Definition of periastron in English:

periastron

noun

Astronomy
  • The point nearest to a star in the path of a body orbiting that star.

    • ‘Also, relativistic advance of periastron has been studied and confirmed in certain binary stars with elliptical orbits.’

Origin

Mid 19th century: from peri- ‘around’ + Greek astron ‘star’, on the pattern of perigee and perihelion.

Pronunciation

periastron

/ˌperēˈastrən//ˌpɛriˈæstrən/