# Colour Temperature and the thermal temperature [duplicate]

I understand that Colour Temperature correlates with the object's thermal temperature, such as a red-hot piece of iron being ~360c and the incandescent bulb filament is about 2500c.

Why are sources of light, such as LEDs and florescent tubes, that emit white to white-blue light (which according to Colour Temperature, would be around 4500+c) cool, or nowhere near 4500c, when touched?

Also, why is the sky considered 10,000k? Especially if the surface of the sun is only ~5770k?

## marked as duplicate by V.F., Jon Custer, Bill N, Kyle Kanos, John RennieOct 15 '18 at 10:28

So when we say that the sky is $$10\,000\ \rm K$$, we don't mean that it's actually that hot: it's actually that an ideal black-body at $$10\,000\ \rm K$$ would radiate light of the same color. After that, you can read about Rayleigh scattering to describe why the sky is blue.