Carl Sagan was an American astronomer, astrophysicist, cosmologist, author, and science communicator. He is best known for his work as a science popularizer and communicator, and he was also a highly regarded astronomer and astrobiologist. Sagan is credited with popularizing the term 'COSMOS' and the phrase 'billions and billions' in reference to the number of stars in the universe. He wrote several books, including the Pulitzer Prize-winning book, 'The Dragons of Eden'. He was also the host of the popular television series, 'COSMOS: A Personal Voyage'. Sagan was a professor of astronomy and space sciences at Cornell University from 1968 until his death in 1996.