China tests world’s largest radio telescope: What's it hunting for?

The search is on in China to better understand the cosmos, its origins, and, perhaps, find extraterrestrial life.

China has started to test its Five-hundred-meter Aperture Spherical Telescope (FAST), unveiling the world’s largest radio telescope at a ceremony Sunday. While Chinese scientists will spend the next three years testing, tuning, and calibrating the dish, it has already made one discovery. It has detected radio signals from a pulsar about 1,351-light-years away, one of thousands of remnants of burned-out stars the telescope is expected to discover in its lifetime, according to Qian Lei, an associate researcher with the National Astronomical Observation under the Chinese Academy of Sciences.

The telescope – which spans 1,640-feet, and whose combined area is equal to almost 450 basketball courts – shows China’s growing ambition to be a science and space superpower. But the country has also emphasized the importance of collaborating with the international scientific community in its quest to understand the stars and, perhaps, discover other galactic inhabitants.

"The ultimate goal of FAST is to discover the laws of the development of the universe," Dr. Qian told CCTV, the Chinese state broadcaster. "In theory, if there is civilization in outer space, the radio signal it sends will be similar to the signal we can receive when a pulsar (spinning neutron star) is approaching us."

The telescope, comprised of 4,450 panels, is nestled in a natural crater in the remote Pingtang county in China's southern Guizhou province. Green hillsides of karst formations, dissolved and eroded over eons, envelope the wok-shaped dish. It is the ideal environment for a radio telescope, according to The New York Times. The karst serve as a natural barrier against earthly radio noise and wind that could drown out whispers from space. The second largest radio telescope, the Arecibo Observatory in Puerto Rico, was built into a similar environment.

About 984 feet, or 300 meters, wide, the Arecibo Observatory was used by Joseph Taylor, an astronomer at Princeton University, in his discovery of indirect proof of gravitational waves, which earned him a Nobel Prize in 1993.

FAST has double the sensitivity of its Puerto Rican counterpart, and five to 10 times the surveying speed, according to Xinhua.

Yet, both telescopes more or less operate the same way: They detect electromagnetic radiation in the cosmos.

“This is light with a wavelength a million times or so longer than our eyes can detect,” writes Elias Brinks, an astronomer at the University of Hertfordshire, in a contribution to US News and World Report. “Not surprisingly, the sky at these long wavelengths looks vastly different, which is exactly why observations at radio wavelengths reveal information that is not accessible with optical telescopes.”

The resolution of the images will appear much worse than how we see the world with our own eyes. But the sheer size of FAST will allow it to collect vast amounts of signals from even the deepest reaches of space.

"A radio telescope is like a sensitive ear, listening to tell meaningful radio messages from white noise in the universe.” Nan Rendong, chief scientist of the FAST project with the National Astronomical Observatories, Chinese Academy of Sciences, told Xinhua when the construction of FAST was completed in July. “It is like identifying the sound of cicadas in a thunderstorm."

FAST is optimized to detect neutral hydrogen, “the most abundant element in the universe, and raw materials from which stars are formed,” writes Dr. Brinks.

“FAST will be able to make a complete census down to much lower levels of the hydrogen content of the local universe than has been possible so far,” he says. “How much hydrogen is found, where and in what kind of agglomerations, will have direct consequences for how scientists think the universe evolved from its earliest phase and how galaxies formed and have continued to grow with time.”

The telescope is also expected to discover thousands of pulsars, according to Xinhua. Pulsars can serve as “high-precision clocks” to reveal gravitational waves from black holes or even the Big Bang, offering a window into the beginnings of the universe.

China also hopes to use the telescope to search for signs of alien life. The telescope could detect extraterrestrial signals sent to Earth, intentionally or accidentally. This search has proven fruitless in the six decades the world has sought out extraterrestrial life. But FAST marks a significant investment in this search. The $180-million price of the project (which some have reported sounds modest) is much more than the "shoestring" this quest has operated on, as Pete Spotts reported for The Christian Science Monitor in July 2015.  

The results of that search aren't expected to come soon, as scientists must calibrate the telescope over the next three years. But, FAST also represents a shift in the types of investments China has made. 

“Chinese science is often seen as serving the country’s economic and military expansion, seeking ruthlessly practical dividends,” wrote Chris Buckley and Adam Wu for The New York Times. “But the telescope shows the government in Beijing is also willing to spend heavily to propel China high into the big leagues in research that offers few direct payoffs, apart from knowledge and prestige.”

This report contains material from the Associated Press.