Perihelion is the point in the orbit of a celestial body where it is closest to the Sun. This term is commonly used in astronomy to describe the position of planets, comets, and other objects in relation to the Sun. For example, Earth reaches its perihelion around January 3 each year. At perihelion, the gravitational pull from the Sun is stronger, which can affect the speed of the orbiting body. For Earth, this means it moves slightly faster in its orbit during this time. Understanding perihelion helps scientists study the dynamics of orbits and the behavior of celestial bodies.