Stephen Hawking discusses the "Breakthrough Starshot" space exploration initiative during a news conference Tuesday at One World Observatory in New York City. Bryan Bedder/Getty Images for Breakthrough Prize Foundation hide caption

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Stephen Hawking's Plan For Interstellar Travel Has Some Earthly Obstacles
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This NASA file image shows a true color photo of Saturn assembled from images collected by Voyager 2. HO/AFP/Getty Images hide caption

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Exploring The Solar System Through The Eyes Of Robotic Voyagers
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A bubble in space: Abell 39 marks the death of a star like the sun. Wind from the aging central star pushes into the surrounding interstellar gas, building up a dense shell that glows blue in this image. After 36 years of travel, the Voyager spacecraft is just now reaching the edge of the sun's own wind-blown bubble. WIYN/NOAO/NSF hide caption

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This artist rendering provided by NASA shows Voyager 1 at the edge of the solar system. AP hide caption

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Has Voyager 1 Left The Solar System?
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