The World’s Largest Radio Telescope Is Now Live

China’s FAST telescope dwarfs Arecibo and went live on Sunday afternoon.

Daniel Oberhaus

Daniel Oberhaus

Image: CCTV News/YouTube.

So far 2016 has been a year of unprecedented achievement for China's ambitious space program: the country has launched a dark-matter seeking satellite, put another satellite to test quantum communications in orbit, outlined plans to send rovers to Mars and the dark side of the moon, and successfully launched a new Long March rocket. This new Long March rocket will soon be ferrying Chinese astronauts (aka taikonauts) to Tiangong-2, China's second crewed space station which was just put into orbit earlier this month.

Although China's space program has accomplished more in the last nine months than many space agencies do in several years, the country's progress is still not showing any signs of flagging. In July, Chinese engineers finished construction on the Five-hundred-meter Aperture Spherical Telescope (FAST), the world's largest radio telescope. On Sunday afternoon, FAST came online for the first time and ushered in an exciting new era for Chinese astronomy.

"The ultimate goal of FAST is to discover the laws of the development of the universe," said Qian Lei, an associate researcher with the National Astronomical Observatories of the Chinese Academy of Sciences.

Construction on the FAST telescope (nicknamed Tianyan, or 'Eye of Heaven') began about five years ago in southwestern China. A natural basin in the area proved to be a perfect spot to put the massive dish, but the construction project will displace about 9000 people from their homes to reduce radio interference. Originally projected to cost around $100 million, by the time everything was said and done China had dumped some $180 million into the project.

At 500 meters in diameter, the FAST radio telescope is about 200 meters larger than the Arecibo telescope in Puerto Rico, which came online in 1963. Like Arecibo, the FAST telescope is a fixed dish telescope which means it can't be moved and must observe the sky that is directly overhead—but that doesn't mean it can't be focused to look at different sections of that patch of sky.

FAST achieves this by having an adjustable detector suspended over the dish which can be manipulated with pulleys and objects moving across the sky can be tracked by adjusting the angles of the 4,450 panels that comprise the dish. Compared to Arecibo, this state-of-the-art radio telescope will be able to observe almost three times as much sky area, at twice the sensitivity and up to ten times the surveying speed.

For astronomers, the completion of FAST couldn't come fast enough. Arecibo has been plagued by funding woes for years and today its future is entirely uncertain. Losing Arecibo would be a major blow to astronomy and SETI research, and although the FAST telescope could pick up some of the slack if Arecibo is decommissioned in the future, the two telescopes aren't trying to do the same thing.

Fast telescope under construction. Image: Wikimedia Commons.

Unlike Arecibo, which is used for everything from listening for extraterrestrial transmissions to hunting for giant killer asteroids and studying Earth's atmosphere, FAST will primarily be investigating the evolution of the universe as it is written in neutral hydrogen, the raw material of stars and the most abundant element in the universe. It will also be on the lookout for pulsars, the rotating remnants of dead stars which could reveal gravitational waves emitted from black holes. And yes, in the process it might even pick up a call from ET.

"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 is approaching us," said Qian.

Initial FAST tests have been encouraging: a recent test detected a pulsar that was 1,351 light-years away. Yet FAST is still not running anywhere close to its full capacity, and when it will be able to do so in uncertain. A report from Caixin, a Beijing news agency says getting the telescope fully operational will require dozens, if not hundreds of astronomers, but so far the country hasn't even been able to track down 50 people for the job.