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Astrophysics/angular momentum of black hole


Dear Mr. Gort.
I have a question, its very simple I guess.
I have already know about penrose process which extracted angular momentum from black hole and adds mass into black hole so the black hole getting more stable (please correct me if i'm wrong). By the way, Can the energy from black hole's angular momentum change into black hole's mass (E/c^2) by another condition (not by external perturbation)?

thank you for always help me, you're awesome

Hello Norma,

You are correct - most descriptions of the Penrose process talk about accreting matter in the ergosphere, and infalling negative energy particles will tend to slow down the spin, increase the mass, and adds to "stability" of the black hole.

However, there is nothing to prohibit a solitary black hole (without any accretion from an external source) to also exhibit the Penrose process through virtual pair production (similar to Hawking radiation). In this process, virtual pairs created in the ergosphere could also carry negative energy to the spinning black hole and slow it down and increasing its mass. That's equivalent to taking its rotational energy and converting it to increased mass of the black hole (through virtual particle production).

Prof. James Gort  


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James Gort


Questions on observational astronomy, optics, and astrophysics. Specializing in the evolution of stars, variable stars, supernovae, neuton stars/pulsars, black holes, quasars, and cosmology.


I was a professional astronomer (University of Texas, McDonald Observatory), lecturer at the Adler Planetarium, professor of astrophysics, and amateur astronomer for 42 years. I have made numerous telescopes, and I am currently building one of the largest private observatories in Canada.

StarDate, University of Texas, numerous Journal Publications

B.A. Physics and Astronomy M.Sc. Physics Ph.D. Astrophysics

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