After the preliminary examination is passed, students must register for a minimum of 3 credits, normally research (Astronomy 990), each semester.
In collaboration with your proposed major professor, you should begin considering a thesis topic before you take the preliminary examination.
Formal approval of the thesis proposal is obtained after you make an oral presentation to the faculty giving the thesis title; the aim of the research (together with a statement of how it is related to current results, research, and trends in astronomy), an outline of the specific steps to be carried out; and a preliminary estimate of the facilities required (e.g. time at observatories or supercomputer centers).
This approval should be obtained within nine months of passing the preliminary examination. After the finished thesis has been presented, the final oral examination will include questions on the thesis research and also its relation to the wider field of which it is a part.
For final submission to the graduate school, the thesis must adhere to the graduate school formatting guidelines.