Karl Jansky was an American engineer and radio astronomer, best known for his pioneering work in radio astronomy. In the 1930s, while working for Bell Telephone Laboratories, he discovered cosmic radio waves emitted from the Milky Way galaxy. His findings laid the groundwork for the field of radio astronomy, which studies celestial objects through their radio frequency emissions. Jansky's most significant contribution was the identification of the first radio source, which he named Sagittarius A*, located in the center of the Milky Way. His work opened new avenues for understanding the universe and led to the development of advanced radio telescopes, revolutionizing the way astronomers observe and study space.