Our Solar System

The Solar System is our local region of space comprising the Sun and the objects that orbit around it. This includes the eight major planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune) and their moons, the asteroid belt, the Kuiper belt and other orbiting bodies such as dwarf planetscomets and planetesimals.

(N.B. until 2006, Pluto was considered to be a planet. However, it has now been reclassified as a dwarf planet.)

The Oort cloud – a spherical swarm of planetesimals – is believed to extend out to a distance of between 50,000 to 200,000 AU, the outer limit of which defines the edge of the solar system.

Between 99.8 and 99.9 percent of the mass of the solar system is contained within the Sun itself. However, the rest of the solar system doesn’t orbit the point at the centre of the Sun. The entire solar system, including the Sun itself, orbits the combined centre of mass of every body in the solar system. This centre of mass is known as the barycentre, and it shifts over time depending on how the mass of the solar system is distributed, although its position relative to the centre of the Sun is dominated by the four largest planets, Jupiter, Saturn, Uranus and Neptune. Despite the mass of the Sun being so large in comparison to the rest of the solar system, the barycentre actually lies outside of the surface of the Sun more than 50 per cent of the time.

The Solar System to scale
The Solar System to scale – 1 pixel = 0.02 AU

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Astronomy, Cosmology, Space and Astrophysics