Testing the No-Hair Theorem with Sgr A*

Tim Johannsen

doi:10.1155/2012/486750

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arXiv · 1105.5645

Testing the No-Hair Theorem with Sgr A*

Tim Johannsen

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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.

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Tim Johannsen. 2011-05-27. Testing the No-Hair Theorem with Sgr A*. https://doi.org/10.1155/2012%2F486750

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