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Blue Stragglers

One popular theme of 1950s sci-fi movies was rejuvenation. A woman would stay youthful by stealing various bodily fluids from others. And some stars do the same thing.

Blue stragglers are found mainly in globular clusters — densely packed families of stars. The clusters are old — more than 10 billion years. Blue stars, though, are hot and vigorous, so they burn out quickly. The only stars in these clusters today should be more sedate, so they should be fairly red. Any blue stars in the clusters, then, are oddballs.

Blue stragglers most likely have been rejuvenated — they’ve gained a youthful look by stealing the lifeblood of other stars.

Some of them probably have done so gradually. They have close companion stars. If the companion is more massive, it dies earlier. As it does, it puffs up, allowing the other star to take some of its gas. The recipient gets bigger and hotter. The higher temperature makes it look blue.

Others have gained the youthful look more dramatically — by merging with another star. The combined star is also bigger, hotter, and bluer — a single star rejuvenated by another.

The first blue stragglers were found in the cluster Messier 3 — a family of half a million stars about 34,000 light-years away. It’s in the constellation Canes Venatici, the hunting dogs, and is easily visible through binoculars. It climbs into good view in the east-northeast by midnight, and stands high overhead at dawn.

Script by Damond Benningfield

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