Carl Edward Sagan (/?se???n/; SAY-g?n; November 9, 1934 – December 20, 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation. Sagan assembled the first physical messages sent into space, the Pioneer plaque and the Voyager Golden Record, universal messages that could potentially be understood by any extraterrestrial intelligence that might find them. Sagan argued the hypothesis, accepted since, that the high surface temperatures of Venus can be attributed to, and calculated using, the greenhouse effect.

Initially an assistant professor at Harvard, Sagan later moved to Cornell where he would spend the majority of his career. Sagan published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. Wikipedia