A black hole is like a pot that slowly boils away. Its surface emits particles, a process known as Hawking radiation. The hotter the pot, the faster it empties. But what if the pot is not ordinary, but has a double bottom — capable of turning into a passage to another place? Physicists studied two families of such 'tricky' black holes, which under certain conditions become wormholes.
Previously, the evaporation of these objects was estimated approximately, like gauging the boiling rate by eye, from the bubbles. In the new work, the scientists replaced the estimates with a direct calculation: they numerically traced how light particles and massless electrons (neutrinos) break through the surface. It turned out that near an ordinary black hole, the old estimates still work, but the closer to the wormhole state, the more they lie — sometimes by hundreds and thousands of times.
The most striking example is the Simpson–Visser black hole. If you estimate its half-life using the old formulas, you get one number. But the direct calculation shows that it actually lives 85 times longer. This is important for understanding how compact objects at the centers of galaxies behave and whether wormholes can exist in nature.
Such a recalculation is not just a refinement. It shows that without direct numerical modeling, one cannot trust predictions about the fate of black holes evolving toward wormholes. Their evaporation is a delicate process where every radiation frequency plays a role, and 'by eye' approximations are powerless here.
If a black hole the size of a tennis ball turned into a wormhole, its radiation would be fainter than the glow of a single firefly.
In the movie 'Interstellar,' a wormhole serves as a portal to another galaxy; this work shows that the transition from a black hole to a wormhole might be not explosive but quiet and almost imperceptible.