Remember That Black Hole They Took a Picture of? It's Spinning

The "monster black hole" just made history — again.

Mystik Spiral

An historic black hole just made another splash: it's now the first ever confirmed to be spinning.

Forming the center of its galaxy 55 million light years away, the supermassive black hole M87* was also the first to be imaged back in 2019, producing a now-iconic picture.

Since then, astronomers have plowed through more than twenty years' worth of telescope data gathered since the turn of the millennium, and have uncovered that the black hole's relativistic jet, a powerful emission of energy and particles shooting out in two directions from its center, is changing its axis of rotation in an 11-year cycle.

This motion, similar to the the wobbling of a spinning top, is known as precession. And its confirmation here, published in the journal Nature, backs up scientists' long-held hypothesis that the spin of a black hole causes these jets to precess.

"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 study coauthor Kazuhiro Hada, from the National Astronomical Observatory of Japan, in a statement about the research. "Now anticipation has turned into certainty. This monster black hole is indeed spinning."

It's a Drag

M87* is believed to be more than 6.5 billion times more massive than the Sun, and the gravity that affords is powerful enough to wield an entire galaxy and to accrete untold amounts of matter from nearby objects like stars.

When all this matter gets pulled in, it begins to orbit the black hole, like water circling a drain, forming an accretion disk. Much of that stuff eventually gets swallowed by the black hole with no complications, but some of it gets ejected at near the speed of light, forming a jet.

Behind these jets is a phenomenon known as frame-dragging, where the tremendous gravity exerted by the black hole as it spins pulls along the surrounding spacetime towards its center.

Here, the researchers observed that the rotation of the accretion disc misaligns with the spin axis of the black hole itself, explaining the jet's precession. Since a black hole can't be directly observed — though its jets, which are extremely bright, can be — this is the best evidence yet that behind its forbidding event horizon, this one is spinning.

"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," said co-author Cui Yuzhu at the Zheijang Lab in China, in the statement.

What causes a black hole to spin in the first place remains mysterious, but this discovery could prove to be essential to shedding light on that puzzle, too.

More on black holes: Astronomers Detect Mysterious Ripples in Spacetime Caused by Ancient Black Holes