Almost every day, the great antennas of NASA’s Deep Space Network turn to a blank patch of sky in the constellation Ophiuchus. Pointing at nothing, or so it seems, they invariably pick up a signal, faint but full of intelligence. The source is beyond Neptune, beyond Pluto, on the verge of the stars themselves. see captionIt’s Voyager 1. The spacecraft left Earth in 1977 on a mission to visit Jupiter and Saturn. Almost 30 years later, with the gas giants long ago seen and done, Voyager 1 is still going and encountering some strange things. Right: An artist’s concept of Voyager 1. ‘We’ve entered a totally new region of space,’ says Ed Stone, Voyager project scientist and the former director of JPL. ‘And the spacecraft is beaming back surprising new information.’ Before we reveal the surprises, let us discuss exactly where Voyager 1 is: Our entire solar system-planets and all-sits inside a gargantuan bubble of gas about four times wider than the orbit of Neptune. The sun is responsible. It blows the bubble by means of the solar wind. Astronomers call the bubble itself ‘the heliosphere’ and its outer membrane ‘the heliosheath.’ [diagram] Voyager […]

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