In 1609 Johannes Kepler gave only two laws by analyzing astronomical observation Tycho Brahe and later after few years he discovered the third law which was published 1619.
1) Law of orbit: The path of planets around the sun is elliptical in shape sun with sun located at one focus.
2) Law of Areas: The imaginary line connecting the planet and the sun sweeps equal areas in equal interval of time.
3) Law of periods:The square of time period of any planet directly proportional to the cube of semi major axis of the orbit.
T2 =k a3
k = constant