Our solar system was a tempestuous place in its early days, with asteroids smashing into planets left and right and aliens stopping by to seed life on Earth. But before all that, simulations have shown that there may have been an extra ice giant in the mix, until Jupiter stepped in and flung it off into interstellar space.

In about five years, the 33-year-old Voyager 1 spacecraft will be the first man-made object to leave the Solar System. Five years might seem long on Earth, but when you're an object drifting through space for decades, it's relatively quick.