Page last updated at 09:27 GMT, Friday, 5 March 2010

Revel in the wonder of the Solar System

By Danielle Peck
Series producer, Wonders of the Solar System

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Revel in the wonder of the Solar System

There are maps you can buy which show how light pollution blocks out the night skies. Look at the map for the UK, and English star-gazers have it the worst.

It would take a trip to a few scattered oases in Northumberland, East Anglia or the West Country to see the skies anything like our ancestors once enjoyed.

We are more divorced than ever from the celestial backdrop that once held us in awe. But there is one astronomical event, perhaps the most precious wonder of the Solar System, where even the most dazzling night sky won't be an advantage.

July 2009 saw the longest total eclipse of the Sun this century.

It was always going to be a centrepiece moment for the BBC's new series Wonders of the Solar System, but deciding where to go to film it was a nerve-wracking gamble.

As the Moon drifted slowly across the face of the Sun and darkness fell, I became aware that I was standing on a ball of rock orbiting a star
Prof Brian Cox

The shadow cast by the Moon would make landfall on the west coast of India, track across the north of the country and on to Bangladesh, Nepal, Bhutan, Myanmar and China, before skimming off across the Pacific Ocean.

In theory a rich choice of filming locations, but July is peak monsoon season, with heavy cloud cover giving at most a 50% chance of capturing this spectacular event on camera. In the end, the gamble was even greater.

'Precious and powerful'

A decision was made to film in Varanasi, the Indian city on the Ganges rooted in Hindu worship including the Sun god, Surya.

It would provide a dramatic setting for the event but reduce the odds even more - the predictions were a greater than 70% chance of cloud.

Dawn broke with overcast skies, but just before the moon started to slip in front of the Sun, they cleared. Presenter of the series, Professor Brian Cox, remembers the moment well:

"I knew that a total solar eclipse is one of the most precious and powerful astronomical events, but I wasn't prepared for the profound sense I felt of our place in space.

"As the Moon drifted slowly across the face of the Sun and darkness fell, I became aware that I was standing on a ball of rock orbiting a star, surrounded by other balls of rock and gas drifting in an immense sea of black.

"We're only a chance astronomical event away from the wondrous desolation just a few miles above our heads."

It was only when the Moon perfectly covered the disc that Brian and the thousands of spectators thronging the banks of the Ganges witnessed a new facet of the powerhouse of the Solar System.

Aurora (Nasa)
The "curtains of light" that make up the Aurora Borealis

The breath of the Sun - the solar wind - could be seen streaming away into space at the beginning of its epic journey.

The solar wind is a stream of smashed atomic particles that scythe through the vacuum of space at supersonic speeds.

As it passes Earth, the solar wind leaves its mark in magical displays of auroral lights that circle both Poles.

Recently we have witnessed even larger auroral lights around the great gas giant planets, Saturn and Jupiter, as the solar wind battles with the magnetic fields surrounding these immense, chaotic worlds of gas.

The solar wind pushes out into space, creating a vast bubble surrounding the Sun called the heliosphere.

Beyond lies interstellar space. Up until now, this bubble surrounding the Sun, called the heliosphere, has been largely theoretical but mankind is on the verge of crossing the boundary of this bubble and leaving behind the empire of the Sun.

More than 30 years ago, the two Voyager spacecraft were launched on the Grand Tour - a mission to explore the outer planets of the Solar System.

They passed Neptune (now officially the outermost planet) back in 1989, and have kept travelling away from the Sun at over 60,000km/h ever since.

Deep journey

Project scientist Dr Ed C Stone has been on the Voyager team since before the probes were launched in 1977.

"When I started on Voyager, my two daughters were young and by the time they were in college we were already past Saturn, on our way to Uranus. My daughters got married and Voyager just kept going. We had grandchildren, and Voyager just kept going," Dr Stone says proudly.

Voyager - Artist's impression (Nasa)
The Voyager probes just keep on going

"It's wonderful being part of a mission that's still exploring when it's 33 years old. Still going somewhere no spacecraft has been before."

Each year the probes travel more than three times the distance the Earth sits from the Sun. For 33 years, they have been travelling with the solar wind. They still haven't left behind the realm of the Sun - but they're getting close.

The probes regularly check in to the Deep Space Network, a communications system that helps Earthbound astronomers keep in touch with their robotic counterparts.

Now the probes are about 16 billion km away from Earth. At that distance, messages take 15 hours to get here, and recently those messages have started to say something particularly exciting.

The probes have detected a noticeable change in the behaviour of the solar wind - the first signs that it is being pushed back by the interstellar medium that permeates the Milky Way galaxy.

The Voyager probes have told us they will soon break through the heliosphere.

It will be the first time a manmade object has crossed into interstellar space, but the Voyagers' heroic journey will not end there.

The probes have enough power to keep doing some kind of scientific work until at least 2025. By then, we will have entered a new age of exploration.

The age of interstellar space travel.

You can see the first part of Wonders of the Solar System with Professor Brian Cox on BBC Two this Sunday 2100 GMT



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