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(Supermassive black holes up to 21 billion (2.1 × 10 10) M ☉ have been detected, such as NGC 4889.) [16] Unlike stellar mass black holes, supermassive black holes have comparatively low average densities. (Note that a (non-rotating) black hole is a spherical region in space that surrounds the singularity at its center; it is not the ...
A black hole with the mass of a car would have a diameter of about 10 −24 m and take a nanosecond to evaporate, during which time it would briefly have a luminosity of more than 200 times that of the Sun. Lower-mass black holes are expected to evaporate even faster; for example, a black hole of mass 1 TeV/c 2 would take less than 10 −88 ...
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]
The first [1] is given by = where M BH is the mass of the black hole, σ is the stellar velocity dispersion of the host bulge, and G is the gravitational constant. The second definition [ 2 ] is the radius at which the enclosed mass in stars equals twice M BH , i.e. M ⋆ ( r < r h ) = 2 M BH . {\displaystyle M_{\star }(r<r_{h})=2M_{\text{BH}}.}
Gravitational time dilation is closely related to gravitational redshift, [4] in which the closer a body emitting light of constant frequency is to a gravitating body, the more its time is slowed by gravitational time dilation, and the lower (more "redshifted") would seem to be the frequency of the emitted light, as measured by a fixed observer.
Although charged black holes with r Q ≪ r s are similar to the Schwarzschild black hole, they have two horizons: the event horizon and an internal Cauchy horizon. [8] As with the Schwarzschild metric, the event horizons for the spacetime are located where the metric component diverges; that is, where + = =
Scientists made that point anew on Monday in a study that used observations of a ferocious class of black holes called quasars to demonstrate "time dilation" in the early universe, showing how ...
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.