What will happen to Earth when the Sun runs out of energy

asks Mayastar:
A. It's believed that the sun will, one day in the far distant future (or about 7.5 billion years' time), use up all its nuclear fuel, expand to a vast size and engulf the inner planets - including Earth.

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But now there's a new theory, published in a recent issue of Astronomy & Geophysics, which suggests that Earth might survive.

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Q. Who came up with the theory
A. Astrophysicists at the University of Sussex have taken another look at the calculations about the end of the sun and come up with a different conclusion. It's understood that, when the hydrogen fuel runs out, stars such as our Sun expand until they turn into a 'red supergiant', hundreds of times bigger than their previous size.

However, the astrophysicists have come up with something no-one had taken into consideration before...

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Q. What's that
A. A small detail - the loss of mass and declining gravity of a red supergiant. Dr Robert Smith, Reader in Astronomy, explained that this was significant because, if it was taken into account, the earth's orbit would increase.

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Q. What does that mean
A. It means that the Earth's orbit would take it out of reach of the Sun's outer atmosphere by a vital margin while the Sun was going through its various phases.

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Q. So the Earth wouldn't be swallowed up
A. No.

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Hooray for us!
Erm, we wouldn't be here.

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Q. What do you mean
A. By the time that the Sun becomes a red supergiant, the surface of the Earth will have been too hot for anything to live on for a very long time.

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Q. So, how long have we got
A. Oh, about 5.7 billion years.

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Q. Enough time to plan our escape, then
A. You'd think so, wouldn't you. Dr Smith believes that survival capsules are the answer. There isn't anything suitable to live on in our own galaxy, and other planets are just to far away to hop to. He suggests building an international Space Station as the first step.

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By Sheena Miller