Stardust evidence points to planet collision
Masses of dust floating around a distant binary star system suggest
that two Earth-like planets obliterated each other in a violent
collision, U.S. researchers reported.
"It's as if Earth and Venus collided with each other," Benjamin
Zuckerman, an astronomer at the University of California Los Angeles,
who worked on the study, said in a statement.
"Astronomers have never seen anything like this before; apparently
major, catastrophic, collisions can take place in a fully mature
planetary system."
Writing in the Astrophysical Journal, the team at UCLA, Tennessee
State University and the California Institute of Technology said it
spotted the dust orbiting a star known as BD +20 307, 300 million
light-years from Earth in the constellation Aries. A light-year is the
distance light travels in a year, or about 6 trillion miles (9.5
trillion km). So the observations are, in essence, looking back in time
300 million years.
"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. BD
+20 307 appears to be composed of two stars, both very similar in mass,
temperature and size to the Earth's sun. They spin about their common
center of mass every 3 1/2 days or so.
"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."
In July 2005, the team reported it had spotted the system, then
believed to consist of a single star. 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?"
WASHINGTON, (Reuters)
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