A duo of theoretical physicists from Fudan University, Shanghai, has proposed a very intriguing hypothesis; supermassive black holes at the center of normal galaxies, including our own Milky Way, may not actually be black holes at all. Instead, they could be wormholes. The paper detailing their theory has been published as a preprint edition and will be soon available in General Relativity and Quantum Cosmology.
Wormholes, although not yet proven to exist, are theorized to be channels, or shortcuts, between either different parts of the universe or even two different universes in a Multiverse model. Wormholes are composed of two mouths, which could be black holes, interconnected by a throat. The possibility of their existence was even suggested by Einstein and his theory of general relativity mathematically predicts their existence.
Sagittarius A* (SgrA*) was first observed back in 1974 as an object at the center of the Milky Way that was found to be emitting radio waves. Further investigation of SgrA* revealed telltale signs that the object was a black hole, for example the behavior of nearby stars, and astronomers have been convinced of this classification ever since.
Although we cannot observe a black hole directly since light is unable to get out, they can be detected by other means. For example, observations of SgrA* reveal plasma orbiting near the event horizon. If SgrA* is a wormhole we would also expect to see orbiting plasma blobs, however, they should differ in appearance since wormholes are predicted to be smaller than supermassive black holes.
Furthermore, wormholes could help to explain the conundrum that even young galaxies are equipped with objects that are believed to be supermassive black holes. These black holes should take a considerable length of time to achieve such size; therefore, theoretically they should not and cannot exist in new galaxies, according to the authors of this paper. Wormholes on the other hand could theoretically appear relatively quickly.
The researchers believe that their theory could be put to the test in a few years when the VLTI instrument GRAVITY is added to the European Southern Observatory in Chile. One of the main objectives of GRAVITY is to discern whether the Galactic Center harbors a black hole of four million solar masses. However, it should also be able to reveal whether the wormhole prediction is correct because the orbiting plasma will look dramatically different dependent on whether the object is a wormhole or a black hole since wormholes would have much smaller photon capture spheres.
For now, we will have to wait patiently until that data is obtained. However, if these predictions are correct, they would certainly represent a major and extremely exciting discovery.