Event horizon image within black hole shadow

TL;DR

This paper proposes that the true image of a black hole, as seen by distant observers, is its event horizon rather than the shadow, influenced by gravitational lensing of infalling matter, which could be observable with future telescopes.

Contribution

It introduces the concept that the event horizon, rather than the shadow, forms the observable image of a black hole, emphasizing gravitational lensing effects of infalling matter.

Findings

Event horizon image is formed by highly red-shifted photons near the horizon.

The event horizon appears as a gravitationally lensed projection on the celestial sphere.

Black holes can be viewed from both front and back sides simultaneously.

Abstract

We argue that a genuine image of the black hole viewed by a distant observer is not its shadow, but a more compact event horizon image probed by the luminous matter plunging into black hole. The external border of the black hole shadow is washed out by radiation from matter plunging into black hole and approaching the event horizon. This effect will crucially influence the results of future observations by the Event Horizon Telescope. We show that gravitational lensing of the luminous matter plunging into black hole provides the possibility for visualization of the event horizon. The lensed image of the event horizon is formed by the highly red-shifted photons emitted by the plunging matter very near the black hole event horizon and detected by a distant observer. The resulting event horizon image is a gravitationally lensed projection on the celestial sphere of the whole black hole event horizon sphere. Seemingly, black holes are the unique objects in the Universe which may be viewed by distant observers at once from both the front and back sides.