Phantom Glow: A Wormhole's Shadow Shines Brighter Than a Black Hole's ✛ ✦
In 2019, the image of the M87* shadow was a sensation: for the first time, humanity saw the outlines of a black hole, predicted by Schwarzschild and shrouded in myth. But what if that glowing crescent isn't a portrait of an absolute abyss, but of a cosmic portal? Wormholes, hypothetical bridges through curved spacetime, named by John Wheeler, long roamed the pages of science fiction. Now they face the rigorous test of general relativity.
Imagine two light wells. One is a black hole: it ends at the horizon, where any light disappears forever. The other is an Ellis-Bronnikov wormhole: its throat is as transparent as clear glass, through which radiation from matter on the far side seeps, acting like a gravitational lens turned inside out. It is this ghostly glow that makes its photometric portrait brighter: the central shadow is shallower, and the photon ring blazes more intensely. Numerically: the ratio of maximum to minimum brightness for the wormhole is ~2.8 versus ~1.9 for the Schwarzschild black hole, and the ring diameter is slightly wider—45 microarcseconds instead of 42. Each photon, making a full loop around the throat, reaches us with a delay, like an echo from the system's own past, layering images from different epochs of the accretion disk on top of one another.
The key to this behavior is the metric function formula, which governs gravitational redshift and ray paths: $$ f(R) = \frac{2M}{\ell}\left(\tan^{-1}\frac{R}{\ell} - \frac{\pi}{2}\right) $$ It determines how much energy light loses as it climbs out of the gravitational well. For a black hole, the horizon cuts off some trajectories; for a wormhole, it doesn't, and photons that loop around the throat multiple times reach the observer with less loss.
Today, telling the two models apart is impossible — the Event Horizon Telescope data fit both pictures. But this is not a dead end; it's a challenge. Future space interferometers, such as the Black Hole Explorer, will resolve details of the photon ring at microarcsecond resolution. Perhaps then we will see, for the first time, light that has passed through a cosmic bridge. For now, the wormhole remains a phantom quasar: it hides in the data, mimicking an ordinary black hole, thus pushing us to look for physics beyond the Standard Model — maybe the central engines of active galactic nuclei are not bottomless pits, but wide-open windows to other worlds.
The Ellis-Bronnikov wormhole, discovered in 1973, has negative mass in another universe — an exotic detail reminiscent that such objects require violation of classical energy conditions.
In the movie Interstellar, the heroes travel through a wormhole created by a supercivilization. Real models like Ellis-Bronnikov, though plagued by instability, show that a scientific basis for such portals exists.