Voyager 1 has recently crossed the boundary of our solar system and passed into interstellar space, and Voyager 2 is likely to follow suit, on a different path, between 2016 and 2017. The two Voyager probes will continue to transmit details of discoveries beyond our solar system until at least 2020.
Dr Christopher Riley is a broadcaster and film-maker specializing in history and science documentaries. In 2004 he won the Sir Arthur Clarke award for the BBC1 blockbuster series Space Odyssey: Voyage to the Planets. His film In the Shadow of the Moon: The Story of the Apollo Astronauts, won the World Cinema Audience Award in 2007.