This NASA file image shows a true color photo of Saturn assembled from images collected by Voyager 2. HO/AFP/Getty Images hide caption

itoggle caption HO/AFP/Getty Images

A bubble in space: Abell 39 marks the death of a star like the sun. Wind from the aging central star pushes into the surrounding interstellar gas, building up a dense shell that glows blue in this image. After 36 years of travel, the Voyager spacecraft is just now reaching the edge of the sun's own wind-blown bubble. WIYN/NOAO/NSF hide caption

itoggle caption WIYN/NOAO/NSF

This artist rendering provided by NASA shows Voyager 1 at the edge of the solar system. AP hide caption

itoggle caption AP