What gravitational effect allows a planet to travel faster at perihelion than at aphelion?

The gravitational effect that causes a planet to travel faster at perihelion than at aphelion is primarily linked to the concept of gravitational attraction in Newton's Law of Universal Gravitation. When a planet is at perihelion, which is the closest point to the Sun in its elliptical orbit, it experiences a stronger gravitational pull from the Sun compared to when it is at aphelion, the farthest point in its orbit.

This increased gravitational pull at perihelion results in a higher orbital speed due to the conservation of angular momentum. As the planet moves in its elliptical path, it accelerates when it is nearer to the Sun and decelerates as it moves farther away. This relationship exemplifies how gravitational force affects orbital dynamics, leading to variations in speed throughout the planet's orbit.

In contrast, the other options do not accurately represent how gravitational forces operate in the context of planetary motion and orbital mechanics. This understanding is crucial when studying celestial mechanics and the behavior of planets within our solar system.