Black Hole Or Singularity?
The ultracompact object at the center of our Galaxy appears to be either a black hole or a horizonless singularity. The latter type of ultracompact, a horizonless singularity, can arise in two ways. If an ultracompact object has sufficient angular momentum energy then it is a “naked” (i.e., horizonless) singularity, and it is a ring singularity rather than a point singularity.
Alternatively, if one is already inside of the event horizon of a black hole, the ultracompact object at the center is a singularity.
Although it is a long shot, at best, I think it is possible that the Event Horizon Telescope results might conflict with expectations for a standard event horizon, and be more consistent with a horizonless ring singularity.
Makes for an interesting test of expectations.