The pioneers of astronomy and space exploration have advanced humankind’s understanding of the universe. These individuals include earthbound theorists such as Aristotle, Ptolemy, and Galileo. They also include those who put their lives on the line by traveling into the great unknown, such as Christa Corrigan McAuliffe and Buzz Aldrin. Readers will chronicle the lives of individuals positioned at the vanguard of astronomical discovery, laying the groundwork for space exploration past, present, and yet to come.