per·i·as·tron 
(pĕr′ē-ăstrən, -trŏn)
(pĕr′ē-ăstrən, -trŏn)n. pl. per·i·as·tra (-trə)
The point at which an object is closest to the center of mass of the star it is orbiting.
[PERI- + Greek astron, star (probably on the model of PERIHELION); see ster-3 in the Appendix of Indo-European roots.]