Carl Sagan was an American astronomer, astrophysicist, cosmologist, and exobiology pioneer. He is best known for his work on the television series Cosmos: A Personal Voyage, which popularized science and astronomy. Sagan was a strong advocate for the scientific method and was one of the first to propose the possibility of extraterrestrial life. He wrote extensively on the subject of exobiology, and his research helped to shape the field. Sagan's work has had a lasting impact on the study of exobiology and the search for extraterrestrial life.