Hawking Evaporation

Gravitational micro lensing rules out primordial black holes with masses over 10 to the minus 10 or 10 to theminus 9 solar masses, basically a tiny, tiny fraction of the mass of the sun. So let's take it from the opposite direction and say like what's the smallest black hole we could be considering here? And to do that we have to talk about a phenomena called Hawking Evaporation. This is probably Stephen Hawking's most famous discovery or at least one of his greatest hits. If you take a black hole and look at its surface, you'll find that that surface radiates like a hot object.