▁as ▁May rit ▁AB . ▁ ▁Cl uster ▁ ▁The ▁ σ ▁Or ion is ▁cluster ▁is ▁part ▁of ▁the ▁Ori ▁O B 1 b ▁stell ar ▁association , ▁commonly ▁referred ▁to ▁as ▁Or ion ' s ▁B elt . ▁ ▁The ▁cluster ▁was ▁not ▁recogn ised ▁until ▁ 1 9 9 6 ▁when ▁a ▁population ▁of ▁pre - main ▁sequence ▁stars ▁was ▁discovered ▁around ▁ σ ▁Ori . ▁ ▁Since ▁then ▁it ▁has ▁been ▁extens ively ▁studied ▁because ▁of ▁its ▁clos eness ▁and ▁the ▁lack ▁of ▁inter stell ar ▁ext inction . ▁ ▁It ▁has ▁been ▁calculated ▁that ▁star ▁formation ▁in ▁the ▁cluster ▁began ▁ 3 ▁million ▁years ▁( my r ) ▁ago ▁and ▁it ▁is ▁approximately ▁ 3 6 0 ▁pc ▁away . ▁ ▁In ▁the ▁central ▁arc - min ute ▁of ▁the ▁cluster ▁five ▁particularly ▁bright ▁stars ▁are ▁visible , ▁label led ▁A ▁to ▁E ▁in ▁order ▁of ▁distance ▁from ▁the ▁bright est ▁component ▁ σ ▁Ori ▁A . ▁ ▁The ▁closest ▁pair ▁AB ▁are ▁only ▁separated ▁by ▁ 0 . 2 " ▁- ▁ 0 . 3 " ▁but ▁were ▁discovered ▁with ▁a ▁ 1 2 " ▁teles cope . ▁ ▁An ▁inf ra red ▁and ▁radio ▁source , ▁I RS 1 , ▁ 3 . 3 " ▁from ▁ σ ▁Ori ▁A ▁that ▁was ▁considered ▁to ▁be ▁a ▁patch ▁of ▁ne bul os ity ▁has ▁been ▁resolved ▁into ▁two ▁sub sol ar ▁stars . ▁ ▁There ▁is ▁an ▁associated ▁variable ▁x - ray ▁source ▁that ▁is ▁assumed ▁to