# The brightest point in accretion disk and black hole spin: implication to the image of black hole M87*

## TL;DR

This paper introduces a new method to estimate black hole spin from high-resolution images by analyzing the brightest point in the accretion disk relative to the black hole silhouette, applied to M87*.

## Contribution

It presents a novel approach to determine black hole spin using the position of the brightest accretion disk point in high-resolution images.

## Key findings

- Estimated M87* black hole spin as a=0.75±0.15
- Established a numerical relation between silhouette position and spin
- Demonstrated the method's applicability to Event Horizon Telescope data

## Abstract

We propose the simple new method for extracting the value of the black hole spin from the direct high-resolution image of black hole by using a thin accretion disk model. In this model the observed dark region on the first image of the supermassive black hole in the galaxy M87, obtained by the Event Horizon Telescope, is a silhouette of the black hole event horizon. The outline of this silhouette is the equator of the event horizon sphere. The dark silhouette of the black hole event horizon is placed within the expected position of the black hole shadow, which is not revealed on the first image. We calculated numerically the relation between the observed position of the black hole silhouette and the brightest point in the thin accretion disk, depending on the black hole spin. From this relation we derive the spin of the supermassive black hole M87*, $a=0.75\pm0.15$.