Why not, erm, just call it astrophysics. It's not a good start for a career that involves equations not to cancel out one of the physics.
They don't cancel out, it's (1 + Astro)physics
Or Astro(physics2)
Naa.
That gives you too much physics.
That gets you astro.physics.physics
What you want is astro.physics + physics
Like wot cygnet did post.
This is why I don't have a PhD that includes math, but they really should just call it
astro, on account that it sounds cooler.
I'm still going to argue that one of those physics is redundant, I'm sure you can't do astrophysics without physics. From recently riffles through the CV pile, it does seem you can't do singular degrees these days, as though one broad subject is not enough.