In April 2011, NASA announced that the two Voyager spacecraft would soon be the first human-made objects to leave our solar system. While on their journey, each day the Voyagers send back this message, "Expect the unexpedted."

At this point the power left in Voyager 1 from the radioactive decay of a Plutonium 238 heat source was expected to keep it running until 2020.

Credit: NASA/JPL-Caltech