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Voyager

NASA undated handout image shows an artist's concept of the Voyager 2 spacecraft. Voyager 2 has successfully switched to the backup set of thrusters that controls the roll of the spacecraft. Deep Space Network personnel sent commands to the spacecraft to make the change on November 4 and received confirmation on November 14 that the switch has been made. The change allows engineers to reduce the amount of power that the 34-year-old spacecraft needs to operate by turning off the heater that keeps the fuel to the primary thrusters warm. Although the rate of energy generated by Voyager 2's nuclear power source continues to decline, by reducing its power requirements, engineers expect the spacecraft can continue to operate for another decade. Voyager 2 is currently located about 9 billion miles (14 billion kilometers) from Earth in the heliosheath -- the outermost layer of the heliosphere where the solar wind, which streams out from the sun, is slowed by the pressure of interstellar gas. REUTERS/NASA/JPL/Handout

NASA's Voyager probes

Nasa's Voyager 1 spacecraft and its sister probe Voyager 2 have been traveling through space since

1977. Voyager 1 — the farthest-flung object created by human hands — has left the solar system forever, a study suggests.