Year in Review: Voyager 1 reaches interstellar space

Planetary probe is first to pass beyond heliosphere

GOING THE DISTANCE  Voyager 1 is the first human-made object to break out of the heliosphere.

JPL-Caltech/NASA

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When Caltech’s Ed Stone watched the launches of Voyager 1 and Voyager 2 from Cape Canaveral in 1977, he had only a glimmer of hope that either probe would survive to reach interstellar space.