Which type of stellar instability provides a direct reading of internal physics useful for measuring cosmic distances?

Answer

Regular pulsations in certain variable stars (standard candles).

Certain pulsating stars, such as Cepheid variables, have a pulsation period directly linked to their true intrinsic brightness. Observing this instability allows astronomers to use them as standard candles to measure cosmic distances precisely.

Which type of stellar instability provides a direct reading of internal physics useful for measuring cosmic distances?
instabilitystar