"China's Sky Eye" has made another important new discovery!

The search for nanohertz gravitational waves is one of the hot issues in the international physics and astronomy fields. A Chinese research team recently used the "China Sky Eye" FAST to detect key evidence of the existence of nanohertz gravitational waves, which is an important breakthrough in the search for nanohertz gravitational waves.

The research was completed by the China Pulsar Timing Array (CPTA) research team composed of researchers from the National Astronomical Observatory of the Chinese Academy of Sciences and other institutions. The relevant results were published online in the academic journal Astronomy and Astrophysics Research on June 29.

Gravitational waves are ripples in spacetime caused by accelerated massive objects in the universe disturbing the surrounding spacetime. Gravitational wave signals are extremely weak, but they are a direct means of detecting non-luminous matter in the universe. Since gravitational waves produced by more massive celestial bodies have lower frequencies, detecting gravitational waves with frequencies as low as nanohertz (10 to the negative 9th power of Hertz) is of great significance for understanding supermassive black holes, the history of galaxy mergers, and the formation of large-scale structures in the universe.

A bird's-eye view of the "China Sky Eye" (taken during maintenance). Photo by Xinhua News Agency reporter Ou Dongqu

Li Kejia, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences and Peking University, said that the detection of nanohertz gravitational waves is very challenging due to their extremely low frequency, long periods of several years, and wavelengths of several light years. The only known means of detecting nanohertz gravitational waves is to use large radio telescopes to conduct long-term timing observations of a group of extremely regularly rotating millisecond pulsars.

In this study, the CPTA research team used the "China Sky Eye" to conduct long-term systematic monitoring of 57 millisecond pulsars. Based on independently developed software, they analyzed and studied data spanning 3 years and 5 months, and found evidence of quadrupole-related signals with nanohertz gravitational wave characteristics at a 4.6 sigma confidence level (false alarm rate of less than one in five hundred thousand).

Panoramic view of the "China Sky Eye" (taken during maintenance). Photo by Xinhua News Agency reporter Ou Dongqu

"The sensitivity of nanohertz gravitational wave detection strongly depends on the time span of observation. Scientific research teams in the United States, Europe and Australia have been conducting nanohertz gravitational wave searches for about 20 years respectively. The CPTA research team has made full use of the excellent performance of the 'China Sky Eye' and its advantages in data accuracy, number of pulsars and data processing algorithms to enable our country's nanohertz gravitational wave detection and research to reach the world's leading level simultaneously." said Academician Chang Jin, Director of the National Astronomical Observatory of the Chinese Academy of Sciences.

It is reported that the National Astronomical Observatory of the Chinese Academy of Sciences will further accelerate the scientific research on nanohertz gravitational wave detection, accumulate longer-term observation data, and help open a new window for using nanohertz gravitational waves to detect the universe. (Reporter Zhang Quan, Ou Dongqu)