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  2. Event horizon - Wikipedia

    en.wikipedia.org/wiki/Event_horizon

    In astrophysics, an event horizon is a boundary beyond which events cannot affect an outside observer. Wolfgang Rindler coined the term in the 1950s. [1]In 1784, John Michell proposed that gravity can be strong enough in the vicinity of massive compact objects that even light cannot escape. [2]

  3. Black hole - Wikipedia

    en.wikipedia.org/wiki/Black_hole

    The ergosphere of a black hole is a volume bounded by the black hole's event horizon and the ergosurface, which coincides with the event horizon at the poles but is at a much greater distance around the equator. [116] Objects and radiation can escape normally from the ergosphere.

  4. Sagittarius A* - Wikipedia

    en.wikipedia.org/wiki/Sagittarius_A*

    Size comparison between Sagittarius A* and M87*. The diameter of Sagittarius A* is smaller than the orbit of Mercury. On May 12, 2022, the first image of Sagittarius A* was released by the Event Horizon Telescope Collaboration. The image, which is based on radio interferometer data taken in 2017, confirms that the object contains a black hole.

  5. Hawking radiation - Wikipedia

    en.wikipedia.org/wiki/Hawking_radiation

    (Although nothing can travel through space faster than light, space itself can infall at any speed.) [6] Once matter is inside the event horizon, all of the matter inside falls inevitably into a gravitational singularity, a place of infinite curvature and zero size, leaving behind a warped spacetime devoid of any matter; [verification needed] a ...

  6. Schwarzschild radius - Wikipedia

    en.wikipedia.org/wiki/Schwarzschild_radius

    As the Schwarzschild radius is linearly related to mass, while the enclosed volume corresponds to the third power of the radius, small black holes are therefore much more dense than large ones. The volume enclosed in the event horizon of the most massive black holes has an average density lower than main sequence stars.

  7. Black hole thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Black_hole_thermodynamics

    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 ...

  8. Cosmological horizon - Wikipedia

    en.wikipedia.org/wiki/Cosmological_horizon

    A cosmological horizon is a measure of the distance from which one could possibly retrieve information. [1] This observable constraint is due to various properties of general relativity, the expanding universe, and the physics of Big Bang cosmology. Cosmological horizons set the size and scale of the observable universe. This article explains a ...

  9. De Sitter–Schwarzschild metric - Wikipedia

    en.wikipedia.org/wiki/De_Sitter–Schwarzschild...

    It is spherically symmetric and it has a cosmological horizon surrounding any observer, and describes an inflating universe. The Schwarzschild solution is the simplest spherically symmetric solution of the Einstein equations with zero cosmological constant, and it describes a black hole event horizon in otherwise empty space.