Jupiter, in true colors

The spacecrafts are traveling at a distance where the Sun is but a bright point of light and solar energy is not an option for electrical power.
The Voyagers owe their longevity to their nuclear power sources - known as Radioisotope Thermoelectric Generators, provided by the Department of Energy.

Voyager 1 is now at the outer edge of our Solar System, in an area called "The Heliosheath", such as the zone where the Sun's influence wanes. This region is the outer layer of the 'bubble' surrounding the Sun, and no one knows how big this bubble actually is. Voyager 1 is literally venturing into the great unknown and is approaching interstellar space.
Traveling at a speed of about 1,6 MKM per day (!), Voyager 1 could cross into interstellar space within the next 10 years.