Classical pulsators¶
Many different kinds of star undergo pulsations (vibrations) of some sort. Like strings, drumheads, the Earth and most objects with clear boundaries, all stars have resonant modes of pulsation. Whether they are observed to pulsate mostly depends on whether some process excites the pulsations to measurable amplitudes.
The many classes of pulsating star are an intersection of the driving mechanisms, how stars evolve and the populations of stars that make up the Milky Way (and other galaxies). The simplest distinction is between the solar-like oscillators, where pulsations are driven incoherently by near-surface convection, and other (mostly coherent) pulsators, where pulsations are usually driven by an instability caused by how opacity depends on temperature.
I’ve branded the latter classes, presented in this section, the classical pulsators because their amplitudes are larger and many have been known for much longer than we have observed solar oscillations, let alone solar-like oscillations.