Photo credit: Alain R, via Wikimedia Commons.
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.