At the edge of the heliosphere, you wouldn't know by looking whether you left the cradle of humanity behind and floated out into interstellar space. You would just see unfathomably empty space, no matter which side of the invisible line you were on. But scientists now have strong evidence that NASA's Voyager 1 probe has crossed this important border, making history as the first human-made object to leave the heliosphere, the magnetic boundary separating the solar system's sun, planets and solar wind from the rest of the galaxy. "In leaving the heliosphere and setting sail on the cosmic seas between the stars, Voyager has joined other historic journeys of exploration: The first circumnavigation of the Earth, the first steps on the Moon," said Ed Stone, chief scientist on the Voyager mission. "That's the kind of event this is, as we leave behind our solar bubble."
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Study: Voyager 1 left heliosphere around August 25, 2012
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Voyager 1 and 2 were launched in 1977, 16 days apart
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Voyager 1 is now the first mission to explore interstellar space
Both @placeholder probes carry time capsules known as "the golden record," a 12-inch, gold-plated copper disc with images and sounds so that extraterrestrials could learn about us.