First direct proof that monster black hole is spinning

A recent study led by Dr. CUI Yuzhu has confirmed that a supermassive black hole is spinning in the center of the nearby radio galaxy M87. 

The study, which is published in the journal Nature, was conducted by an international team of scientists using an array of radio telescopes from around the globe.

M87’s oscillating jet

Situated 55 million light-years away from Earth, M87 harbors a colossal black hole that is approximately 6.5 billion times the Sun’s mass. 

The galaxy exhibits a fascinating oscillating jet, moving up and down at an amplitude of around 10 degrees.

Two decades of data

The team meticulously analyzed telescope data spanning from 2000 to 2022, revealing a recurrent 11-year cycle in the jet base’s precessional motion. 

This discovery is consistent with predictions made by Einstein’s General Theory of Relativity, linking the jet’s dynamic behavior directly to the central supermassive black hole’s spin.

Amazing discovery 

The analysis indicates that the rotational axis of the accretion disk misaligns with the black hole’s spin axis, leading to the precessional jet. This precession provides clear evidence that the supermassive black hole in M87 is, in fact, spinning.

“We are thrilled by this significant finding,” said study co-author CUI Yuzhu, a postdoctoral researcher at Zhejiang Lab. “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’s structure over two decades and thorough analysis are 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,” added Dr. Kazuhiro Hada from the National Astronomical Observatory of Japan. “Now anticipation has turned into certainty. This monster black hole is indeed spinning.”

Historical significance

M87 holds historical significance in the field of astronomy as it was where the first observational astrophysical jet was identified in 1918. 

Due to its relative proximity to Earth, scientists have been able to study the jet formation regions near its black hole in intricate detail using Very Long Baseline Interferometry (VLBI). 

This technique was crucial in obtaining high-resolution data, such as the recent black hole shadow images captured with the Event Horizon Telescope (EHT).

Spinning black holes

Supermassive black holes, like the one in M87, are recognized as disruptive celestial bodies, with the ability to accrete massive amounts of material and generate powerful plasma outflows, or jets. 

These jets travel at speeds approaching that of light, extending thousands of light-years into space. 

The spin of the black holes plays a crucial role in this process, extracting energy from the black hole itself, thus propelling surrounding material outwards with significant energy.

Frame-dragging 

This spin also induces a significant impact on the surrounding spacetime, dragging nearby objects along its axis of rotation, a phenomenon known as “frame-dragging.” 

This effect, predicted by Einstein’s theory, contributes to the precessional motion of the jet, providing irrefutable evidence of the black hole’s spin.

Global collaboration

Over 20 telescopes worldwide participated in the study, with contributions from China’s Tianma 65-meter and Xinjiang 26-meter radio telescopes, known for their high sensitivity and angular resolution. 

Future contributions are expected from the Shigatse 40-meter radio telescope, currently under construction by the Shanghai Astronomical Observatory, promising enhanced imaging capabilities due to its location on the Tibetan Plateau, an optimal site for sub-millimeter wavelength observations.

Future discoveries

While providing valuable insights, the research also leaves some questions unanswered, including uncertainties regarding the accretion disk’s structure and the exact value of the M87 black hole’s spin. 

Scientists expect to discover more sources with similar configurations, presenting an opportunity to improve our understanding of supermassive black holes.

More about black holes

Black holes, perhaps the most enigmatic entities in our universe, defy the boundaries of our understanding of physics and time. Born from the remnants of massive stars, they cloak themselves in a shroud of mystery and fascination, compelling scientists to incessantly unveil their secrets.

Formation and characteristics

Stars that possess about 20 times the mass of our Sun experience a dramatic demise, leading to the birth of black holes. When these stars exhaust their nuclear fuel, they can no longer support the gravitational forces pressing inward, causing them to collapse in a spectacular explosion known as a supernova.

What remains is a core where gravity pulls everything into a single point known as a singularity, around which a boundary called the event horizon forms. Once an object crosses this threshold, escape becomes impossible, even for light, thus rendering the black hole invisible against the cosmic backdrop.

Types of black holes

Scientists categorize black holes into three primary types: stellar, supermassive, and intermediate. Stellar black holes result from the gravitational collapse of massive stars and typically possess up to 20 times the mass of the Sun.

Supermassive black holes, lurking at the centers of galaxies, including our Milky Way, boast masses equivalent to millions or billions of suns. The existence of intermediate black holes, with masses between those of stellar and supermassive black holes, remains a subject of ongoing research and discussion.

Accretion disk and hawking radiation

Black holes draw nearby matter into a swirling accretion disk, where intense gravitational forces heat the material, causing it to emit X-rays and other forms of radiation. This emission allows scientists to observe and study black holes indirectly.

The concept of Hawking Radiation, proposed by physicist Stephen Hawking, suggests that black holes can also emit particles due to quantum mechanical effects near the event horizon, leading to a slow loss of mass and energy. This phenomenon implies that given enough time, black holes could eventually evaporate completely.

The relentless pursuit of knowledge by astronomers and physicists promises to uncover more layers of the mysteries enshrouded by black holes, gradually assembling the pieces of the cosmic puzzle and enriching our comprehension of the universe’s intricate tapestry.

Image Credit: Yuzhu Cui et al. 2023, Intouchable Lab@Openverse and Zhejiang Lab

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