All About Space
Active galactic nuclei
The supermassive black holes at the centres of galaxies are candidates for investigators looking for wormholes.
The motions of their orbiting stars and their gammaray output are being scrutinised for anything that doesn’t fit.
If you were able to put space-time under a powerful microscope, there’s no reason that it should appear smooth. Quantum mechanics holds that particles spontaneously appear and disappear, and the same could be true of wormholes.
Ordinary black holes
According to the Penrose diagram of a Schwarzschild black hole, an object that is already travelling faster than light when it enters a black hole will emerge in a different space, time or universe, effectively turning it into a wormhole.
One theory holds that wormholes are two entangled black holes, set back to back rather than merging into a single larger one. The ER = EPR conjecture holds that all entangled particles are joined by a wormhole, and this may go some way to unifying general relativity and quantum mechanics.