How does a planet’s angular velocity change during an elliptical orbit?

In an elliptical orbit, a planet’s angular velocity does not remain constant; it varies throughout its path.12

According to Kepler’s second law of planetary motion, a planet sweeps out equal areas in equal intervals of time. Because the planet’s distance from the Sun changes as it moves along its elliptical path, its orbital speed must also change to satisfy this law. Specifically:12

• Near perihelion: When the planet is at its closest point to the Sun, it moves at a higher-than-average velocity. Consequently, its angular velocity is at its maximum.12
• Near aphelion: When the planet is at its farthest point from the Sun, it moves at a lower-than-average velocity, resulting in its minimum angular velocity.12

This variation is a direct consequence of the law of conservation of angular momentum, which dictates that because the gravitational force acts along the radius vector between the Sun and the planet, it exerts no torque, keeping the planet's angular momentum constant throughout its orbit.13