Aerial photo taken on the early morning of July 25, 2022 shows a panoramic view of China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST) under maintenance in Southwest China's Guizhou Province. Photo: Xinhua

Chinese and US astronomers have recently filmed for the first time the magnetic field changes in the surrounding environment just one astronomical unit away from the center of the fast radio burst (FRB) located outside the Milky Way using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST).

The observation is an important step toward revealing the engine mechanism of the FRB center, China's state media Xinhua News Agency reported on Thursday.

Led by specialists from the National Astronomical Observatories under the Chinese Academy of Sciences (CAS), the international group reported the detection of 1,863 bursts in 82 hours over 54 days from the repeating source FRB 20201124A.

FRBs are the brightest, most highly dispersed millisecond-duration astronomical transients in radio bands. Their origins still remain unknown. The astronomers' latest observations revealed a complicated, dynamically evolving, magnetized immediate environment within about an astronomical unit (or distance between the Earth and the Sun) of the radio source, according to the study published in the journal Nature on Wednesday.

The scientists found for the first time that the Faraday rotation measure, an indicator for magnetic field strength, jolted irregularly in the first 36 days, followed by an 18-day period of stability. The findings showed that the vibrant, fast radio burst had eased within 72 hours, a phenomenon previously undetected, according to Xinhua.

"These findings suggest that the environment around 1 astronomical unit of the fast radio burst FRB 20201124A is very complex and evolving dynamically," said Li Kejia, a researcher of the group at Peking University/National Astronomical Observatory.

Li said the team is conducting further research and expects to find direct observational evidence that determines the physical processes and energy mechanisms at the core of fast radio bursts, and to reveal the physical origin of the mysterious cosmic phenomenon of fast radio bursts.

FAST, also known as the "China Sky Eye," is located in a naturally deep and round karst depression in Southwest China's Guizhou Province. FAST started formal operation in January 2020 and officially opened to the world on March 31, 2021. It is believed to be the world's most sensitive radio telescope.

In June 2022, a research team discovered and located the first persistently active repeating FRB with the help of FAST.