By Steve Connor - Science Correspondent.
An ambitious plan to look for intelligent life on other planets and peer into black holes with a radio telescope the size of 150 football [fields] emerged in Britain last week.
Scientists who met at Jodrell Bank in Cheshire, where the first radio telescope was built 50 years ago, said the new instrument would be hundreds of times more sensitive than today's most powerful telescopes.
Unlike the Hubble space telescope, it will be able to focus on extremely faint sources of radiation emanating from distant stars and galaxies. As a radio telescope, it will also exploit a far broader range of the radiation spectrum than Hubble, which detects only light.
The telescope, to be built over the next 15 years, will cover an area of 11 million square feet, and measure nearly three quarters of a mile across. It will be able to detect radio signals from about 15 billion light years away -- the outside edge of the universe. Because this radiation has taken billions of years to reach Earth, scientists hope it will provide new evidence about the Big Bang, the primordial explosion thought to have created the universe.
"This allows us to see these galaxies at the time when they were forming. We should be able to look back to 90% of the age of the universe. We don't know exactly what we'll find," said Dr. Robert Braun, an astronomer at the national astronomy foundation in the Netherlands.
Dr. Peter Wilkinson, a Jodrell Bank scientist who helped to organise last week's summit, said one of the more ambitious objectives was to search for any artificial radio signals emanating from the broadcasts of intelligent lifeforms on other planets.
Present radio telescopes would only detect strong alien transmissions that were deliberately sent in the direction of Earth, said Wilkinson. "If you had an enormous telescope then you could pick up other transmissions, for instance if they had radio or TV broadcasts. If other civilisations had a big telescope looking at us they could tell there is something unnatural here just by our radio and TV broadcasts."
Dr. John Dreher, and American astronomer involved in the search for extraterrestrial intelligence, said the new telescope would be sensitive enough to detect TV-like broadcasts of alien life living between 10 and 20 light years away. The giant telescope will eventually be linked electronically to smaller radio telescopes in orbit around Earth to create a network of radio telescopes with an even wider collecting area. This will enable astronomers to separate two distant sources of radiation that are so close as to be indistinguishable with conventional telescopes on Earth.
Wilkinson said one of the most important objectives of the new telescope was to search for black holes, intensely violent areas formed by collapsed stars with such strong gravitational fields that all nearby matter and even light is sucked in. "We want to find out whether there is a black hole at the centre of every galaxy, including our own," he said.
Traditional optical instruments, such as the Hubble telescope, are hampered in their search for black holes by massive dust clouds which obscure their view. Unlike light, however, radio waves can penetrate dust, enabling radio telescopes to "look" inside black holes.
Because the new telescope will be 200 times bigger than Jodrell Bank, strikingly different technology will have to be applied. Instead of one giant steel dish, scientists envisage hundreds or even thousands of dishes, each computer-controlled to focus on the faintest radio waves from distant starts.
Some scientists believe the telescope should be sited in Britain, because of its distinguished history of radio radioastronomy, dating back to the discovery of radio waves in space by Sir Bernard Lovell in 1947. Others favor rural central Europe or the desert of the Australian interior, where there is less risk of radio interference from built-up areas.
The astronomers who met last week will draw up a detailed financial proposal over the next two years. [Building] the instrument... will come about through international collaboration, as the project is too big for any one country.
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