Final answer:
A planet moves slowest at the aphelion, which is the point in its orbit that is farthest from the Sun.
Step-by-step explanation:
In the context of our solar system, a planet moves the slowest at the point in its orbit that is farthest from the Sun. This point is known as the aphelion.
According to Kepler's laws of planetary motion, planets orbit the Sun in elliptical orbits, and their orbital speeds vary depending on their distance from the Sun.
At the aphelion, the planet is at its greatest distance from the Sun and moves at its slowest speed. Conversely, the point where the planet is nearest to the Sun is called the perihelion, and here the planet will move at its fastest.