Answer :
The astronomer who spent 20 years plotting the positions of the planets is Kepler. Johannes Kepler was a German astronomer who meticulously studied the movements of the planets and developed three laws of planetary motion known as Kepler's Laws. These laws describe the motion of planets around the Sun, including the shapes of their orbits and the time it takes for them to complete their orbits.
Kepler's work was essential in advancing our understanding of the solar system and laid the foundation for Isaac Newton's later work on gravity and celestial mechanics. By analyzing data collected by Tycho Brahe, Kepler was able to derive his laws, which revolutionized the field of astronomy.
In summary, Johannes Kepler is the astronomer who spent two decades plotting the positions of the planets, contributing significantly to our knowledge of the cosmos.
