In theory, black holes of all sizes eventually evaporate, due to quantum processes close to the event horizon that result in net emissions that appear to come from the black hole (but actually originate just outside it), and which also reduce its mass.

This suggests that subject to rotation and charge, all black holes that evaporate in isolation, in theory behave identically or at least probably very similarly in their final moments.

But what does theory say about the nature of those emissions in the last seconds/milliseconds/attoseconds of an evaporating black hole's life? For example, power output/intensity, spectrum, periodicity if any (eg if rotating), and division between EM and gravitational?

And what time scale might we focus on, in theory, if we wanted to observe interesting end-of-life phenomena? (By which I mean, for inspiralling BH we observe on the order of the last few tens of seconds with most phenomena appearing more visibly in the last 10 or so ms, what would the "most interesting observational interval" be for end of life BH?)

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    $\begingroup$ A BH still has many years of existence left by the time it's hot enough to emit more interesting particles than photons. See the Hawking radiation calculator and set the Peak photons to 511 keV, the rest energy of electrons & positrons. At that stage, the temperature is around 1.5 billion kelvin, but the luminosity is only 54 kW, and the event horizon size is subatomic. $\endgroup$
    – PM 2Ring
    Commented Apr 21, 2021 at 20:34


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