Half of the major axis is termed a semi-major axis. The equation for Kepler’s Third Law is P² = a³, so the period of a planet’s orbit (P) squared is equal to the size semi-major axis of the ...

Kepler’s second law says that a line joining a planet and ... and the orbit’s semi-major axis in astronomical units, the equation simplifies to period squared equals semi-major axis cubed.

Johannes Kepler was a 16th century astronomer who established three laws which govern the motion of planets around the sun. These are known as Kepler’s laws of planetary motion. These laws ...