FAST marks decade of discoveries

Chinese astronomers have hailed the achievements made by China's Five-hundred-meter Aperture Spherical radio Telescope, or FAST, highlighting the global recognition amassed and future breakthroughs that will follow upgrades to the telescope.

"Sensitivity is a core indicator of observational capability for radio waves. As the world's most sensitive single-dish radio telescope, FAST has an irreplaceable advantage in the field, providing a unique 'probe' for humanity to explore the universe," said Jiang Peng, chief engineer of FAST and deputy director of the National Astronomical Observatories of the Chinese Academy of Sciences.

Jiang highlighted how FAST's performance had significantly exceeded initial expectations, noting that "all technical indicators have been met, and its operational efficiency and reliability are exceptional". Jiang made the remarks on Wednesday during a three-day academic exchange event held in Pingtang county, Guizhou province, to mark the 10th anniversary of the completion of FAST. The event attracted over 200 Chinese scholars from more than 40 research institutes and universities.

Over the past decade, FAST has discovered over 1,300 pulsars, surpassing the total found by all other radio telescopes worldwide during the same period. It has also captured 156,000 neutral hydrogen galaxies, establishing the world's largest sample library to trace the birth and evolution of galaxies.

Notably, FAST has discovered many exotic pulsars, Jiang said, including a pulsar binary with the shortest known orbital period and a pulsar-helium-star system that provides strong observational evidence for common-envelope evolution — a dramatic stellar phase in which one star engulfs its companion, ejects their shared outer layers, and leaves behind a tightly bound compact binary.

"When FAST began full operations in 2020, the number of observation proposals was modest. Now, demand has surged, with an annual approval rate of only 15 percent, demonstrating global recognition and our commitment to open and shared science," Jiang said.

He emphasized that behind these achievements was a dedicated team of over 100 researchers and engineers, staying true to the vision of the late Nan Rendong — who had worked as the chief scientist on the project — to building a world-class telescope for the nation. The team has overcome pressures from construction, testing, and operation, tackling challenges such as the domestic development of high-performance steel cables and actuators, as well as the precision refinement of the measurement and control system.

The team is now actively advancing Phase II of the project, with plans to deploy dozens of 40-meter-diameter antennas within a 30-kilometer radius of FAST. Once completed, this expansion is expected to double FAST's sensitivity and boost its resolution by 200 times.

Earlier this year, an international research team led by Wu Xuefeng, a researcher at the CAS' Purple Mountain Observatory in Nanjing, Jiangsu province, published a breakthrough in the journal Science based on FAST, providing strong evidence that at least some fast radio bursts — mysterious flashes of radio energy from deep space — are produced by compact star binaries.

Like super lightning of the universe, fast radio bursts are extremely bright and transient radio phenomena, lasting only a few thousandths of a second. Wu attributed the groundbreaking discovery to the superior performance of FAST, along with its long-term monitoring and rapid response mechanisms that kick in once important abnormalities are found.

"With the advancement of Phase II of the FAST project, further improvements in sensitivity will enable astronomers to contribute significantly to uncovering the ultimate question of the origin of fast radio bursts," he said, noting that the telescope has provided a platform for global leading scientists to collaborate and pursue breakthroughs in both theoretical and observational astronomy.

Han Zhanwen, a CAS member and a researcher at the CAS' Yunnan Observatories in Kunming, echoed Wu's views, underscoring that FAST's ultrahigh sensitivity has opened a new window for scientists, enabling the observation of many faint neutron stars and pulsars that were previously undetectable.

Han emphasized that the most significant improvement in Phase II of the project is resolution. He compared the project's first phase to hearing someone speaking in a room without being able to identify the speaker, whereas Phase II of the project can precisely locate the source of the sound.

"This will greatly enhance the capability for multiband joint observations, allowing us to accurately identify the optical and X-ray counterparts of radio sources, thereby revealing deeper physical laws," he added.

limenghan@chinadaily.com.cn