When we think “telescope”, we picture peering through a viewfinder or viewing images of the stars. However, visible light is only a small part of the electromagnetic spectrum; we can learn much about our galaxy by viewing visible light’s less frequent older brother, the radio wave. Radio telescopes are the technological descendants of actual radios (like the one in your car!). Karl Jansky, who worked for Bell Telephone Laboratories, created a large radio antenna to test for sources of static which would interfere with radio telephone calls. He identified static from nearby thunderstorms, but heard a constant “faint hiss.” This “faint hiss” was radiation from the universe, concentrated in the Milky Way galaxy.
Radio telescopes typically look like huge dishes with an antenna. Currently, astronomers often use radio interferometers: series of connected radio telescopes. While radio interferometers are used to observe information about galaxies, planets, and nebulae, some of the most groundbreaking work in radio astronomy is taking place examining cosmic background radiation. Cosmic background radiation is the thermal radiation left behind from the Big Bang. Differences in radio frequencies of cosmic background radiation reveals early differences in temperature which dictated how stars and galaxies form. Thus, radio telescopes can reveal how and why the universe formed the way it did.
