Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Kryptid on 28/04/2017 20:31:45
-
In an uncharged black hole, it's random which particle in a virtual particle pair crosses the event horizon and which escapes to infinity, right? So about an equal number of electrons and positrons fall into the hole as those that escape. Does this scenario change when the black hole has a net electric charge? If it was, say, negatively charged, wouldn't the field attract positrons while repelling electrons? Wouldn't this cause a bias in the ratio of infalling positrons to infalling electrons? Since positively charged particles are entering the hole more often than negatively charged particles, wouldn't the black hole's charge diminish over time?
-
virtual particle pair crosses the event horizon and which escapes to infinity...electrons and positrons
The distribution of energy of the particles coming out of a black hole depends on the black hole's effective temperature.
A Solar-mass black hole has an effective temperature of 60 nanokelvins, so the most likely particles to come out would be very long-wavelength (low energy) radio photons and neutrinos (plus maybe gravitons). All are uncharged.
A micro black hole (about to explode) would emit light with photon energy around 2 eV. The peak energy emitted has a wavelength about 16 times the diameter of the black hole event horizon. Unfortunately, we do not currently have a good estimate of the energy of a neutrino (or graviton) of the same wavelength, so its a bit hard to estimate the mix of particles that would be emitted. But these are all uncharged, so it will not affect the charge of the black hole.
An electron has an energy around 510000 eV/c2. We know of no charged particles with lower energy. These would only be emitted from a micro black hole which is in the process of exploding, in which case all of its internal mass would be released.
https://en.wikipedia.org/wiki/Hawking_radiation#Black_hole_evaporation
wouldn't the black hole's charge diminish over time?
I expect there would be a slight bias in which virtual particles are reabsorbed - the black hole as a whole has a lower potential energy if its electric field is lower.
However, a charged black hole would preferentially attract charges of the opposite polarity from surrounding space, so its charge would decline over time, even without charged virtual particles.
-
The distribution of energy of the particles coming out of a black hole depends on the black hole's effective temperature.
A Solar-mass black hole has an effective temperature of 60 nanokelvins, so the most likely particles to come out would be very long-wavelength (low energy) radio photons and neutrinos (plus maybe gravitons). All are uncharged.
A micro black hole (about to explode) would emit light with photon energy around 2 eV. The peak energy emitted has a wavelength about 16 times the diameter of the black hole event horizon. Unfortunately, we do not currently have a good estimate of the energy of a neutrino (or graviton) of the same wavelength, so its a bit hard to estimate the mix of particles that would be emitted. But these are all uncharged, so it will not affect the charge of the black hole.
An electron has an energy around 510000 eV/c2. We know of no charged particles with lower energy. These would only be emitted from a micro black hole which is in the process of exploding, in which case all of its internal mass would be released.
https://en.wikipedia.org/wiki/Hawking_radiation#Black_hole_evaporation
wouldn't the black hole's charge diminish over time?
I expect there would be a slight bias in which virtual particles are reabsorbed - the black hole as a whole has a lower potential energy if its electric field is lower.
However, a charged black hole would preferentially attract charges of the opposite polarity from surrounding space, so its charge would decline over time, even without charged virtual particles.
That makes sense. I was even wondering at what temperature electrons would emerge.