I found this interesting

Is it better to go into the military or to a university to become an Astronaut?

Astronauts fall into two categories, Pilots and Mission Specalists.

Pilot Astronauts are all former military pilots, most have test pilot experience. This is because a lot of what pilot astronauts do is flying test vehicles. The Space Shuttle is almost 30 years old, but before that the Mercury, Gemini, and Apollo programs were all developing the spacecraft as they went along.

The Pilot Astronauts mostly have advanced degrees as well. They are engineers to start with, pilots on top of that (most with combat experience) and then they often pick up another advanced degree just to make them more competitive. Buzz Aldrin was the first astronaut to have a doctorate, he did his doctoral thesis on orbital mechanics and how two space ships could link up and dock.

Mission specalists are people who are associated with a particular bit of cargo the Shuttle is going to fly. Sometimes they are scientists who come with a particular experiment. Some of them came from private industry back when NASA was trying to use the shuttle as a vehicle to launch private satilites... they would come with the satilite. Some of them come from the military if the Shuttle is doing a classified mission (which they don't do any more... Shuttle is too unreliable for the USAF.) Some of them are "stunts" like taking up a Senator to get support for NASA in Congress, or when they took up John Glenn to get publicity, or the teacher in space deal.

The university that produced the most astronauts is the United States Naval Academy. In second place is a civilian school... I think it is a state school in Ohio but I don't recall.

Check this link out for what is expected of an astronaut