Mystery of age-defying blue stars solved

The Hubble Telescope captures blue straggler stars in the Milky Way bulge. Credit: NASA, ESA, W. Clarkson (Indiana University and UCLA), and K. Sahu (STScl) 

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EVANSTON, Ill., Oct. 19 (UPI) -- U.S. astronomers say they've solved the mystery of distant stars that don't show their age, burning hotter and bluer than they should at their age.

Until now, scientists have lacked the observations with which to test theories about the so-called blue stragglers, but two astronomers from Northwestern University and the University of Wisconsin-Madison say they think they have the answer.

Blue stragglers are binary stars that are kept burning blue and bright by eating up the mass of a companion star, said astrophysicist Aaron M. Geller of Northwestern and Robert Mathieu, chair of the astronomy department at UW-Madison.

This extra fuel allows the straggler to continue to burn and live longer than it otherwise would, while the companion star is stripped bare leaving only its white dwarf core.

"We think we have a good understanding of stellar evolution, but it doesn't predict blue stragglers," Geller said. "People have been trying to explain the origin of blue stragglers since their discovery in 1953, and now we have the detailed observations needed to identify how they were created."