Helioseismology

So apparently helioseismology is actually a thing. Basically the sun, a large blob of gaseous material, has modes of oscillation. The first is called solar breathing, and involves the sun expanding and contracting periodically. In essence, if the sun is slightly larger than its equilibrium size, then gravity can overwhelm the pressure forces, and it contracts. But then of course it overshoots and contracts too much, at which point pressure pushes it outwards again. Similarly, the second mode involves the sun starting slightly pancake-shaped. It then expands towards a sphere, overshoots into a moderately conical blob, and then rebounds to a pancake shape. There are a ton of these modes, and helioseismology is the study of what the modes can tell us about the internal structure of the sun. It's a really neat field, and has a seriously cool name to boot.