What is infrared light and how do we use it to study the universe? Infrared radiation, or infrared light, is a type of energy that we humans can't see but can feel as heat. All objects in the universe emit some level of infrared radiation, whether hot or cold, making an infrared telescope like NASA's Spitzer Space Telescope very useful in detecting objects that might seem invisible. For more information on the Spitzer Space Telescope go to www.nasa.gov/spitzer.