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However, it is hypothesized that light entering a singularity would similarly have its geodesics terminated, thus making the naked singularity look like a black hole. [17] [18] [19] Disappearing event horizons exist in the Kerr metric, which is a spinning black hole in a vacuum, if the angular momentum () is high
The parameters of the singularity are M=1, a²+Q²=2M². The singularity is viewed from its equatorial plane at θ=90° (edge on). Comparison with an extremal black hole with M=1, a²+Q²=1M². Disappearing event horizons exist in the Kerr metric, which is a spinning black hole in a vacuum.
Black holes of stellar mass form when massive stars collapse at the end of their life cycle. After a black hole has formed, it can grow by absorbing mass from its surroundings. Supermassive black holes of millions of solar masses (M ☉) may form by absorbing other stars and merging with other black holes, or via direct collapse of gas clouds.
Like black holes, white holes have properties such as mass, charge, and angular momentum.They attract matter like any other mass, but objects falling towards a white hole would never actually reach the white hole's event horizon (though in the case of the maximally extended Schwarzschild solution, discussed below, the white hole event horizon in the past becomes a black hole event horizon in ...
A photograph of a black hole at the center of galaxy M87. The black hole is outlined by emission from hot gas swirling around it under the influence of strong gravity near its event horizon.
The point at which tidal forces destroy an object or kill a person will depend on the black hole's size. For a supermassive black hole, such as those found at a galaxy's center, this point lies within the event horizon, so an astronaut may cross the event horizon without noticing any squashing and pulling, although it remains only a matter of ...
The final-state proposal [66] suggests that boundary conditions must be imposed at the black-hole singularity, which, from a causal perspective, is to the future of all events in the black-hole interior. This helps reconcile black-hole evaporation with unitarity but contradicts the intuitive idea of causality and locality of time-evolution.
For black holes, this manifests as Hawking radiation, and the larger question of how the black hole possesses a temperature is part of the topic of black hole thermodynamics. For accelerating particles, this manifests as the Unruh effect , which causes space around the particle to appear to be filled with matter and radiation.