Solar System

The star we call the Sun lies at the centre of the Solar System, an array of objects of various sizes that move around, or orbit, it. These are: the eight major planets (in order...

Sun

The Sun is a typical star, a spinning ball of hot gas made up almost entirely of hydrogen (three-quarters of its mass) and helium. To us it is of crucial importance since no life...

Sun A-Z

Asteroids

Circling the Sun, mainly between the orbits of Mars and Jupiter, are millions of small, planet-like objects called asteroids or minor planets. The largest, Ceres, discovered in...

Comets and meteoroids

A comet is a potato-shaped lump of dust and ice measuring only a few kilometres across, accompanied by—when near to the Sun—two tails stretching out hundreds of millions of...

Trans-Neptunian objects

A trans-Neptunian object (TNO) is any minor planet or dwarf planet in the Solar System that orbits the Sun at a greater average distance than Neptune. TNOs are classified into two...

Meteorites

A meteorite is a rock that originated in outer space and has fallen to the surface of a planet or moon. Thousands of meteorites, the vast majority tiny pieces of rock, crash to...

Comets and asteroids A-Z

Origins of the Solar System

The Solar System began forming about 4.5 billion years ago. Then it was just a small part of a vast cloud of gas and dust, measuring about 65 light years across, that drifted...

Evolution of the Solar System

The Solar System has not stayed the same since its formation, but evolved—changed over time. In its early years, the giant planets shifted their positions, moving nearer or...