Radio wave
Radio waves from other planets were first discovered in the 1930s by Karl Guthe Jansky, working for Bell Laboratories.  Bell was detecting noise (electronics) on radio channels, and had Jansky try to find the source of this static, or interference. After identifying noise that came from lightning, he spent much time looking into the remainder. Surprisingly, some of the interference was coming from space! This discovery eventually led astronomers to look at radio waves along with light waves to find things in the sky. These radio astronomers use giant Radio telescopes, shaped like satellite dishes, to gather and study the waves.