Astronomers describe death of planet

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UNIVERSITY PARK, Pa., Aug. 20 (UPI) -- An international team of astronomers says they've seen the first evidence of a planet's destruction as its aging star became a red giant at the end of its life.

"A similar fate may await the inner planets in our solar system, when the sun becomes a red giant and expands all the way out to Earth's orbit some 5 billion years from now," team member Alex Wolszczan, a professor of astronomy and astrophysics at Penn State University, said.

Wolszczan and his international colleagues detected evidence of the missing planet's destruction while studying the aging star and searching for planets around it.

The evidence includes the star's peculiar chemical composition, and the highly unusual elliptical orbit of its one surviving planet, a Penn State release said Monday.

"Our detailed spectroscopic analysis reveals that this red-giant star, BD+48 740, contains an abnormally high amount of lithium, a rare element created primarily during the Big Bang 14 billion years ago," team member Monika Adamow said.

Lithium is easily destroyed in stars, which is why its abnormally high abundance in this older star is so unusual, the astronomers said.

"In the case of BD+48 740, it is probable that the lithium production was triggered by a mass the size of a planet that spiraled into the star and heated it up while the star was digesting it," Adamow said.

The highly elliptical orbit of the star's remaining planet is more evidence for a destroyed planet, astronomers said.

"Such orbits are uncommon in planetary systems around evolved stars and, in fact, the BD+48 740 planet's orbit is the most elliptical one detected so far."

Gravitational interactions between planets are normally responsible for such peculiar orbits, and the researchers say they believe the missing planet could have given the surviving massive planet a gravitational shove as it spiraled to its destruction, throwing the survivor planet into an eccentric orbit like a boomerang.