Voyager Spacecraft Prepares to Exit the Solar System

Into the great unknown, into the wild blue yonder, past the second star on the right and straight on till morning: That's where NASA's Voyager 1 is heading. The remarkable spacecraft was launched 33 years ago, and it's now reaching the edge of our solar system. Within a few years, NASA says, it will enter interstellar space. Phil Plait reports on how researchers realized they'd reached a milestone in Voyager 1's journey: