Beyond the red end of the visible spectrum is infra red. This is detectable by our skin as heat radiation. A filament lamp emits light and infra red radiation (heat radiation). We can see the red light, and feel the warmth on our skin.
The sun also emits huge amounts of infra-red radiation. It is this that keeps the Earth warm and can also heat our homes for free! The above infrared image (wavelength 1083 nm) of the Sun was taken at NSO, Kitt Peak, Arizona. The darker regions show cooler, denser gas and where some of the IR is absorbed.
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