▁visual ▁observations ▁yields ▁a ▁very ▁accurate ▁orbit . ▁ ▁The ▁spectrum ▁of ▁component ▁B , ▁the ▁outer ▁star ▁of ▁the ▁triple , ▁cannot ▁be ▁detected . ▁The ▁lum inos ity ▁contribution ▁from ▁ σ ▁Ori ▁B ▁can ▁be ▁measured ▁and ▁it ▁is ▁likely ▁to ▁be ▁a ▁B 0 - 2 ▁main ▁sequence ▁star . ▁Its ▁visual ▁magnitude ▁of ▁ 5 . 3 1 ▁is ▁similar ▁to ▁ σ ▁Ori ▁Ab ▁and ▁so ▁it ▁should ▁be ▁easily ▁visible , ▁but ▁it ▁is ▁spec ulated ▁that ▁its ▁spectral ▁lines ▁are ▁highly ▁bro aden ed ▁and ▁invisible ▁against ▁the ▁back drop ▁of ▁the ▁other ▁two ▁stars . ▁The ▁orbit ▁of ▁component ▁B ▁has ▁been ▁calculated ▁precisely ▁using ▁the ▁N PO I ▁and ▁CHAR A ▁arrays . ▁The ▁combined ▁or bits ▁of ▁the ▁three ▁stars ▁together ▁give ▁a ▁par alla x ▁significantly ▁more ▁precise ▁than ▁the ▁H IP PAR CO S ▁par alla x . ▁ ▁The ▁incl in ations ▁of ▁the ▁two ▁or bits ▁are ▁known ▁accur ately ▁enough ▁to ▁calculate ▁their ▁relative ▁incl ination . ▁The ▁two ▁orb ital ▁plan es ▁are ▁within ▁ 3 0 ° ▁of ▁being ▁orthogonal , ▁with ▁the ▁inner ▁orbit ▁being ▁pro grade ▁and ▁the ▁outer ▁retro grade . ▁Although ▁slightly ▁surprising , ▁this ▁situation ▁is ▁not ▁necessarily ▁rare ▁in ▁triple ▁systems . ▁ ▁Mass ▁dis cre p ancy ▁The ▁masses ▁of ▁these ▁three ▁component ▁stars ▁can ▁be ▁calculated ▁using : ▁spect ro scop ic ▁calculation ▁of ▁the ▁surface ▁gravity ▁and ▁hence ▁a ▁spect ro scop ic ▁mass ; ▁comparison