Around an invisible fire, glowing gas swirls. The fire itself is hidden, but its outline can be guessed from the way the flames dance. That's roughly how astronomers 'see' black holes — not the object itself, but the superheated matter that, before plunging into the abyss, accelerates to enormous speeds and shines. In a new study, scientists built a computer model of such a 'fire' for a black hole that doesn't follow Einstein's laws but slightly modified rules, so-called gravity with Lorentz symmetry violation (a special kind of uniformity of space and time).
The portrait depends strongly on two numbers: the black hole's charge and a parameter indicating how strongly the familiar symmetry of space is broken. As this parameter grows, the black hole's shadow shrinks, as if space itself presses harder on it. The charge, on the other hand, enhances the brightness contrast: one side of the ring becomes noticeably brighter than the other. This happens because a rotating black hole twists space itself around it, like a spoon in honey. The larger the charge, the stronger the effect.
The scientists compared two types of glowing gas: one resembles a thick donut, the other a thin disk. In the second case, the ring is geometrically sharper, making it easier to separate the main image from secondary 'echo' rings. These rings arise when light bends around the black hole multiple times. The polarization of light, the direction in which the electromagnetic wave oscillates, also changes with the black hole's parameters. It mirrors the brightness pattern and reflects the geometry of curved space.
These calculations are not just a mental exercise. When telescopes like the Event Horizon Telescope capture images of black hole shadows, every pixel can be compared against a library of models to figure out what kind of object we're dealing with. So far, all observations agree with an ordinary Einsteinian black hole, but who knows what the next, even sharper images will reveal. And then, perhaps, the invisible fire will disclose new details of its nature.
The shadow of a black hole is actually larger than the black hole itself: light bends around it along a curve, and we see an enlarged dark spot — about two and a half times wider than the event horizon.
In the movie 'Interstellar,' the black hole Gargantua is shown with a bright accretion disk and a characteristic shadow — the visualization was created using real equations from general relativity.