Since this is the first time around, I’ll start by combining two questions, one from Sashin Ranasinghe, “What is astrophysics?” and from Tom Riecken, “what do I do?”
In a broad sense, astrophysics is the application of physics (and a bit of chemistry) to figure things out about the universe. Regular (experimental) physicists do experiments here on earth to figure things out, and astronomers observe what is happening out beyond earth. An astrophysicist takes what we know about physics and tries to create models that accurately describe what astronomers observe. There is often a bit of overlap in that astronomers sometimes do physics, but that’s the general idea.
As for what I do, my early work studied black holes and how they may have formed in the early universe. That work was mainly math-based, and not really computational. Since then I’ve started to shift to smaller scale computational astrophysics. Things like analyzing starspots and planetary eclipses, or few-body motions of stellar clusters.
Here “smaller scale” means I can do most of my work on a desktop computer. For bigger things my university has a cluster of computers, but there is a great deal you can do just with a good desktop. This has the additional advantage that you don’t need a huge grant to do research, just a computer and some time.
Right now the bulk of my research time is focused on finishing a textbook on computational astrophysics. I hope to have the thing finished by the end of Summer, which is when Cambridge wants the manuscript in.