Passage: Purdue offers both undergraduate and graduate programs in over 211 major areas of study, and is well known for its competitive engineering curricula. The university has also been highly influential in America's history of aviation, having established the first college credit offered in flight training, the first four-year bachelor's degree in aviation, and the first university airport (Purdue University Airport). Purdue's aviation technology and aeronautical engineering programs remain among the most competitive aviation-specific programs in the world. In the mid-20th century, Purdue's aviation program expanded to encompass advanced spaceflight technology giving rise to Purdue's nickname, Cradle of Astronauts. Twenty-three Purdue graduates have gone on to become astronauts, including Gus Grissom (one of the original Mercury Seven astronauts), Neil Armstrong (the first person to walk on the moon), and Eugene Cernan (the last person to walk on the moon).

Question: How many astronauts have come from Purdue?
Twenty-three