How big is the Solar System?

We find out how vast our solar neighbourhood really is

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The true edge of the Solar System stretches beyond the Kuiper belt. Image Credit: NASA

The true edge of the Solar System stretches beyond the Kuiper belt. Image Credit: NASA

Asked by Liam Knowles

This really depends on what you class as the Solar System. The distances involved are enormous so we work in Astronomical Units (AU), where one AU equals 150 million kilometres (93.2 million miles) and is the distance between the Earth and Sun. Meanwhile, ice giant Neptune orbits at a distance of around 30AU. Beyond this orbit we have the Kuiper belt, which contains dwarf planets such as Pluto and stretches out to a distance of about 50AU.

The true edge of the Solar System is defined by where the Sun’s gravity dominates and everything can be considered to orbit it. This rests beyond the Oort cloud, a sphere of icy objects at a distance of 100,000AU. To escape the dominance of the Sun’s gravity you would need to travel past this point.

Answered by Sophie Allan from the National Space Centre

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