The Electromagnetic Spectrum
In fact, what our eyes can see (what astronomers call optical light) is only one small part of the range of possible types of "light". The full range of different types is called the Electromagnetic Spectrum.
At the low-energy end of the Electromagnetic Spectrum we find Radio waves. As we move towards higher energies, we pass through Microwaves, Infra-red light and into the Optical part of the spectrum. Further still takes us into Ultra-violet light, X-rays and all the way up to Gamma-rays.
Everything we know about the universe comes from observing the electromagnetic spectrum.
You may want to read more about the electromagnetic spectrum and the nature of light.