A NASA satellite an incredible 9 BILLION miles from earth has just told scientists it has fired thrusters which will allow it it leave the solar system for interstellar space.
Voyager 2, which was launched in August 1977 and is still functioning despite the mind boggling distances and numbers involved, has set course for the star Sirius.
When it flies past Sirius, in a mere 296,000 years, mankind will have become extinct, or will have evolved into an entirely different species. (The satellite's sister craft Voyager 1 will wander interstellar space for just 40,000 years before it passes by the star AC+79 3888, in the constellation of Camelopardalis.)
Already Voyager 2 is 9 billion miles (14 billion kilometers) from Earth at the edge of the heliosheath where our sun finally runs out of steam.
In this outermost layer of the heliosphere the solar wind, which streams out from the sun, is slowed by the pressure of interstellar gas.
NASA engineers sent the instruction to Voyager 2 on November 4 but even travelling at the speed of light it took 14 hours to reach the satellite.
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 at least another decade.
Voyager 1 and Voyager 2 are each equipped with six sets, or pairs, of thrusters to control the pitch, yaw and roll motions of the spacecraft.
These include three pairs of primary thrusters and three backup, or redundant, pairs. Both spacecraft are now using all three sets of their backup thrusters.
As Voyager 2 powers up its backup thrusters and continues on its journey into the unknown, both craft are entering the final stages of their lives as functioning spacecraft, capable of relaying information back to Earth.
However, when launched in 1977, each spacecraft carried a gold-plated audio-visual disc containing photos of the Earth, scientific information and greetings spoken from people from around the world.
Frozen, in the vacuum of space, both spacecraft and their contents need not fear decay and, provided they do not collide with any stellar objects, will go on to wander the stars for billions of years.