Watching a black hole flicker in time

Black hole imaging has entered a new era since the Event Horizon Telescope (EHT) captured the first-ever image of the supermassive black hole in galaxy M87*. But those famous pictures only show a still frame of what is, in reality, a wildly dynamic scene. The gas swirling around a black hole flickers, twists, and shifts with time — and understanding that motion could reveal new clues about gravity and the nature of spacetime itself.

In a recent study, researchers from China have developed a powerful way to simulate how a black hole’s appearance changes over time, focusing on a special kind of black hole called a rotating regular (Hayward) black hole. Unlike the traditional “Kerr” black hole, these regular black holes have a nonsingular core, avoiding the infinite-density problem at the center.

The team built a computer model that mimics the turbulent behavior of matter around such black holes using a technique borrowed from statistics called a spatio-temporal random field. In simple terms, this allows them to generate realistic, time-varying patterns of light and shadow—like watching the glow of the accretion disk shimmer and shift as time passes. They also included the effects of light taking different paths around the black hole, so the resulting images look more like what telescopes such as the EHT would actually see.

What’s striking is that their simulated images naturally show the same kind of behavior seen in real observations of M87*, such as a rotation or shifting of the bright ring around the black hole over time. In standard Kerr models, such motion requires delicate tuning of the plasma environment. Here, however, it emerges naturally from the geometry and random fluctuations of the spacetime model.

Because this new method is much faster than full-blown magnetohydrodynamic simulations, scientists can explore many different black hole configurations—varying spin, magnetic charge, and viewing angle—without the enormous computing costs. This makes it an ideal tool for studying non-Kerr black holes and testing whether Einstein’s theory might need adjustments near extreme gravitational limits.

Looking ahead, the researchers hope to expand their model to include light polarization, radiative feedback, and other physical effects. As future telescopes like the next-generation EHT (ngEHT) deliver even sharper and faster black hole movies, tools like this will be key to decoding what we’re really seeing when we watch the shadows of black holes dance.

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