Houghton Mifflin Harcourt
Harcourt: Biographies: Carl Sagan
A look at Carl Sagan, the man who brought the wonders of astronomy to the average person. Carl Sagan helped millions of people understand earth, the solar system, the universe and beyond. (In Spanish)
Wikimedia
Wikipedia: Carl Sagan
This encyclopedia article from Wikipedia provides a brief biography of Carl Sagan, the American astronomer who pioneered exobiology and promoted the Search for Extraterrestrial Intelligence (SETI), and science in general.
Other
Observatorio Arval: Clyde Tombaugh
This is a biography page for the American astronomer and discoverer of Pluto, Clyde Tombaugh.