ly ) ▁spin ning ▁body , ▁such ▁as ▁a ▁typical ▁planet ▁or ▁star . ▁ ▁Ex plan ation ▁According ▁to ▁general ▁relativ ity , ▁in ▁its ▁weak - field ▁and ▁slow - m otion ▁linear ized ▁approximation , ▁a ▁slowly ▁spin ning ▁body ▁indu ces ▁an ▁additional ▁component ▁of ▁the ▁gravit ational ▁field ▁that ▁acts ▁on ▁a ▁freely - fall ing ▁test ▁particle ▁with ▁a ▁non - central , ▁gravit om agnet ic ▁Lor ent z - like ▁force . ▁ ▁Among ▁its ▁consequences ▁on ▁the ▁particle ' s ▁orb ital ▁motion ▁there ▁is ▁a ▁small ▁correction ▁to ▁Ke pler ' s ▁third ▁law , ▁namely ▁ ▁where ▁T K ep ▁is ▁the ▁particle ' s ▁period , ▁ ▁M ▁is ▁the ▁mass ▁of ▁the ▁central ▁body , ▁and ▁a ▁is ▁the ▁sem im aj or ▁axis ▁of ▁the ▁particle ' s ▁el lipse . ▁ ▁If ▁the ▁orbit ▁of ▁the ▁particle ▁is ▁circular ▁and ▁lies ▁in ▁the ▁equ atorial ▁plane ▁of ▁the ▁central ▁body , ▁the ▁correction ▁is ▁ ▁where ▁S ▁is ▁the ▁central ▁body ' s ▁angular ▁momentum ▁and ▁c ▁is ▁the ▁speed ▁of ▁light ▁in ▁vac u um . ▁ ▁Part icles ▁orbit ing ▁in ▁opposite ▁directions ▁experience ▁gravit om agnet ic ▁corre ctions ▁T G vm ▁with ▁opposite ▁signs , ▁so ▁that ▁the ▁difference ▁of ▁their ▁orb ital ▁periods ▁would ▁cancel ▁the ▁standard ▁Ke pler ian ▁terms ▁and ▁would ▁add ▁the ▁gravit om agnet ic ▁ones . ▁Note ▁that ▁the ▁+ ▁sign ▁occurs ▁for ▁particle ' s ▁cor ot