Voyagers update
Wow! Cosmic radar!
The bursts were probably generated when clouds of solar material, hurled by the sun during an unusually stormy period in April 2001, rammed into cold interstellar ions at the edge of the solar system, says Donald A. Gurnett of the University of Iowa in Iowa City. Radio bursts from that collision then traveled back toward the sun and were intercepted by Voyager 1. From the speed of the clouds and the time it took them to reach the heliopause, Gurnett's team calculated the distance to the edge.