The supermassive black hole residing at the core of the M87 galaxy, renowned for the groundbreaking image capturing its shadow, has unveiled yet another milestone: the confirmation of a wobbling jet emanating from the black hole, offering conclusive evidence of its rotational motion.
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. 2023, Intouchable Lab@Openverse and Zhejiang Lab
Supermassive black holes, colossal entities weighing billions of times more than the Sun and voraciously consuming all matter, including light, pose a formidable challenge for scientific investigation.
Their impenetrable nature means that only a handful of their properties can be theoretically probed. One such property that holds the potential for observation is their spin, but the formidable complexities involved have thus far hindered any direct assessment of black hole spin.
In pursuit of evidence regarding black hole spin, an international research team meticulously analyzed more than two decades’ worth of observational data pertaining to the galaxy M87. Situated 55 million light-years distant within the Virgo constellation, this galaxy shelters a black hole with a staggering mass 6.5 billion times that of the Sun.
This very same black hole was responsible for delivering the inaugural image of a black hole's shadow through the Event Horizon Telescope (EHT) in 2019.
The supermassive black hole within M87 boasts both an accretion disk, responsible for funneling matter into the black hole, and a jet, from which matter is expelled at nearly the speed of light.
To investigate this phenomenon, the research team meticulously scrutinized data from 170 distinct time frames gathered by an extensive network of observatories, including the East Asian VLBI Network (EAVN), the Very Long Baseline Array (VLBA), the collaborative array of KVN and VERA (KaVA), and the sprawling East Asia to Italy Nearly Global (EATING) VLBI network. Over 20 radio telescopes worldwide contributed to this comprehensive study.
The findings unveiled that gravitational interactions between the accretion disk and the black hole's spin induce a distinctive wobbling akin to the precession seen in Earth's motion due to gravitational interactions within the Solar System. This observation conclusively links the jet’s dynamics with the central supermassive black hole, offering direct proof of the black hole’s rotational motion.
The jet undergoes a directional shift of approximately 10º, exhibiting a precession cycle lasting 11 years, a congruence with the outcomes of theoretical supercomputer simulations conducted by ATERUI II at the National Astronomical Observatory of Japan (NAOJ).
We are thrilled by this significant finding. 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 M87 structure over two decades and thorough analysis are essential to obtain this achievement.
Yuzhu Cui, Study Lead Author, National Astronomical Observatory of Japan
The jet undergoes a directional shift of approximately 10º, exhibiting a precession cycle lasting 11 years, a congruence with the outcomes of theoretical supercomputer simulations conducted by ATERUI II at the National Astronomical Observatory of Japan (NAOJ).
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. Now anticipation has turned into certainty. This monster black hole is indeed spinning.
Dr Kazuhiro Hada, National Astronomical Observatory of Japan
“This is an exciting scientific milestone that was finally revealed through years of joint observations by the international researchers team from 45 institutions around the world, working together as one. Our observational data beautifully fitted to the simple sinusoidal curve bring us new advances in our understanding of black hole and jet system,” stated Dr Motoki Kino at Kogakuin University, the coordinator of the East Asian VLBI Network Active Galactic Nuclei Science Working Group.
Journal Reference:
Cui, Y., et al. (2023). Precessing jet nozzle connecting to a spinning black hole in M87. Nature. doi.org/10.1038/s41586-023-06479-6.