1. Radio Astronomy

We'll end our list of astronomical discoveries made without a telescope with something completely different -- radio waves in outer space. Although we mainly think of the ones that we generate and transmit for communication -- radar, GPS, computers and more -- radio waves also occur naturally. Essentially, the term just means a specific type of wave on the electromagnetic spectrum (which includes X-rays, light, ultraviolet and several other types).

In 1865, Scottish mathematician and physicist James Clerk Maxwell predicted radio waves, and their existence was proven when German physicist Heinrich Hertz generated them in a laboratory in 1887. The field of radio astronomy was born 44 years later when American physicist and radio engineer Karl Jansky discovered that there were radio waves coming from the Milky Way. Jansky worked for Bell Laboratories and was seeking possible sources of static interference with voice transmissions. After long observation and studying astronomical maps, he discovered that one source was cosmic radio waves.

Jansky published a paper on the subject and wanted to explore it further, but Bell Labs wasn't interested. Some speculate that Jansky would have won a Nobel Prize for his research had he not died at the young age of 44 due to a heart condition. Today, the unit of measurement for the strength of radio sources in the field of radio astronomy is called a Jansky in his honor.