On Jan. 28, 1986, America witnessed a tragedy: the explosion of Space Shuttle Challenger in the blue skies over Florida. The doomed shuttle touched us like we have never been touched before because along with the tragic loss of astronauts, a teacher was on board.

NASA's space shuttle Challenger completed 10 missions before it broke apart during a launch in 1986, killing seven astronauts.

Wednesday marks a somber anniversary in American history. 40 years ago, seven astronauts were killed when Space Shuttle Challenger exploded during liftoff.

Christa McAuliffe trained to be the first teacher in space, preparing to turn a shuttle cabin into the most-watched classroom in America. Forty years after she and six crewmates died when Challenger broke apart shortly after liftoff,

Forty years ago, Americans were shocked when the space shuttle Challenger exploded 73 seconds after it launched on a chilly day in Florida.