We watched in awe as an object the size of Mars approached the Earth, crossing space on a collision course at over 30 kilometres a second.

Watch the openning sequence of The Planets

It was graceful yet purposeful and unstoppable as it splashed down on the early Earth, causing a complete meltdown of the young planet and hurling debris out into a spiral around it.

But this cosmic catastrophe was all in the silicon belly of a supercomputer in West London.

The series runs over eight episodes

For the past two years in scattered, anonymous buildings across the capital, a large team of talented animators and FX wizards have been working round the clock to bring the Solar System in all its glory to our television screens.

The result is The Planets, a breathtaking new BBC Science series that will air in the UK from Thursday, 29 April.

Distant worlds

That there were 63 moons in our Solar System was a fact that Series Producer David McNab admits to not knowing when we set out to make The Planets.

He's even happy to confess that he didn't know how many planets there were! But getting to grips with the geography of our cosmic neighbourhood was only the first step towards bringing these distant and diverse worlds to a wider audience.

The shortage of real film meant the BBC had to turn to visual effects

We soon realised that there is precious little film of the planets in the vaults of the world's space agencies. "The only real movie pictures to come from the space race were beamed back from Apollo," says David.

"Most of the probes just carried crude still cameras."

And we'd dreamt of flying through the lethal radiation fields of giant Jupiter and taking an impossible journey along the rivers of plasma that encircle the Sun.

So to make it happen, we knew we'd have to try some ingenious tricks.

Searing flames

Rita Kunzler and The Planets visual effects team recreate the surface of the Sun

You could see your breath in the big hanger in Acton, but things were about to get much hotter. The seething surface of the Sun was about to come to life as BBC visual effects expert Paul McGuiness ignited his flame thrower and began to torch the false ceiling a few metres above.

Directly beneath the searing roof, high-speed cameraman Peter Tyler had carefully covered his precious Miliken camera in protective glass and asbestos blankets. "Action," shouted FX director Alan Marshall.

Our Solar System has been billions of years in the making

The camera motor began to scream as it dragged the film through its shutters at 400 frames per second.

Back in the office, artist Rita Kunzler would use all her skills to metamorphose the slow-motion flames into the surface of the Sun. "The trick was to give this relatively small scale flame a larger, grander feel.

"It had to feel like it was the surface of a star a million miles across," she explains. She tiled the flames into a blazing montage and then wrapped them over a sphere. The Sun shone.

Spitting sulphur

Behind Rita sat Yugoslavian computer animator Aleksandar Stiglic. Using state-of-the-art software, he was creating the alien terrains of Mars, Mercury and the icy moons of the outer Solar System. He could make volcanoes that spat sulphur into space, canyons the size of continents, and craters as vast as countries.

Aleksandar Stiglic makes Mars come to life

"Building terrains is tough," says Aleksandar. "The human eye is very discerning. You don't need to be an expert to instantly spot a fake terrain". He took some of Nasa's terrain maps and then made textures for them by combining different elements from libraries of rock surfaces. Aleksandar's greatest challenge was to bring alive the giant Martian canyon Vallis Marineris.

"It was difficult to convey the size of this landscape without a scale reference," says Aleksandar. "So in the end, we made a four-shot sequence out of the original single shot story board, rising slowly out of the network of valleys from different heights until we were almost in orbit with a view of the whole canyon system".

The giant Vallis Marineris

It took two years to turn The Planets from a paper proposal into reality. When we started making the series, there were 11 planets known outside the Solar System and only one planetary system - ours.

By the time we finished, astronomers had discovered 18 more planets orbiting other stars and the first extra-planetary system other than our own orbiting the star Upsilon Andromedae.