Astronaut, designation, derived from the Greek words for “star” and “sailor,” commonly applied to an individual who has flown in outer space. More specifically, in the West, astronaut refers to those from the United States, Canada, Europe, and Japan who travel into space.

There are three types of astronauts in the U.S. space program: the commander/pilot, mission specialist, and payload specialist.

Many astronauts have a strong background in science, engineering, or medicine, allowing them to perform research experiments during missions.
Astronauts are assigned specific tasks during their missions, which can include studying celestial bodies, deploying satellites, or conducting experiments on the human body in space.