The Solar System: the planets in order, their sizes and distances

What's in the Solar System

At the centre is the Sun, a star that holds 99.8 per cent of all the Solar System's mass. Round it go the eight planets, then the dwarf planets (Ceres in the asteroid belt; Pluto, Haumea, Makemake and Eris beyond Neptune), the moons (more than 400 are known, most of them round Saturn and Jupiter), and countless asteroids and comets.

The planets come in two families. Mercury, Venus, Earth and Mars are small rocky worlds close to the Sun. Past the asteroid belt come the giants: Jupiter and Saturn, made mostly of hydrogen and helium, and Uranus and Neptune, the ice giants. All four giants have rings, though only Saturn's are bright enough to see easily.

The planets in order

From the Sun outwards: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. A sentence to remember them: "My Very Easy Method Just Speeds Up Naming" (one word for each planet's first letter).

A "day" here is sunrise to sunrise. Venus is the odd one out: it spins so slowly, and backwards, that one spin takes longer than its whole year.

How far apart they are

Distances in space are so big that astronomers use the astronomical unit (AU): the distance from Earth to the Sun, about 150 million km. Neptune is about 30 AU from the Sun. Light, the fastest thing there is, takes a while to cross that:

A model you can picture

Pictures of the Solar System squeeze everything together to fit on a page. Here is what it would look like with everything shrunk by the same amount:

That's why space is mostly empty. Planet Dash lets you switch between a "friendly" scale (so everything fits on your screen) and the real scale, where you can fly for a long time between worlds.

How the planets move

Every planet goes round the Sun in the same direction, on a path called an orbit, nearly in the same flat plane. The closer a planet is, the faster it goes: Mercury takes 88 days to go round once, Neptune 165 years. Most planets spin the same way too; Venus spins backwards and Uranus rolls round on its side.

Because the planets move at different speeds, where they are changes every day. Planet Dash works out each one's real position for today from NASA's published orbits, so you can see where they all are now, and run time forwards or backwards to watch them move.