China’s 500-metre “Sky Eye,” the world’s largest single-dish radio telescope cradled in a mountain bowl, has now found over 1,000 pulsars: More than all foreign telescopes combined during the same period

The telescope as seen from above in 2025 | Wikimedia CommonsTucked into a vast natural depression in the mountains of Pingtang County, Guizhou Province, China’s Five-hundred-meter Aperture Spherical Radio Telescope (FAST) has quietly become the world’s most productive pulsar hunter. Better known as the “Sky Eye,” the 500-metre-wide observatory has now discovered more than 1,000 pulsars, crossing a milestone unmatched by any other single radio telescope. According to the State Council of the People’s Republic of China, FAST has identified over 1,000 new pulsars, a total that exceeds the combined number discovered by all foreign telescopes during the same period. Scientists say the achievement reflects the telescope’s exceptional sensitivity and marks a major advance in radio astronomy. The telescope as seen from above in 2025 | Wikimedia CommonsBuilt inside a mountain to listen to the faintest signals in spaceFAST was designed to detect radio waves so weak that they would be lost amid interference almost anywhere else. Engineers constructed the telescope inside a naturally occurring karst sinkhole, using the surrounding mountains as a shield against human-generated radio noise. The enormous dish measures 500 metres (1,640 feet) in diameter, making it the world’s largest filled-aperture single-dish radio telescope. According to the Chinese Academy of Sciences, FAST was completed in 2016, entered formal operation in 2020 and opened to international scientists in 2021, providing researchers with one of the most sensitive instruments ever built for studying pulsars, neutral hydrogen and fast radio bursts. More than 1,000 pulsars are giving astronomers new tools to study the universePulsars are the dense remnants left behind when massive stars explode as supernovae. Although only about 20 kilometres across, they can contain more mass than the Sun and rotate hundreds of times each second, emitting narrow beams of radio waves that sweep across Earth with extraordinary regularity. According to Han Jinlin, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, each pulsar has a unique rotational pattern, allowing astronomers to use them as highly precise natural clocks. Han said the expanding catalogue of pulsars is helping scientists investigate stellar evolution, test theories of gravity and improve understanding of the Milky Way, while future deep-space missions may eventually use pulsars as natural navigation beacons. One survey alone has transformed the search for neutron starsMuch of FAST’s success comes from dedicated sky surveys that repeatedly scan the Milky Way with unprecedented sensitivity. One of the most productive surveys, the FAST Galactic Plane Pulsar Snapshot (GPPS) Survey, recently reported the discovery of 473 previously unknown pulsars, bringing the survey’s total to 751 new pulsars. According to the GPPS research team, the discoveries include numerous millisecond pulsars, binary pulsars, rotating radio transients and other rare neutron star systems that broaden astronomers’ understanding of how these extreme objects form and evolve. The growing sample also provides valuable targets for pulsar timing experiments that aim to detect low-frequency gravitational waves and study matter under conditions impossible to recreate on Earth. One of six support towers for the feed cabin | Wikimedia CommonsThe Sky Eye is becoming one of astronomy’s most valuable observatoriesAlthough pulsar discoveries have brought FAST worldwide attention, the telescope’s scientific programme extends much further. Researchers also use it to investigate fast radio bursts, map hydrogen gas throughout the Milky Way, and observe distant galaxies. International astronomers now compete for observing time because of the telescope’s unmatched sensitivity to faint radio signals. Each new pulsar strengthens one of the largest and fastest-growing catalogues ever assembled, ensuring that the giant dish hidden among the mountains of Guizhou will remain central to radio astronomy for years to come. Because FAST can detect radio signalsabout a magnitude weaker than previous radio telescope surveys, astronomers expect it to continue finding previously undetected pulsars as the GPPS survey expands across the Galactic plane.