After 36 years, NASA's twin Voyager spacecraft are still going strong and still sending home information. Voyager I, the younger twin, is fast approaching the heliosheath, the very edge of our solar system. (The bubble of the heliosheath is grey in this artist's conception.) Beyond the heliosheath are the unexplored reaches of the interstellar medium. Outer space!
Image courtesy NASA/JPL-Caltech