Aerial photo taken on June 23 shows the Five-hundred-meter Aperture Spherical Radio Telescope (FAST)  in Guizhou. (PHOTO: XINHUA)

Edited by LIANG Yilian

Key evidence of the existence of nanohertz gravitational waves based on pulsar timing observations was found through the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) or the "China Sky Eye."

The research was conducted by the Chinese Pulsar Timing Array (CPTA), which comprises researchers from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) and other institutions. The findings were published online in the Chinese journal Research in Astronomy and Astrophysics on June 29.

The study of nanohertz gravitational waves is one of the current focuses in the field of physics and astronomy. However, the waves are incredibly challenging to detect because of their extremely low frequency, and wavelengths that run into light years, and periods that can cover several years. The only known way to detect them is using large radio telescopes to conduct long-term observation.

Bolstered by high sensitivity, the CPTA research team monitored 57 millisecond pulsars with regular cadence for 41 months. They found key evidence for quadrupole correlation signatures compatible with the prediction of nanohertz gravitational waves at a 4.6-sigma statistical confidence level, Li Kejia, the corresponding author of the paper and professor at NAOC, told the Global Times. The false alarm probability is two in one million.

But due to the short observation time, the researchers have not yet been able to determine the main physical source of the waves.

Other international researchers have also announced similar results around the same time, including those from the North American Nanohertz Observatory for Gravitational Waves and the Australian Parkes Pulsar Timing Array.

"Four international teams independently obtained key evidence for the existence of nanohertz gravitational waves, which allowed the results to corroborate each other, further improving the accuracy of this result," Li told Science and Technology Daily.