China Unveils World’s Largest Radio Telescope   Leave a comment


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BBC

Nestling in a vast natural crater, China’s giant is about to come alive.

A colossal, steeply curved dish glints in the sunlight, surrounded by jagged mountains that cut into the sky. Construction workers, busy putting the finishing touches to this structure, look tiny against the huge backdrop. This is the largest radio telescope ever built, measuring 500m (1,640ft) across.

“In China, in astronomy, we’re far behind the world,” says Prof Peng Bo, the deputy project manager of the Five-hundred-metre Aperture Spherical Telescope – or Fast for short.

We used to have to go abroad, to use telescopes outside China. I think it’s time for us to build something in China.”

Situated in Guizhou Province, in the south-west of the country, Fast dwarfs all other radio telescopes.

The former record-holder was the Aricebo Observatory, in Puerto Rico, with a diameter of 305m (1,000ft).

The Lovell telescope at Jodrell Bank in the north of England measures 76m (249ft) across.

This isn’t simply one-upmanship – bigger really is better when it comes to radio astronomy.

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While some telescopes, such as the Hubble Space Telescope, use light to see the visible Universe, a radio telescope is more like a giant ear “listening” for radio waves emitted by objects in deepest space.

Like light, radio waves are a form of electromagnetic radiation – but they have extremely long wavelengths, ranging from about a millimetre to more than 100km in length.

And because these cosmic signals have travelled for great distances in space they are also incredibly weak.

This is why radio telescopes need to be big – the larger the dish, the more signals it can collect.

China’s new telescope is so large that the team hopes it will pick up radio waves from the far reaches of the cosmos.

The telescope will be searching for ancient signals of hydrogen – one of the building blocks of the early Universe – to try to understand how the cosmos evolved.

It will also be hunting for new stars – in particular a rapidly rotating and extremely dense type of star called a pulsar – and it will even join the hunt for extraterrestrial life.

“The search for extraterrestrial life is a very hot topic for every telescope – and also for the public. I think Fast can make a contribution,” Peng says.

It took 10 years of trawling through satellite images of the Chinese countryside to find a natural depression big enough to fit the telescope inside.

But construction has taken place in record time – just over five years, and it’s nearly complete.

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Posted May 24, 2016 by markosun in Science, Space

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