Johannes Kepler didn't "prove" that planets orbit in an elliptical motion in a single year. His discovery was the culmination of years of observation and calculations. Here's the breakdown:

* 1609: Kepler published his first two laws of planetary motion, which described the elliptical orbits and the relationship between a planet's orbital speed and its distance from the sun.

* 1619: Kepler published his third law of planetary motion, which related the orbital period of a planet to its average distance from the sun.

So, while it's not accurate to say he proved it in one year, 1609 is the year his findings on elliptical orbits were published, marking a significant milestone in our understanding of the universe.