periastron
/ˌpɛrɪˈastrən
/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.