I What Happens When a Black Hole Reaches the End of Its Life?

[nolxiii]

When a black hole is mostly evaporated and it starts to evaporate faster and faster, what will this look like? How big when they start to emit visible light and how long from then until finally gone? Will these be like cosmic level bursts or quiet fizzle?

 

[mfb]

They start emitting visible light when their Schwarzschild radius is of the order of the wavelength of visible light. Here is a calculator. A Schwarzschild radius of 500 nm corresponds to a mass of 3*10¹⁷ tonnes, a power of 3 nW and a lifetime of 10²⁸ times the age of the universe.

Black holes have to much smaller to evaporate today, with an initial mass of a few hundred million tonnes and an initial power of 10 GW emitted as light, gravitons, neutrinos, electrons, muons, pions and a few heavier particles and their antiparticles. In their last second they release an energy corresponding to a few hundred tonnes (don't trust the calculator that late as it doesn't consider the emission of massive particles). Much smaller than many other astrophysical events but still orders of magnitude larger than the largest nuclear weapons we have.

 

[nolxiii]

ty!