astronaut

An astronaut is a person trained to command, pilot, or serve as a crew member of a spacecraft. The term comes from Greek roots meaning “star sailor” and is commonly used to describe space travelers who fly on missions organized by national or international space agencies.

Astronauts are typically selected through competitive programs run by agencies such as NASA (United States), Roscosmos (Russia), ESA (Europe), JAXA (Japan), and CNSA (China). Training lasts several years and includes flight training, engineering studies, physical conditioning, survival skills, simulators, and training for extravehicular activity. Individuals may specialize as pilots, mission specialists, or commanders, and may develop expertise in robotics, life support systems, or payload operations.

On missions, astronauts conduct scientific experiments, operate spacecraft systems, assemble or repair structures, and perform spacewalks. They must be adaptable to long durations away from Earth and to living in confined, technologically complex environments.

Related terms reflect national programs: cosmonaut is used in Russia, and taikonaut in China. In addition to career astronauts, some programs have spaceflight participants or space tourists who receive training but are not professional astronauts.

Notable milestones include Yuri Gagarin’s first human spaceflight in 1961, Alan Shepard’s first American in space the same year, and Valentina Tereshkova as the first woman in space in 1963. Since then, numerous crews have expanded human presence in low Earth orbit and beyond.

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