▁magnitude ▁of ▁− 6 . ▁ ▁History ▁▁ ▁The ▁magnitude ▁system ▁dates ▁back ▁roughly ▁ 2 0 0 0 ▁years ▁to ▁the ▁Greek ▁astronom er ▁Hi pp arch us ▁( or ▁the ▁Alexand rian ▁astronom er ▁P to le my — re ferences ▁vary ) ▁who ▁class ified ▁stars ▁by ▁their ▁apparent ▁bright ness , ▁which ▁they ▁saw ▁as ▁size ▁( m agn itude ▁means ▁" b ign ess , ▁size "). ▁To ▁the ▁una ided ▁eye , ▁a ▁more ▁prominent ▁star ▁such ▁as ▁Si ri us ▁or ▁Ar ct urus ▁appears ▁larger ▁than ▁a ▁less ▁prominent ▁star ▁such ▁as ▁M izar , ▁which ▁in ▁turn ▁appears ▁larger ▁than ▁a ▁truly ▁faint ▁star ▁such ▁as ▁Al cor . ▁In ▁ 1 7 3 6 , ▁the ▁math ematic ian ▁John ▁Ke ill ▁described ▁the ▁ancient ▁n aked - ey e ▁magnitude ▁system ▁in ▁this ▁way : ▁The ▁fixed ▁Stars ▁appear ▁to ▁be ▁of ▁different ▁B ign esses , ▁not ▁because ▁they ▁really ▁are ▁so , ▁but ▁because ▁they ▁are ▁not ▁all ▁equally ▁distant ▁from ▁us . ▁Those ▁that ▁are ▁nearest ▁will ▁excel ▁in ▁L ust re ▁and ▁B ign ess ; ▁the ▁more ▁remote ▁Stars ▁will ▁give ▁a ▁f ain ter ▁Light , ▁and ▁appear ▁smaller ▁to ▁the ▁E ye . ▁Hence ▁arise ▁the ▁Distribution ▁of ▁Stars , ▁according ▁to ▁their ▁Order ▁and ▁D ign ity , ▁into ▁Class es ; ▁the ▁first ▁Class ▁containing ▁those ▁which ▁are ▁nearest ▁to ▁us , ▁are ▁called ▁Stars ▁of ▁the ▁first ▁Magn itude ; ▁those ▁that