Solar-like oscillations

The oscillations are standing pressure and mixed pressure-gravity modes that are excited over a range in frequency, with the amplitudes roughly following a bell-shaped distribution.

Because of the small amplitudes of the oscillations, their study has advanced tremendously thanks to space-based missions[1] (mainly COROT and Kepler).

[2][3] In red giants, mixed modes are observed, which are in part directly sensitive to the core properties of the star.

These have been used to distinguish red giants burning helium in their cores from those that are still only burning hydrogen in a shell,[4] to show that the cores of red giants are rotating more slowly than models predict[5] and to constrain the internal magnetic fields of the cores[6] The peak of the oscillation power roughly corresponds to lower frequencies and radial orders for larger stars.

For the Sun, the highest amplitude modes occur around a frequency of 3 mHz with order

In principle, such mixed modes may also be present in main-sequence stars but they are at too low frequency to be excited to observable amplitudes.

are expected to be roughly evenly-spaced in frequency, with a characteristic spacing known as the large separation