In fact, until the dawn of X-ray astronomy in the 1960s, we didn't know of the existence of many celestial objects because we simply couldn't see them with optical telescopes. Today, astronomers are seeing the invisible. X-ray astronomers in particular are observing the most fiery, cataclysmic events since the Big Bang. Light, or electromagnetic radiation, comes in many forms. There are radio waves, infrared light, ultraviolet light, X-rays, and gamma rays.
Visible light occupies a sliver between the infrared and ultraviolet.
Oddly enough, visible light is the smallest band of radiation. To our eyes, visible light seems like the entire universe. Yet there is much more out there. The Electromagnetic Spectrum Different types of objects in the universe emit different types of radiation. Our Sun is a rather obvious source of visible light.