Image credit: NASA
Thirty years ago yesterday, NASA launched the Voyager 2 space probe on a journey to visit the outer solar system. Two weeks later, its twin, Voyager 1, was launched on the same voyage. (I don't know why Voyager 2 was launched before Voyager 1.) The two spacecraft jointly explored Jupiter and Saturn; Voyager 1 was sent on a special mission to Jupiter's inner moons, and so headed away from Saturn in the wrong direction to tour any other planets. But Voyager 2 continued on, becoming the only probe to visit Uranus and Neptune. I remember watching images from Neptune coming in live on CNN back in 1989.
Since that time, both Voyagers have remained alive and alert, heading outward at over ten miles per second. Voyager 1 is now 100 times further from the sun than the Earth, nearly ten billion miles away; Voyager 2 is a little closer, a mere eight billion miles away. Both spacecraft will leave the Solar System forever and head out into the Milky Way galaxy for eternity, though it will be tens of thousands of years before either Voyager comes within two light-years of another star. Given that we haven't found all of the mountain-sized asteroids in our own solar system yet, it seems highly unlikely that any civilization that might be around these other stars would even notice the passing of a human-sized lump of metal that long-since stopped operation.
In the meantime, the Voyagers are working on one final science goal before their electricity generators die (around 2020). They are looking for the boundary between the sun's wind and interstellar space -- sort of like the boundary between Earth's atmosphere and space. This boundary, called the heliopause, means that the Voyagers will have essentially left all influence of the Sun (other than gravity strong enough to keep some comets and Kuiper Belt Objects around), and the Voyagers' true interstellar voyage will have begun.