The Sun is our local star - a nuclear reactor at the hub of the Solar System. Each second, the Sun loses four million tons of mass - energy that will keep the Sun blazing for another five billion years.

Of the nine planets, Mercury orbits on the inside track - the closest planet to the Sun. Baked and irradiated, Mercury is a cratered little world - a pristine record of the impactors that rained from space during the early Solar System.

Venus is Earth gone wrong - a lifeless planet with a dense and choking atmosphere and temperatures to melt lead. Constantly shrouded in cloud, Venus could once have been Earth's twin with oceans and continents, even simple life.

We live on the largest inner planet, third from the Sun and the first with a moon. Earth is lucky - at just the right distance from the Sun for life to evolve in the oceans, for green plants to produce breathable air and for humankind.

The Moon was probably formed when a body the size of Mars twice hit early Earth. The first collision was a glancing blow. The second, two days later, was a major impact that threw enough material into orbit to form the Moon.

A total eclipse of the Sun is the greatest spectacular in the Solar System. It happens when the Moon, which is 400 times smaller than the Sun, completely obscures the Sun, which is 400 times farther from us than the Moon.