Two spacecraft that have been travelling for more than 33 years are about to become the first man-made objects to leave our solar system and enter the mysterious region outside.

NASA experts gave a presentation this week to update people on the progress of Voyager 1 and 2. Voyager 2 was launched into space on 20 August 1977, with Voyager 1 following a couple of weeks later.

Voyager 1 and Voyager 2 are now nearing the edge of the heliosphere. This is the name given to the ‘bubble’ of magnetic fields and electrically charged particles that the sun forms around itself, and which stretches up to three times wider than the orbit of Pluto.

Voyager 1 is the furthest man-made object from Earth, and is around 17.4 billion kilometres from the sun. The Earth is just 150m km away, on average. Voyager 1 is so far away that a signal travelling at the speed of light from controllers here on Earth still takes 16 hours to reach it. To the Voyager craft, our sun looks like a tiny speck of light.

The two craft are in the very outer ring of the heliosphere, known as the heliosheath. The edge of this bubble is known as the heliopause, and Voyager 1 and 2 are expected to cross this in 2015. Then they will enter the interstellar space, which has so far been unexplored by mankind.

Voyager 1 and 2 should be able to function until at least 2020. That is because they are both equipped with a nuclear fuel source.

Before they ventured towards the edge of our solar system, the two probes made a succession of amazing discoveries. They sent home evidence for volcanoes on Jupiter’s moon, Io, an ocean beneath the surface of another of Jupiter’s moons, Europa, and icy geysers on Triton, Neptune’s moon.

Their next incredible adventure began in 1980, when Voyager 1 used the gravity of Saturn as a slingshot to fire itself towards the edge of our region of space.

For some more cool facts, take a look at the NASA video below.