Shakin' Red Giants in NGC 6397

A way long time ago, I introduced the concept of asteroseismology. It's a pretty interesting concept that uses the vibrational modes of stars like we do seismology on Earth to probe the interior of stars. When I first wrote on it, a friend from MSU was still working on it, so I heard a lot about it, and intended to write more on it (I even created a tag for it). But I never really did.

One of the things about this technique is that it requires you to have a good handle on how the star you're observing is vibrating. Any any potential star for this has to be vibrating in the right way. Variations like the ones from Cepheids can't give us the information we need. Delta Scuti stars are a class of variables that fits the bill, but finding more classes always helps to increase our knowledge. (In theory most stars will have the right kind of vibrations, but will generally just be too small to notice from any distance.)

A new paper suggests that we may have discovered a new class: Metal poor red giants.

In observing several of these stars, they found at least one that seems to be jiggling just right for the oscillations necessary (called "solar-like" for historical reasons). Several others seemed to be exhibiting the same sort of pulsations, but due to shoddy data with low signal-to-noise ratios as well as some overexposing, they couldn't be sure.

As such, the authors are calling this discovery "tenuous". Still, it's an interesting starting point for further investigation.

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Stello, D., & Gilliland, R. (2009). SOLAR-LIKE OSCILLATIONS IN A METAL-POOR GLOBULAR CLUSTER WITH THE

The Astrophysical Journal, 700 (2), 949-955 DOI: 10.1088/0004-637X/700/2/949