(Photo: AP) The space shuttle Challenger explodes 73 seconds after launch, killing all seven astronauts aboard, including Christa McAuliffe, intended to be the first teacher in space. Other astronauts killed were Francis "Dick" Scobee, Michael J. Smith, Ellison S. Onizuka, Judith A. Resnik, Ronald E. McNair and Gregory B. Jarvis. Pictured: Astronauts Smith, Scobee, McNair, (l-r back); Onizuka, McAuliffe, Jarvis and Resnik.