Infrared is a form of light that is invisible to our eyes
but which we can feel as heat. Infrared telescopes detect heat
associated with star formation inside dark cosmic clouds.
There are many forms of light that we can’t see with
just our eyes, from gamma rays emitted by nuclear reactions
to radio waves that we use in wireless communications. In the
middle of this range is visible light.
Why does infrared light penetrate cosmic dust clouds? Infrared
light has a longer wavelength that travels through dust easily,
while shorter wavelength visible light is scattered by interstellar
For more on infrared astronomy, including the complete "Infrared
Cosmos at the SIRTF Science Center.