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Last Updated: Tuesday April 21 2009 11:59 GMT

Dimming sun baffles astronomers

The Sun

Astronomers say the Sun is the dimmest it has been for almost 100 years.

The Sun normally has an 11-year cycle when, at its peak, it has a boiling atmosphere that spits out flares and planet-sized chunks of super-hot gas.

Last year, the Sun was expected to start heating up towards its peak after a quiet spell in its cycle.

But pictures taken by space telescopes show that for a lot of the past year there have been no sunspots and very few solar flares.

Scientists say that's the longest time of inactivity since before the space age began, and no-one's sure what's causing it.

Professor Louise Hara of University College London, says the activity of the sun - or lack of it - is causing a big scientific debate.

"There's no sign of us coming out of it yet," she said.

"At the moment, there are scientific papers coming out suggesting that we'll be going into a normal period of activity soon.

"Others are suggesting we'll be going into another minimum period."