Definitions

1. adjective

relating to or characteristic of a periastron, especially in astronomy.

“The periastral motion of the star was studied extensively by astronomers.”

2. noun

an event, especially in astronomy, at which the orbit of a celestial body, such as a planet or star, is at its closest point to a central body, such as the Sun.

“The periastral passage of the comet marked the beginning of the celestial spectacle.”