We don't have synonyms for periapses yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are periapsis, periapse and periapts.
(n) :
Misspelling of periapsis. [(astronomy, astrophysics) The point of a body's (elliptical) orbit in a 2-body gravitational system such that the distance between the two bodies (measured from their respective centres of mass) is at its minimum.]
(n) :
Misspelling of periapsis. [(astronomy, astrophysics) The point of a body's (elliptical) orbit in a 2-body gravitational system such that the distance between the two bodies (measured from their respective centres of mass) is at its minimum.]