When a massive star dies, you either get a neutron star, or a black hole. From my lecture, neutron star are extremely hot object, with temperature around 10E11 to 10E12 kelvin. I'd assume black hole created from a similar process with just more mass, wouldn't have temperature any lower. But I also read that black hole have temperature proportional to their size, which for solar sized one is measured in nano kelvin. So my question is, how does a black hole get rid of its birthing creation temperature?