Black holes are real astronomical entities supported by observational evidence. They possess magnetic poles and can emit jets of charged particles due to interactions with their surrounding accretion disks, despite the singularity at their core. The Kerr metric describes rotating black holes, which can have event horizons that rotate at significant speeds, affecting the dynamics of nearby matter. The theoretical understanding of black holes, particularly the relationship between accretion disks and jets, remains an area of active research.
PREREQUISITESAstronomers, astrophysicists, and students of theoretical physics interested in black hole research and the dynamics of cosmic phenomena.
The radiation we receive from quasars and microquasars comes not from the black holes themselves, but instead originates in the accretion disks which surround them
(see Figure 1). In these accretion disks, angular momentum is gradually removed by some presumably (although not necessarily [48]) dissipative process, causing matter to spiral down into the black hole, converting its gravitational energy into heat, and then, by various processes, radiating this energy.7 The radiation subsequently leaks through the disk, escapes from its surface, and travels along trajectories curved (in space) by the strong gravity of the black hole, eventually reaching our telescopes...However, the theoretical
understanding of disks and jets has largely proceeded separately and the physical link between the two still remains uncertain...
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Space-like singularities are a feature of non-rotating uncharged black-holes, while time-like singularities are those that occur in charged or rotating black hole exact solutions. Both of them have the following property:
geodesic incompleteness: Some light-paths or particle-paths cannot be extended beyond a certain proper-time or affine-parameter (affine parameter is the null analog of proper time).
It is still an open question whether time-like singularities ever occur in the interior of real charged or rotating black holes, or whether they are artifacts of high symmetry and turn into spacelike singularities when realistic perturbations are added.
Rotating black holes are described by the Kerr metric...The event horizon is rotating as though it were a solid body, so can be characterized by an angular velocity or rotation rate in RPM. For a 10 solar mass black hole rotating at the maximal rate, it is rotating at about 10^4 radians/second or about 10^5 RPM. Larger black holes will rotate at lower RPM rates, but at the maximal rotation rate, a point on the equator of the event horizon is always rotating at 1/2 the speed of light.