Led by Chinese scientists, Einstein's predictions were confirmed!

The black hole that humans "saw" for the first time was proven to be spinning!

Thanks to the joint efforts of an international scientific research team led by Chinese scientists and consisting of 45 scientific research institutions around the world, the black hole M87, which was "seen" by humans for the first time, was proven to be spinning, a phenomenon that is consistent with the relevant predictions of Einstein's general theory of relativity .

On September 27, the relevant research results were published in the international academic journal Nature.

Schematic diagram of the tilted accretion disk model.

The black hole that humans "saw" for the first time is located at the center of a giant elliptical galaxy M87 in Virgo, 55 million light-years away from Earth, and has a mass of about 6.5 billion times that of the sun. In 2019, scientists released the first image of the M87 black hole, and have continued to conduct observational studies on the M87 black hole since then.

Cui Yuzhu, the first author and corresponding author of the paper on this latest research result and a postdoctoral fellow at Zhijiang Laboratory, said that using the very long baseline interferometry (VLBI) technology, researchers were surprised to find that the direction of the M87 black hole jet observed by the East Asian VLBI network in March 2017 was different from before. Focusing on this clue, through in-depth analysis of observation data from multiple VLBI networks around the world in the past 23 years, it was finally found that the M87 black hole jet showed periodic oscillations, with a oscillation period of about 11 years and an amplitude of about 10 degrees. This provided the most powerful observational evidence for the black hole spin theory for the first time.

Supermassive black holes at the center of active galaxies are one of the most destructive and mysterious celestial bodies in the universe. They have a huge gravitational force, "eating" a large amount of matter through accretion disks, and "spitting" matter out at a high speed close to the speed of light, with such a great force that they can "spit" thousands of light years away. What force in the universe can change the direction of a black hole's jet and cause it to oscillate periodically?

Top: The jet structure of M87 after the merger every two years between 2013 and 2018, observed at 43 GHz. Bottom: The best fit based on images of the mergers in one year from 2000 to 2022.

In a more in-depth study, the research team conducted a lot of theoretical research and detailed analysis based on the observation results, and used supercomputers combined with the latest data to perform numerical simulations. The results confirmed that when there is an angle between the rotation axis of the accretion disk and the spin axis of the black hole, the reference frame "dragging effect" will cause the entire accretion disk to swing, and the jet will also swing due to the influence of the accretion disk. This phenomenon is consistent with Einstein's general relativity prediction that "if the black hole is in a rotating state, it will cause a reference frame dragging effect."

Lin Weikang, an associate researcher at the Southwest Institute of Astronomy of Yunnan University, said that although spin is a basic assumption of black hole theory, it has not been directly confirmed by observation before. This study successfully linked the dynamics of the M87 black hole jet to the state of the supermassive black hole at the center of the galaxy, supporting the basic theory while providing key elements for further unveiling the mystery of black holes.

Very long baseline interferometry (VLBI) technology can combine multiple radio telescopes located in different locations around the world to achieve the observation effect of a very large telescope. In this latest study, data from multiple international observation networks including the East Asian VLBI Network were used. A total of more than 20 radio telescopes around the world contributed to this study, including the 65-meter Tianma Telescope at the Shanghai Astronomical Observatory of the Chinese Academy of Sciences and the 26-meter Nanshan Radio Telescope at the Xinjiang Astronomical Observatory.

Since 2017, these two radio telescopes in my country have been continuously participating in the East Asian VLBI network observations, playing an important role in improving the observation sensitivity and angular resolution. According to Shen Zhiqiang, director of the Shanghai Astronomical Observatory of the Chinese Academy of Sciences, the observatory has recently started construction of a 40-meter radio telescope in Shigatse, Tibet, which will further enhance the high-resolution millimeter-wave imaging observation capabilities of the East Asian VLBI network after completion.

Li Qi, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, chief scientist of the "China Sky Eye", and chief scientist of computational astronomy at the Zhijiang Laboratory, believes that this research achievement led by Chinese scientists is inseparable from the deep integration of radio astronomy and computational science . As data continues to accumulate, the Zhijiang Laboratory is introducing technologies such as artificial intelligence and cloud computing into the field of astronomy, and multiple disciplines are working together to explore the mysteries of the universe.

Planning and production

Source: Xinhua News Agency

Reporter: Zhang Jiansong, Dong Xue

Editor: Cui Yinghao