A Moment of Science

Overweight Stars

Astronomers have proposed two theories to explain the mysterious origin of blue stragglers.

Cluster of stars in space

Photo: Image Editor (flickr)

Star cluster in the Milky Way galaxy

It’s well known that obesity is a global problem. Even our pets are getting too fat for their own good. But at least we’re not alone in our penchant for being overweight.

Take, for example, stars. Yes, stars, as in the self-contained, continuous nuclear furnaces we see twinkling in the night sky. About fifty years ago astronomers discovered what they called blue stragglers–unusually massive stars in star clusters that are hotter, bluer, and younger than the stars around them.

Astronomers have proposed two theories to explain the mysterious origin of blue stragglers. In one, blue stragglers result from the interaction of stars in a binary pair–that is, two stars orbiting their common center of mass. In the other, the massive stars are the products of collisions between at least two unrelated stars.

Research has finally solved the puzzle: most blue stragglers appear to be the result of so-called stellar cannibalism, where one star in a binary pair siphons plasma from its partner to form a single, uncommonly massive, reborn star.

Blue stragglers are commonly found in globular clusters–groups of around 100,000 or more stars grouped closely together. The next step in studying these unusual stars is to determine whether they form spontaneously or are influenced by stars in the vicinity.

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