Astronomy

Blue Straggler Stars Suck the Life Force of the Young

According to legend, vampires stay youthful for all of eternity by feeding on the blood of humans—the younger, the better. In space, something similar happens. Blue stragglers stay young much longer than they should. If you're familiar with vampires, the reason won't surprise you.

Masters of Disguise

A globular cluster is an ancient mass of densely packed stars. We know they're ancient because they generally can't form today—they were born out of the huge clouds of gas that were plentiful near the beginning of the universe. The thing about old stars is that they almost always have low mass, since the more massive a star is, the faster it burns up its hydrogen fuel. A star's color comes from the combination of its temperature and its mass, so cool, low-mass stars burn redder than high-mass stars, which burn bluer. To put it simplistically, a young, hot, massive star burns blue; an old, cool, low-mass star burns red. With us so far?

With that logic, because globular clusters are groups of ancient stars that formed at the same time, there shouldn't be any massive blue stars among them. But sometimes there are. The only way that's possible is if the blue stars — dubbed "blue stragglers" for their refusal to get old with the rest of the cluster — formed after the others. Or if something evil is afoot.

They Want to Suck Your Hydrogen

There are technical properties about these stars that let astronomers know they didn't form after the others—they're young stars in disguise. According to a summary of a study published in The Astrophysical Journal, "The only way to explain the blue stragglers being brighter and bluer...is if they went through some rejuvenating process." That rejuvenating process? Sometimes it's the collision of two stars, but most often, it's one star sucking mass and hydrogen fuel from another star. A clue that points to this conclusion lies in the fact that blue stragglers most often show up in densely packed clusters, where stars have a chance to interact. We've even seen them in our own Milky Way galaxy. That's right: we've got vampires in our neighborhood.

To explore the stars in your own neighborhood, check out "NightWatch: A Practical Guide to Viewing the Universe," written by Terence Dickinson and illustrated by Adolf Schaller. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

M3 Globular Cluster and Blue Stragglers

Written by Ashley Hamer January 19, 2017

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