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The Kerr metric or Kerr geometry describes the geometry of empty spacetime around a rotating uncharged axially symmetric black hole with a quasispherical event horizon.The Kerr metric is an exact solution of the Einstein field equations of general relativity; these equations are highly non-linear, which makes exact solutions very difficult to find.
The no-hair theorem (which is a hypothesis) states that all stationary black hole solutions of the Einstein–Maxwell equations of gravitation and electromagnetism in general relativity can be completely characterized by only three independent externally observable classical parameters: mass, angular momentum, and electric charge.
A black hole is a region of spacetime where gravity is so strong that nothing, not even light, can escape it. [2] Albert Einstein's theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. [3] [4] The boundary of no escape is called the event horizon.
In isotropic coordinates, the McVittie metric is given by [1] = (() / + / ()) + (+ / ()) () (+), where is the usual line element for the euclidean sphere, M is identified as the mass of the massive object, () is the usual scale factor found in the FLRW metric, which accounts for the expansion of the space-time; and () is a curvature parameter related to the scalar curvature of the 3-space as
A rotating black hole is a black hole that possesses angular momentum. In particular, it rotates about one of its axes of symmetry. All celestial objects – planets, stars , galaxies, black holes – spin. [1] [2] [3] The boundaries of a Kerr black hole relevant to astrophysics. Note that there are no physical "surfaces" as such.
While in a non-rotating black hole the singularity occurs at a single point in the model coordinates, called a "point singularity", in a rotating black hole, also known as a Kerr black hole, the singularity occurs on a ring (a circular line), known as a "ring singularity". Such a singularity may also theoretically become a wormhole. [18]
Pulsars had already been discovered and black holes were no longer considered mere textbook curiosities. [15] Cygnus X-1, the first solid black-hole candidate, was discovered by the Uhuru X-ray space telescope in 1971. [1] Jeremy Bernstein described it as "one of the great papers in twentieth-century physics." [14]
In physics, black hole thermodynamics [1] is the area of study that seeks to reconcile the laws of thermodynamics with the existence of black hole event horizons.As the study of the statistical mechanics of black-body radiation led to the development of the theory of quantum mechanics, the effort to understand the statistical mechanics of black holes has had a deep impact upon the ...