Black Hole Event Horizon Area with Angular Momentum
An event horizon is a boundary in spacetime beyond which events cannot affect an outside observer.
The event horizon area increases roughly quadratically with the mass and the angular momentum.
Formula
![Copy to Clipboard QuantityVariable["A", "Area"] == 4*Pi*((Quantity[1, "SpeedOfLight"^(-2)]*QuantityVariable["J", "AngularMomentum"]^2)/QuantityVariable["M", "Mass"]^2 + (Quantity[1, "GravitationalConstant"/"SpeedOfLight"^2]*QuantityVariable["M", "Mass"] + Sqrt[(Quantity[-1, "SpeedOfLight"^(-2)]*QuantityVariable["J", "AngularMomentum"]^2)/QuantityVariable["M", "Mass"]^2 + Quantity[1, "GravitationalConstant"^2/"SpeedOfLight"^4]*QuantityVariable["M", "Mass"]^2])^2)](https://www.wolframcloud.com/objects/resourcesystem/marketplacestorage/resources/b17/b17005d8-8d91-4d4e-9aa5-c1aea792b1f4/Webpage/FormulaImage.png)
| symbol | description | physical quantity |
|---|---|---|
| A | event horizon area | "Area" |
| J | angular momentum | "AngularMomentum" |
| M | mass | "Mass" |
Forms
Examples
Get the resource:
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| Out[1]= | ![]() |
Get the formula:
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Use some values:
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![FormulaData[
ResourceObject[
"Black Hole Event Horizon Area with Angular Momentum"], \
{QuantityVariable["J","AngularMomentum"] ->
Quantity[1.`*^-10, "Joules" "Seconds"],
QuantityVariable["M","Mass"] -> Quantity[2.`*^30, "Kilograms"]}]](images/b17/b17005d8-8d91-4d4e-9aa5-c1aea792b1f4-io-3-i.en.gif)