▁as ▁the ▁e pon ym ous ▁Al pha ▁Per se i ▁Cl uster , ▁or ▁Mel otte ▁ 2 0 , ▁which ▁is ▁easily ▁visible ▁in ▁bin oc ular s ▁and ▁includes ▁many ▁of ▁the ▁f ain ter ▁stars ▁in ▁the ▁const ell ation . ▁Det erm ined ▁distance ▁using ▁the ▁trig on ometric ▁par alla x , ▁places ▁the ▁star ▁ ▁from ▁the ▁Sun . ▁ ▁Phys ical ▁properties ▁ ▁The ▁spectrum ▁of ▁Al pha ▁Per se i ▁matches ▁a ▁stell ar ▁classification ▁of ▁F 5   I b , ▁reve aling ▁it ▁to ▁be ▁a ▁super gi ant ▁star ▁in ▁the ▁latter ▁stages ▁of ▁its ▁evolution . ▁It ▁has ▁a ▁similar ▁spectrum ▁to ▁Pro cy on ▁A , ▁though ▁the ▁latter ▁star ▁is ▁much ▁less ▁l umin ous . ▁This ▁difference ▁is ▁highlight ed ▁in ▁their ▁spectral ▁design ation ▁under ▁the ▁Y erk es ▁spectral ▁classification , ▁published ▁in ▁ 1 9 4 3 , ▁where ▁stars ▁are ▁ranked ▁on ▁lum inos ity ▁as ▁well ▁as ▁spectral ▁typing . ▁Pro cy on ▁A ▁is ▁thus ▁F 5   IV , ▁a ▁sub gi ant ▁star . ▁Since ▁ 1 9 4 3 , ▁the ▁spectrum ▁of ▁Al pha ▁Per se i ▁has ▁served ▁as ▁one ▁of ▁the ▁stable ▁anchor ▁points ▁by ▁which ▁other ▁stars ▁are ▁class ified . ▁ ▁Al pha ▁Per se i ▁has ▁about ▁ 8 . 5 ▁times ▁the ▁Sun ' s ▁mass ▁and ▁has ▁expanded ▁to ▁roughly ▁ 6 0 ▁times ▁the ▁size ▁of ▁the ▁Sun .