Sgr A*: The Optimal Testbed of Strong-Field Gravity

TL;DR

This paper reviews current understanding and observational prospects for testing the strong-field gravity around Sgr A*, the Milky Way's central black hole, focusing on its spacetime structure and the potential to verify the Kerr metric.

Contribution

It provides a comprehensive overview of recent observational efforts and theoretical insights into the gravitational field of Sgr A* and discusses future tests of its Kerr nature.

Findings

Current observations support the Kerr black hole model for Sgr A*

Upcoming experiments aim to test deviations from the Kerr metric

Imaging and timing observations are key to understanding strong-field gravity

Abstract

The black hole in the center of the Milky Way has been observed and modeled intensely during the last decades. It is also the prime target of a number of new experiments that aim to zoom into the vicinity of its horizon and reveal the inner working of its spacetime. In this review we discuss our current understanding of the gravitational field of Sgr A* and the prospects of testing the Kerr nature of its spacetime via imaging, astrometric, and timing observations.