Top 10 Scientific Discoveries of 2013

Voyager I Makes It to Interstellar Space
Artist's concept of the wondrous and wide-ranging Voyager spacecraft in flight Image courtesy NASA/JPL

It's going, going, gone.

NASA hit the longest home run of its career when Voyager 1, like the Pioneers 10 and 11 spacecraft, said sayonara to the planets of our solar system and the sun's gravitational influence. Voyager 1 is now streaking through interstellar space sending information back to Earth. Although the craft said bon voyage in August 2012, it wasn't until September 2013 that scientists were sure it actually happened.

It was a remarkable event more than 36 years in the making. Voyager 1 left Earth in 1977 for Jupiter and Saturn and scampered past the so-called heliosphere, the boundary of the solar system where the sun's gravity has little effect. When scientists made the shocking announcement, the craft was 11.7 billion miles (18.8 billion kilometers) from Earth. Voyager 2 also is headed for interstellar space.

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