The discovery of the "Chinese Eye of Heaven" is expected to open a new window for exploring the universe. China | Hertz | Eye of Heaven
The Chinese pulsar time array research team, which is composed of scientific researchers from the National Astronomical Observatory of the Chinese Academy of Sciences and other units, has recently used the "Chinese Celestial Eye" FAST to detect key evidence of the existence of the NaHz gravitational waves, marking that China's detection and research of the NaHz gravitational waves have reached the world's leading level synchronously, and is expected to open a new window for the use of the NaHz gravitational waves to explore the universe.
What is a nanohertz gravitational wave? How difficult is the detection? How was this discovery made? Xinhua News Agency reporters interviewed authoritative experts to interpret this.
Panoramic view of China's Heavenly Eye. Photo by Xinhua News Agency reporter Ou Dongqu
Gravitational waves are spatiotemporal ripples caused by the disturbance of surrounding spacetime by a mass object accelerating motion. Nanohertz gravitational waves are one of them, named after their frequency as low as nanohertz.
"Gravitational wave signal is extremely weak, but it is a direct means to detect the non luminous matter in the universe. Detecting gravitational waves and observing the universe with gravitational waves is a long-term goal pursued by astronomers." Li Kejia, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences/Peking University, introduced.
![The discovery of the "Chinese Eye of Heaven" is expected to open a new window for exploring the universe. China | Hertz | Eye of Heaven](https://a5qu.com/upload/images/ee35f7a75bef47973e0e27ae8f4b39cb.jpg)
In the 1970s and 1980s, the existence of gravitational waves was indirectly confirmed. In 2016, gravitational waves in the hundred hertz frequency band were detected, and these two discoveries won the Nobel Prize in Physics.
Astronomical theory suggests that larger celestial bodies generate lower frequencies of gravitational waves, and the gravitational waves generated by the rotation of the most massive celestial bodies in the universe are mainly concentrated in the nanohertz frequency band. Therefore, detecting nanohertz gravitational waves is of great significance for understanding issues such as supermassive black holes, galaxy merging history, and the formation of large-scale structures in the universe.
"Due to its extremely low frequency, period of several years, and wavelength of several light years, the detection of nanohertz gravitational waves is very challenging." Li Kejia introduced that using a large radio telescope to observe a batch of millisecond pulsars with extremely regular rotation for long-term time measurement is the only known method for detecting nanohertz gravitational waves.
Research teams from the United States, Europe, and Australia have conducted approximately 20 years of nanohertz gravitational wave searches using their respective large radio telescopes.
Panoramic view of China's Heavenly Eye. Photo by Xinhua News Agency reporter Ou Dongqu
![The discovery of the "Chinese Eye of Heaven" is expected to open a new window for exploring the universe. China | Hertz | Eye of Heaven](https://a5qu.com/upload/images/49197f9d623df06272ce1494fb91bd08.jpg)
In this study, the CPTA research team used the "Chinese Eye" to conduct long-term systematic monitoring of 57 millisecond pulsars, and analyzed data spanning 3 years and 5 months. They discovered evidence of quadrupole correlation signals with nanohertz gravitational wave characteristics, with an error rate of less than one in 500000.
"The detection sensitivity of NaHz gravitational waves strongly depends on the observation time span. The CPTA research team has made full use of the excellent performance of the 'Chinese Celestial Eye' to make China's detection and research of NaHz gravitational waves reach the world's leading level synchronously with the advantages of data accuracy, pulsar number and data processing algorithm." said Chang Jin, president of the National Astronomical Observatory of the Chinese Academy of Sciences.
"With the accumulation of the observation data of the 'Chinese Celestial Eye', our scientific research team will make more discoveries. The National Astronomical Observatory of the Chinese Academy of Sciences will further speed up the research on the detection of the NaHz gravitational waves, helping to open a new window for the exploration of the universe using the NaHz gravitational waves," said Chang Jin.
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