# What is the temperature of the black hole?

Are black holes hot or cold? I was thinking because I wanted to know if there any human sustainable temperature so we can travel in it.

• Forget about traveling there. There's no solid surface to stand on, not to mention that doing so would turn you into a puddle of neutrons anyways. – John Dvorak Dec 4 '19 at 19:27
• What kind of energy is present in there? – Shaun Dec 4 '19 at 19:29
• Related question: astronomy.stackexchange.com/q/26427/24157 – user24157 Dec 4 '19 at 20:27

$$T=\frac{hc^3}{16\pi^2GMk_B}$$
Where $$h$$ is the Planck constant, $$c$$ is the speed of light, $$G$$ is Newton's gravitational constant, $$M$$ is the mass of the black hole, and $$k_B$$ is the Boltzmann constant.
If you are talking about the temperature of the event horizon, then it depends on the mass. Super-massive black holes have a temperature of $$1.4 \times 10^{-14}$$ Kelvin while a solar mass black hole has a temperature of only $$6.0 \times 10^{-8}$$ Kelvin. This temperature comes from the proposed Hawking radiation of black holes$$^1$$. The reference below gives some temperatures for very small black holes.