FAST radio telescope

China's Five-hundred-metre Aperture Spherical Telescope sits in a natural valley in Guizhou province. It began observations in 2016 and has since found hundreds of new pulsars.

It is the largest single-dish instrument. Arrays of many dishes can be larger when combined.

Context

FAST, nicknamed the Chinese Sky Eye, was built in a natural karst depression, a bowl-shaped valley formed in limestone, which saved on excavation costs. Its reflector is made of about 4,400 triangular panels that can be shifted by cables and actuators to change shape and point at different parts of the sky.

Although the dish is 500 metres across, only an area roughly 300 metres wide is used for any single observation at a time. It saw first light in September 2016 and began regular science operations a few years later, after commissioning work.

FAST is the largest single-aperture radio telescope in the world. It took that title from the 305-metre Arecibo Observatory dish in Puerto Rico, which collapsed in December 2020 after cable failures. Larger arrays exist, but they link many separate antennas instead of using one dish.

It is especially good at finding pulsars, which are fast-spinning neutron stars that emit beams of radio waves, and has found hundreds of new ones. It also searches for neutral hydrogen gas in distant galaxies and listens for possible signals from other civilisations.