noun. That point in the path of a body having orbital motion in which it is at its least distance from the center of gravity of the system. In the case of the solar system the pericenter of an orbit is called the perihelion. Compare apocenter.

noun. The periapsis, the point of closest approach of an astronomical object in an elliptical orbit to its center of attraction.

"A star called S2 (star) follows an elliptical orbit with a period of 15.2 years and a pericenter (closest) distance of 17 light hours from the central object."

apocenter  

periastron  perihelion  

periapsis  perigee