Voyager 2 and scale of the Solar System, illustration. From left to right are: the Sun, its planets, the Voyager 2 spacecraft leaving the heliosphere, and the Oort Cloud. The scale is logarithmic, based on the Earth-Sun distance (1 astronomical unit, AU, 150 million kilometres). The scale markers increase in powers of ten, with Saturn at around 10 AU, the heliopause at around 100 AU, and the Oort Cloud boundaries from 1000 AU to 100,000 AU. The heliosphere is a protective bubble around the Sun, separating the planets from interstellar space. The heliosphere has a turbulent outer boundary known as the heliosheath. Voyager 2 (launched 1977) reached the inner boundary of the heliosheath (the termination shock) in August 2007. It crossed the outer boundary (the heliopause) in November 2018, passing into interstellar space. Voyager 2 will reach the outer regions of the Oort Cloud (the source of long-term comets) in around 30,000 years, and pass near the star Ross 248 in 40,000 years.