BEIJING - China will start construction on a 500-meter aperture spherical telescope, the largest in the world, in Southwest China's Guizhou province next month, said Yan Jun, head of the National Astronomical Observatories of the Chinese Academy of Sciences, on Friday.

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Costing some 700 million yuan ($106 million), the telescope will stand in a huge natural hole, the Karst depression, which is as large as 30 football fields, said Yan, a member of the National Committee of the Chinese People's Political Consultative Conference.

He said the Karst valley in Pingtang county of Guizhou province is the perfect place to build the huge bowl-like astronomical instrument.

"If the hole were filled with water, there would be enough water there for every person on Earth to get a bottle," he said.

The project is expected to be completed in five years, he said.

Once the telescope is put into use, astronomers will be able to observe things that are believed to be 11 billion light-years away, or on "the edge of the space", he said.

It will help astronomer observe galaxies and pulsars and find answers to questions about the origin of the universe and similar topics, Yan said.

Foreign astronomers and scientists are welcome to use the facility, he said.

The world's largest radio telescope is now the 300-meter Arecibo radio telescope developed by the United States.

A Xinhua report in 2008 cited Nan Rendong, a researcher at the National Astronomical Observatories, as saying that the new telescope's overall capacity will be 10 times greater than that of the Arecibo radio telescope in the US.

The report also said the telescope will be a highly sensitive passive radar capable of monitoring satellites and space debris, which will be a benefit to China's ambitious space program.

It suggested the construction of the telescope will start in 2008 and be completed in 2013. But the project has been delayed until now.

By the scheduled start date for the project, scientists had made a series of technical breakthroughs needed to develop such a huge telescope, according to Yan. Despite their readiness, it took several more years to get forestry authorities' approval to build the telescope in the area and to deal with the relocation of 12 households.

Wu Jiao contributed to this story.

China Daily

(China Daily 03/14/2011 page6)