An international research team led by Chinese scientists has unveiled a recurring cycle in the precessing motion of an oscillating jet of a supermassive black hole at the heart of the distant galaxy M87, providing compelling observation evidence for the black hole spin.

The new finding, published in the journal Nature on Wednesday, helps prove that the black hole inside M87 is actually spinning.

The researchers found the jet expelled from the black hole swinging up and down with an amplitude of about 10 degrees, suggesting a recurring 11-year cycle.

The research is based on extensive analysis of data recorded from 2000 to 2022 by various international networks of radio telescopes, said Cui Yuzhu, the first author and corresponding author of the paper.

The black hole of the M87 galaxy sits about 55 million light-years from Earth, with a mass 6.5 billion times that of the sun. In 2019, scientists captured the first-ever image of such a black hole, offering the first direct visual evidence of an unseeable cosmic object and its shadow. Since then, the researchers have been observing and studying the black hole.

Such a supermassive black hole at the center of an active galaxy is among the most enigmatic and formidable entities in the universe. Its immense gravitational pull enables it to "gobble up" a large amount of matter through the accretion disk while "spitting out" matter close to the speed of light to thousands of light years away.

The research team also combined their observation data with theoretical simulations using a supercomputer. They proved that the rotation axis of the accretion disk misaligns with the black hole's spin axis, leading to the precessing jet, as predicted by Einstein's theory of general relativity. Over 20 telescopes globally also contributed to their study in the period.

The black hole spin represents a fundamental hypothesis in black hole theories. However, there was no previous direct observation evidence. The new discovery can provide a pivotal element for further unraveling the mystery of black holes, said Lin Weikang, associate research professor from the South-Western Institute for Astronomy Research of Yunnan University.