Who was the twentieth century astronomer?

The twentieth century saw many prominent astronomers, but one of the most notable was Carl Sagan. He was renowned for his work in planetary science and for popularizing science through books and television, notably the series "Cosmos." Sagan made significant contributions to our understanding of planetary atmospheres, particularly those of Mars and Venus, and advocated for the search for extraterrestrial life. His ability to communicate complex scientific ideas to the public has left a lasting legacy.