Five-hundred-meter Aperture Spherical Telescope

In the karst hills of Pingtang County in Guizhou, southern China, a natural bowl-shaped depression called Dawodang has been lined with the largest single-dish radio telescope ever built. The Five-hundred-meter Aperture Spherical Telescope — FAST, known in China as Tianyan, the "Sky Eye" — is a reflector 500 metres across, made from some 4,450 triangular panels. Rather than tilting, the dish changes shape: thousands of actuators pull the cable net beneath the panels so that, at any moment, an area about 300 metres wide becomes a parabola aimed at the target, while the receiver cabin hangs above on cables and moves to the focus.

FAST is operated by the National Astronomical Observatories of the Chinese Academy of Sciences. The idea was championed for more than two decades by the astronomer Nan Rendong, who searched southern China for a suitable limestone sinkhole and led the project until his death in 2017. Construction was completed and the telescope began commissioning on 25 September 2016; formal operations started in January 2020 after years of testing.

Its sensitivity has made it the world's most prolific pulsar finder. The first two new pulsars were announced in 2017, the tally passed 1,000 in 2024, and by October 2025 it stood at more than 1,150 — more than all other telescopes found over the same period. FAST also studies fast radio bursts, neutral hydrogen in galaxies and interstellar molecules, and takes part in efforts to detect gravitational waves through pulsar timing.

Getting there

The telescope lies in the countryside about 71 km from Dushan; the nearest airport given is Guiyang Longdongbao International (KWE), roughly 99 km away as the crow flies, and the drive through the mountains is considerably longer. A tourist area has been developed in nearby Kedu, with an astronomy museum and visitor facilities. The telescope sits at the centre of a 5-km radio-silent zone: visitors must deposit mobile phones, cameras, smart watches and other electronics at the visitor centre before the shuttle bus takes them to the viewing platform above the dish.