Testing the No-Hair Theorem with Sgr A*

Abstract

The no-hair theorem characterizes the fundamental nature of black holes in general relativity. This theorem can be tested observationally by measuring the mass and spin of a black hole as well as its quadrupole moment, which may deviate from the expected Kerr value. Sgr A*, the supermassive black hole at the center of the Milky Way, is a prime candidate for such tests thanks to its large angular size, high brightness, and rich population of nearby stars. In this review I discuss a new theoretical framework for a test of the no-hair theorem that is ideal for imaging observations of Sgr A* with very-long baseline interferometry (VLBI). The approach is formulated in terms of a Kerr-like spacetime that depends on a free parameter and is regular everywhere outside of the event horizon. Together with the results from astrometric and timing observations, VLBI imaging of Sgr A* may lead to a secure test of the no-hair theorem.

8 pages, 7 figures, invited review for Advances in Astronomy, Special Issue: "Seeking for the Leading Actor on the Cosmic Stage: Galaxies versus Supermassive Black Holes"

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Cited by in corpus (22)

• Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A${}^{\ast }$
• Testing black hole candidates with electromagnetic radiation
• Regular Black Hole Metric with Three Constants of Motion
• Sgr A* and General Relativity
• No-Hair Theorem in the Wake of Event Horizon Telescope
• Systematic Study of Event Horizons and Pathologies of Parametrically Deformed Kerr Spacetimes
• Shadow of a Charged Rotating Non-Commutative Black Hole
• Probing the Lorentz Symmetry Violation Using the First Image of Sagittarius A*: Constraints on Standard-Model Extension Coefficients
• The non-integrability of the Zipoy-Voorhees metric
• Asymptotically flat, parameterized black hole metric preserving Kerr symmetries
• Strong gravitational lensing by a rotating non-Kerr compact object
• A Symmetric Integrator for non-integrable Hamiltonian Relativistic Systems
• Rotating non-Kerr black hole and energy extraction
• Curious case of gravitational lensing by binary black holes: a tale of two photon spheres, new relativistic images and caustics
• Higher dimensional non-Kerr black hole and energy extraction
• Inner Accretion Disk Edges in a Kerr-Like Spacetime
• Non-Linear Effects in Non-Kerr spacetimes
• Constants of motion in stationary axisymmetric gravitational fields
• Reconstruction of Static Black Hole Images Using Simple Geometric Forms
• A Metric for Testing the Nature of Black Holes
• Mind the Resonances: Final stages of accretion into bumpy black holes
• Probing Fundamental Physics with Gravitational Waves