"Blue Straggler" Stars Cannibalize to Stay Young

January 23, 2009

It's a star-eat-star universe out there.

Old stars known as blue stragglers keep the appearance of youth by stealing mass from other stars, according to new research.

Christian Knigge of Southampton University in the U.K. and colleagues think most blue stragglers are members of binary star pairs that gradually pull matter from their partners.

This cosmic cannibalism allows smaller, aging stars to swell to sunlike proportions, extending their lives by hundreds of millions of years.

According to the study authors, the new finding refutes a leading theory that such rebirths were the results of stellar collisions.

"Personally, I always actually liked the idea … that stars like our sun might literally smash into each other and form a new, more massive star," Knigge said of the opposing theory.

"Compared to that, even stellar cannibalism seems almost pedestrian."

Fountain of Youth

Astronomers have been puzzling over blue stragglers for more than five decades, because the stars are suspiciously young-looking and overweight for their ages.

Most blue stragglers are stars with the same to twice as much mass as our sun. They are found in globular clusters—gravitationally bound groups of roughly a hundred thousand stars that are thought to be about 12 billion years old. (See a Hubble picture of globular cluster M13.)

A typical star similar in mass to the sun should live for only a few billion years. That means if a given blue straggler formed with the rest of its star cluster, it should have died billions of years ago, Knigge said.

To try and solve the mystery, Knigge and colleague examined blue stragglers in 56 globular clusters.

Continued on Next Page >>


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