Light is a familiar everyday phenomena that we take for granted.
When the Sun or other stars shine, we see light. When we turn on a lamp, we see light.
Technically, light is an energy disturbance in the air. Oscillating electric and magnetic fields radiate energy in waves.
The wavelengths and frequency fall in the middle of the electromagnetic spectrum, between ultraviolet and infrared rays. It so happens that our eyes detect radiation at those wavelengths and frequencies in the form of light.
Different elements, and the combinations of elements that make up molecules, emit radiation in different ranges of the electromagnetic spectrum.
Nitrogen-based ammonia, for example, tends to emit microwaves. We cannot see ammonia in space with an optical telescope, but it can be found using a special microwave telescope.
Neon radiation, however, is detected as light. Think of all the neon signs in all the store and restaurant windows you’ve seen.
Technology now allows astronomers to study radiation across the whole electromagnetic spectrum.
Research into all the different kinds of radiation provides far more information, and raises many more questions, about the universe than studying light alone.