Transcript: In astronomy it’s important to distinguish between the intrinsic radiation or color of an object and the reflected radiation or color from an object. In the everyday world most objects we see are seen in the reflected light of something very hot, either sun light or the hot filament from an incandescent light for example. So the fundamental source of the radiation is a hot object at a temperature of several thousand Kelvin. A blue book is not hotter then a red book; it is just reflecting a different part of the spectrum of light from either a light bulb or the sun itself.