Everything about the Solar System

The Sun is a star seen close up: a ball of glowing gas, layered like an onion, with a furnace in the middle.

With moving pictures and photographs

The Sun turns matter into light in its core. The light then takes many thousands of years to find its way out.

The Sun has weather: dark spots, sudden flares and vast eruptions that follow an eleven-year rhythm and can reach the Earth.

The Sun blows a thin wind past every planet. Far beyond Neptune the wind stops, and two spacecraft have crossed the place where it does.

The eight planets come in three sorts, and where each one formed explains which sort it is.

For 76 years the Solar System had nine planets. In 2006 astronomers agreed on what the word means, and Pluto no longer fitted.

With moving pictures and photographs

Seen from outside, the Earth is one rocky planet among four. It is also the only one with seas on its surface, and the only place known to have life.

With moving pictures and photographs

The planets grew from a disc of gas and dust around the young Sun, from specks to boulders to worlds, in a few tens of millions of years.

Nobody has been more than a scratch below the ground, yet earthquakes show what is inside the Earth. The moving metal at its centre makes a shield round the planet.

With moving pictures and photographs

Three rocky planets began much alike and ended as a furnace, a home and a frozen desert. The difference is their air.

All four giant planets have rings. They are countless separate pieces of ice and rock, each on its own orbit, and astonishingly thin.

Anything that orbits a planet is a moon. There are more than 400, from worlds bigger than Mercury to rocks a kilometre across.

Our nearest neighbour: a quarter as wide as the Earth, made from the wreckage of a collision, and the only other world people have stood on.

With moving pictures and photographs

Several icy moons hide seas of liquid water under their crusts, kept warm by tides. They are the likeliest places to look for life.

Some moons keep time with each other, lapping their neighbours in exact whole numbers. That rhythm heats Io, carves gaps in rings and makes two moons swap places.

Why there are two high tides a day, why the Moon keeps one face to us, and what keeps Io erupting.

Why the Moon changes shape every month, and why eclipses are much rarer than that.

Asteroids, comets and the icy bodies beyond Neptune are what was left over when the planets were made. Where each kind lives tells you what it is made of.

A comet is a small dark lump of ice and dust. Near the Sun it boils off a cloud bigger than a planet and tails millions of kilometres long.

A shooting star is a grain of dust burning up. Bigger pieces reach the ground, and once in a long while one is big enough to change the world.

Rocks from space have hit the Earth before and will again. We now watch for them, and in 2022 a spacecraft moved one on purpose.

With moving pictures and photographs

Far beyond the planets, a vast round shell of icy bodies is thought to surround the Sun. Nobody has seen it. Comets are the evidence.

An orbit is a fall that never reaches the ground. Newton's cannonball shows how.

With moving pictures and photographs

Three short rules that describe every orbit, found from years of watching Mars.

Near any two orbiting bodies there are five places where a small object can keep station. Telescopes are parked at two of them, and asteroids gather at two more.

Getting into space is about speed, not height. After that a spacecraft mostly coasts, and borrows speed from planets on the way.