Do newer stars in globular clusters die before they get old?

According to theories of star life cycles, when a typical star exhausts its hydrogen fuel, it goes through a set of end-life stages before expiring, expanding and contracting over time. However, a new analysis of a globular cluster orbiting the Milky Way found that the younger generation of stars didn’t seem to reach the later stage of life known as the asymptotic giant branch phase. The astronomers conducting the study discovered this by looking for emission from sodium atoms in stellar atmospheres; since the older generation of stars has far less sodium than the younger generation, its presence is a marker of when a given star formed. None of the asymptotic giant stars in the globular cluster had the expected sodium emission, meaning that something weird was happening.

However, a new observation of one of the Milky Way’s globular clusters turned up a problem: the younger generation of stars in the cluster didn’t seem to be passing through the asymptotic giant phase. Simon W. Campbell and colleagues found that while the red giant star population included stars from both older and younger populations, the asymptotic giant stars only represented the older generation. That’s in strong contradiction to theory: the era of a star’s formation shouldn’t affect its life cycle. The reason for this deviation is mysterious. [Read more…]

The headline to the Ars Technica story, alas, is misleading. There’s no reason to think the younger stars are living longer; in fact, it’s likely those stars are burning out sooner than expected for some unknown reason, unless there’s a way they’ve found to destroy or mask the sodium in their atmospheres.

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