Infrared light is a form of electromagnetic radiation having wavelengths between red light and microwaves. Due to its longer wavelength, infrared light behaves somewhat differently than do visible wavelengths. It is invisible to our eyes. infrared light can’t pass through common window glass while white light does. But infrared can pass through black (opaque) plastic – like that found in trashcan liners.
Infrared light is used by astronomers to help see deep inside nebulae – the clouds of gas and dust out of which new stars are continually being formed in our galaxy and beyond. If you can’t see it – how do astronomers? The answer is with technology. Sensors are built that are capable of detecting radiation in infrared bands. The Spitzer Space Telescope has two imaging devices aboard – IRAC and MIPS. These “cameras” can detect IR wavelengths between 3.6 and 24 microns.