Messier 87 is a giant elliptical galaxy located some 53 million light-years away in the constellation of Virgo. In April 2019, astronomers from the Event Horizon Telescope (EHT) Collaboration released stunning images of M87*, the supermassive black hole in the center of Messier 87. M87* is known to have an accretion disk, which feeds matter into the black hole, and a relativistic jet. Now, M87* has yielded another first: the jet shooting out from the black hole has been confirmed to wobble, providing direct proof that M87* is spinning.
Schematic representation of the tilted accretion disk model. The black hole spin axis is assumed to be straight up and down in this illustration. The jet direction points almost perpendicular to the disk plane. The misalignment between the black hole spin axis and disk rotation axis triggers the precession of the disk and jet. Image credit: Cui et al. / Intouchable Lab@Openverse / Zhejiang Lab.
“Supermassive black holes, monsters up to billions of times heavier than the Sun that eat everything around them including light, are difficult to study because no information can escape from within,” said Dr. Yuzhu Cui, an astronomer at the Zhejiang Laboratory and the National Astronomical Observatory of Japan (NAOJ), and colleagues.
“Theoretically, there are very few properties that we can even hope to measure.”
“One property that might possibly be observed is spin, but due to the difficulties involved there have been no direct observations of black hole spin.”
In the study, the astronomers accurately traced the long-term evolution of the jet near M87*.
They analyzed 170 very long baseline interferometry images of the jet obtained with the East Asian VLBI Network (EAVN) and the Very Long Baseline Array (VLBA) between 2000 and 2022.
Their results show that gravitational interactions between the accretion disk and the black hole’s spin cause the base of the jet to wobble, or precess, much the same way that gravitational interactions within the Solar System cause the Earth to precess.
The authors successfully linked the dynamics of the jet with the central supermassive black hole, providing direct evidence that the black hole does in fact spin.
The jet’s direction changes by about 10 degrees with a precession period of 11 years, matching theoretical supercomputer simulations.
“We are thrilled by this significant finding,” Dr. Cui said.
“Since the misalignment between the black hole and the disk is relatively small and the precession period is around 11 years, accumulating high-resolution data tracing the structure over two decades and thorough analysis were essential to obtain this achievement.”
“After the success of black hole imaging in this galaxy with the EHT, whether this black hole is spinning or not has been a central concern among scientists,” said Dr. Kazuhiro Hada, an astronomer at NAOJ.
“Now anticipation has turned into certainty. This monster black hole is indeed spinning.”
“Our observational data beautifully fitted to the simple sinusoidal curve bring us new advances in our understanding of black hole and jet system,” said Dr. Motoki Kino, an astronomer at Kogakuin University.
The study appears today in the journal Nature.
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Y. Cui et al. 2023. Precessing jet nozzle connecting to a spinning black hole in M87. Nature 621, 711-715; doi: 10.1038/s41586-023-06479-6
