Voyager approaching solar system's final frontier: "NASA's Voyager 1 spacecraft is about to make history again as the first spacecraft to enter the solar system's final frontier, a vast expanse where wind from the Sun blows hot against thin gas between the stars: interstellar space. However, before it reaches this region, Voyager 1 must pass through the termination shock, a violent zone that is the source of beams of high-energy particles."