I'm looking for a cool and interesting subject in mathematical astrophysics to study for my master's project. What I really aim for is certain processes in the cosmos (multiple body-problem, black holes, asteroid belts, colliding stellar objects, etc...), but my background is not very much on the physics side, unfortunately. However, I read about special relativity, gravitational waves and how to measure in space, but not in a very mathematical way.
I would like to hear from someone whether they know similar subjects like the above that are reachable for a graduate math student, like me, to study for their master's project.
My background is mainly in algebra (Galois, Geometry, crypto), but I also have done statistical data analysis courses and (P)DE courses; thus I have seen a rich part of mathematics, but my specialty is really in abstract algebra. However, especially now, I would like to get to know subjects that are not mainly abstract algebra, but more PDE, for example.
I'm ready to dive into depths of mathematical physics if necessary. Thanks for any suggestions!