Cosmic Censorship in Sgr A* and M87*: Observationally Excluding Naked Singularities

TL;DR

This paper uses observational data from the Event Horizon Telescope to strongly support the existence of event horizons in supermassive black holes and rules out many naked singularity models under certain conditions.

Contribution

It demonstrates that a broad class of naked singularities can be observationally excluded based on geodesic properties, strengthening evidence for black hole event horizons.

Findings

Naked singularities with inner turning points for geodesics are excluded.

Observational constraints support the existence of event horizons.

Many naked singularity models are ruled out under the assumptions.

Abstract

The imaging of Sagittarius A* (Sgr A*) and the supermassive black hole at the center of Messier 87 (M87*) by the Event Horizon Telescope constrains the location and nature of emission from these objects. Coupled with flux limits from the near-infrared through the ultraviolet, the attendant size constraints provide strong evidence for the absence of an accretion-powered photosphere, and therefore for the existence of an event horizon about an astrophysical black hole. Here, we demonstrate that a broad class of naked singularities exhibit inner turning points for time-like geodesics, and therefore may generically be excluded, regardless of the nature and unknown physical impact of singularity itself, subject to the single weak assumption that the its nongravitational impact is localized to its immediate vicinity. While we restrict our attention to static, spherically symmetric spacetimes, we are nevertheless able to exclude or constrain a large number of commonly invoked naked singularity spacetimes in this way.