September 22, 2008

Looking Back At A Colossal Collision

Enormous masses of dust floating around a binary star system suggest that two Earth-like planets demolished each other in a violent collision.

"It's as if Earth and Venus collided with each other," said Benjamin Zuckerman, an astronomer at the University of California Los Angeles, who worked on the study.

"Astronomers have never seen anything like this before; apparently major, catastrophic, collisions can take place in a fully mature planetary system."

The team from UCLA, Tennessee State University and the California Institute of Technology said it spotted the dust orbiting a star known as BD +20 307, 300 light-years from Earth in the constellation Aries. The findings were published in the Astrophysical Journal.

The observations are looking back 300 years in the past because a light-year is the distance light travels in a year, or about 6 trillion miles.

"If any life was present on either planet, the massive collision would have wiped out everything in a matter of minutes: the ultimate extinction event," said Gregory Henry of Tennessee State University.

Scientists say BD +20 307 appears to be composed of two stars that are very similar in mass, temperature and size compared to the Earth's sun.

Experts believe they spin about their common center of mass every 3 1/2 days.

"The planetary collision in BD +20 307 was not observed directly but, rather, was inferred from the extraordinary quantity of dust particles that orbit the binary pair at about the same distance as Earth and Venus are from our sun," Henry said.

"If this dust does indeed point to the presence of terrestrial planets, then this represents the first known example of planets of any mass in orbit around a close binary star."

When the team first spotted the system in 2005, researchers believed it only consisted of one star.

They reported it was surrounded by more warm orbiting dust than any other sun-like star known to astronomers.

"This poses two very interesting questions," said Tennessee State's Francis Fekel. "How do planetary orbits become destabilized in such an old, mature system? Could such a collision happen in our own solar system?"


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