In September, NASA announced that its Voyager 1 spacecraft had entered interstellar space, becoming the first human-made object to travel beyond the heliosphere – the bubble of charged particles surrounding the Sun.
Although Voyager 1 has left our planetary neighbourhood, it’s still well within the Sun’s gravitational grasp. Some scientists maintain that the Solar System extends all the way out to the Oort cloud – a vast reservoir of comets that are loosely bound to the Sun. The spacecraft is expected to take roughly 300 years to reach the inner edge of the Oort cloud, and some 30,000 years to pass through.
The spacecraft’s radioactive power source will keep its instruments going until at least 2020, at which point NASA will start turning them off one by one. With its systems shut down, Voyager 1 will become a silent ambassador orbiting the centre of the Milky Way. In 40,000 years’ time it’ll be closer to another star (AC +79 3888) than our own Sun. But with no way of contacting Earth, this’ll be one milestone that Voyager 1 celebrates on its own.