More than 9,000 people in southwest China will need to leave their homes in order to make space for the world's largest radio telescope.

Residents living within five kilometres of the Five-hundred-metre Aperture Spherical Telescope (FAST) being built in Guizhou province will need to relocate in order to create a "sound electromagnetic wave environment," a government official told China's state-run news agency Xinhua.

Devices such as cellphones, microwave ovens and garage door openers all generate radio waves that can be detected by a radio telescope and interfere with scientific measurements.

The telescope is expected to be completed in September.

Li Yuecheng, secretary general of the Guizhou Provincial Committee of the Chinese People's Political Consultative Conference, said relocated residents will be resettled in two nearby counties by the end of September, and each will receive 12,000 yuan ($2,556) in compensation from the government. Ethnic minority households with housing difficulties will get an extra 10,000 yuan ($2,129).

Radio telescopes are designed to detect radio waves emitted by distant astronomical objects such as galaxies, supernovas, pulsars and quasars, providing information about their masses and how far away they are. Such signals are extremely weak, so many radio telescopes are enormous.

Some radio telescopes also do radar studies — they bounce radio signals off objects such as asteroids and other planets in our solar system to detect the signal that comes back to Earth in order to generate an image.

FAST, which began construction in 2011, is managed by the National Astronomical Observatories of the Chinese Academy of Sciences in partnership with the government of Guizhou province. It's being funded by 1.2 billion yuan ($260 million) from China's National Development and Reform Commission.

According to the official FAST website, the new telescope is similar to the Arecibo radio observatory in Puerto Rico, currently the world's largest single-dish radio telescope at 305 metres in diameter.

Unique landscape required

Such enormous, immovable single-dish radio telescopes need to be built in rare and unique landscape forms that are already large and dish-shaped, says Mark Halpern, a radio astronomer and astronomy professor at the University of British Columbia. That's why the telescope is being built in an area where people are now living rather than a remote region.

In Canada, the much smaller and pointable Dominion Observatory in Penticton, B.C., which is just 26 metres in diameter, is surrounded by hills, and located in a nature preserve, far from people's homes.

"We can see a single cellphone on Mars, so a cellphone nearby is a bad thing," Halpern said.

Signs on the nearest highway to the observatory warn people they're in an electromagnetic protected zone and can't use a cellphone, he added. The nearest houses can't have microwave ovens or garage door openers.

Such rules would be hard to enforce if too many people live near the telescope, Halpern said, which is likely why China wants to move them.

The Algonquin Radio Observatory, a 46-metre dish telescope in Pembroke, Ont., which is operated privately by Thoth Technology Inc., is 50 kilometres from the nearest building, says Brendan Quine, chief technical officer for the company and an engineering professor at York University.

The facility bans cellphones, has no Wi-Fi, and keeps cars at a distance, as their sparkplugs could potentially produce signals that interfere with measurements of objects such as pulsars. Those are neutron stars that give off regular pulses of radio waves.

"We're looking at objects which might be right at the edge of the universe," Quine said. "Any local sources which are broadcasting at similar frequencies would just totally swamp that type of measure... So I understand why the Chinese are planning to move people five kilometres away from their antennas."

Corrections

  • An earlier version of this story stated that the Dominion Observatory was the largest dish-shaped radio telescope in Canada. In fact, the Algonquin Radio Observatory is larger.
    Feb 16, 2016 3:57 PM ET