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 paper, 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.
展开▼
机译：无毛定理描述了广义相对论中黑洞的基本性质。该定理可以通过测量黑洞的质量和自旋以及其四极矩来进行观察性测试，该质量可能会偏离预期的Kerr值。 Sgr A *是银河系中心的超大质量黑洞，由于其大的角度大小，高的亮度以及附近恒星的数量众多，因此是此类测试的主要候选对象。在本文中，我讨论了一种用于测试无毛定理的新理论框架，该理论对通过非常长的基线干涉仪（VLBI）对Sgr A *的成像观察非常理想。该方法是根据类似于Kerr的时空制定的，该时空取决于自由参数，并且在事件范围之外的任何地方都是规则的。 Sgr A *的VLBI成像与天文观测和定时观测的结果一起可能会导致对无毛定理的安全测试。
展开▼
