New data from Voyager 1 appears to suggest that the spacecraft has left the solar system.
The probe, sent to photograph and collect data about Jupiter and Saturn, left Earth 35 years ago.
Dr Lucie Green, a scientist at Mullard Space Science Laboratory of University College London, told the Today programme's Evan Davis that "a change in the material around the spacecraft would indicate whether is has left the solar system."
If spacecraft has left the solar system it would "mark a profound moment for our space exploration" she added, as it is the first time a man-made object will have escaped into interstellar space.
Get in touch with Today via
or text us on 84844.