Washington, September 24 : Astronomers have spotted the mighty collision of two terrestrial planets orbiting a mature sun-like star, an event which is being compared to a hypothetical clash of the Earth and Venus, which may have been the ultimate extinction event.
The collision was detected by astronomers at UCLA, Tennessee State University and the California Institute of Technology, US.
"It's as if Earth and Venus collided with each other," said Benjamin Zuckerman, UCLA professor of physics and astronomy and a co-author on the paper.
"Astronomers have never seen anything like this before. Apparently, major catastrophic collisions can take place in a fully mature planetary system," he added.
"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 co-author Gregory Henry, an astronomer at Tennessee State University (TSU).
"A massive disk of infrared-emitting dust circling the star provides silent testimony to this sad fate," he added.
Zuckerman, Henry and Michael Muno, an astronomer at Caltech at the time of the research, were studying a star in the constellation Aries, known as BD+20 307, which is surrounded by 1 million times more dust than is orbiting our sun.
"We expected to find that BD+20 307 was relatively young, a few hundred million years old at most, with the massive dust ring signaling the final stages in the formation of the star's planetary system," Muno said.
Those expectations were shown to be premature, however, when Carnegie Institution of Washington astronomer Alycia Weinberger announced on May 20, 2008, that BD+20 307 is actually a close binary star - two stars orbiting around their common center of mass.
"That discovery radically revised the interpretation of the data and transformed the star into a unique and intriguing system," said TSU astronomer Francis Fekel.
The new spectroscopic data confirmed that BD+20 307 is composed of two stars, both very similar in mass, temperature and size to our own sun. They orbit about their common center of mass every 3.42 days.
"The patterns of element abundances in the stars show that they are much older than a few hundred million years, as originally thought," Fekel said. "Instead, the binary system appears to have an age of several billion years, comparable to our solar system," he added.
"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.
According to astronomers, the dust-forming collision near BD+20 307 must have taken place rather recently, probably within the past few hundred thousand years and perhaps much more recently.