might wreak havoc on Earth. The comets most susceptible to the tug of a passing star are those with highly elongated orbits--that is, bodies whose farthest point from the sun is about 30,000 times Earth's distance from the sun and whose closest approach might equal Neptune's distance from the sun. If such comets are jostled out of position, they could venture near Earth as a comet shower about 2 million years later.

Although researchers have evidence of only one large body slamming into Earth around the time that the dinosaurs began dying out, some scientists believe the creatures may have taken several million years to become extinct and that a series of comets may have contributed to the death toll.

Over the past year or so, researchers at NASNs Jet Propulsion Laboratory (JPL) in Pasadena, Calif., have zeroed in on the triple star system Algol and the single star Gliese 710 as nearby bodies that might have disturbed the Oort Cloud in the recent past or may do so in the near future.

Recently, however, Lawrence A. Molnar and Robert L. Mutel of the University of Iowa in Iowa City examined the same stars but took into account some subtle effects--the motion of the sun as it orbits the Milky Way compared to the motion of nearby stars orbiting the galaxy, and the differences in the galaxy's gravitational pull on the sun and on neighboring stars. …

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