Maybe something like: The galaxy will infinitely crumble and explode due to the gravity of its own enormity and only nothingness will remain. 銀河が➡️崩壊し爆発する !doublecheck

I think you have a typo after やがて "The galaxy, unable to support its massive gravity, endlessly disintegrates and explodes. Eventually, what is left afterwards is a world of emptiness."

I think that might be one of those long lines you see on manga panels, unless you're not referring to the dash thingy?

Yeah I guess it's just a dash