Since taking flight in 1977, the Voyager spacecraft continue to make important discoveries. Decades after launch, the twin spacecraft are revealing secrets of the interstellar medium: the tenuous material that fills the vast space between the stars. 

The news feature in the scientific journal Proceedings of the National Academy of Sciences, features Donald Gurnett, professor emeritus in the Department of Physics and Astronomy at Iowa, who has been involved with the Voyager mission since its beginning.