▁time . ▁The ▁high ▁temperature ▁of ▁Cap ella ' s ▁cor ona ▁as ▁obtained ▁from ▁the ▁first ▁cor onal ▁X - ray ▁spectrum ▁of ▁Cap ella ▁using ▁HE A O ▁ 1 ▁required ▁magnetic ▁conf in ement ▁unless ▁it ▁was ▁a ▁free - flow ing ▁cor onal ▁wind . ▁ ▁In ▁ 1 9 7 7 ▁Pro xim a ▁Cent a uri ▁is ▁discovered ▁to ▁be ▁em itting ▁high - energy ▁radiation ▁in ▁the ▁X U V . ▁In ▁ 1 9 7 8 , ▁α ▁C en ▁was ▁identified ▁as ▁a ▁low - activity ▁cor onal ▁source . ▁With ▁the ▁operation ▁of ▁the ▁Ein stein ▁observ atory , ▁X - ray ▁emission ▁was ▁recognized ▁as ▁a ▁characteristic ▁feature ▁common ▁to ▁a ▁wide ▁range ▁of ▁stars ▁covering ▁essentially ▁the ▁whole ▁H ert z spr ung - Russ ell ▁diagram . ▁The ▁Ein stein ▁initial ▁survey ▁led ▁to ▁significant ▁ins ights : ▁X - ray ▁sources ▁ab ound ▁among ▁all ▁types ▁of ▁stars , ▁across ▁the ▁H ert z spr ung - Russ ell ▁diagram ▁and ▁across ▁most ▁stages ▁of ▁evolution , ▁the ▁X - ray ▁lum inos ities ▁and ▁their ▁distribution ▁along ▁the ▁main ▁sequence ▁were ▁not ▁in ▁agreement ▁with ▁the ▁long - f av ored ▁ac oust ic ▁he ating ▁theories , ▁but ▁were ▁now ▁interpreted ▁as ▁the ▁effect ▁of ▁magnetic ▁cor onal ▁he ating , ▁and ▁stars ▁that ▁are ▁otherwise ▁similar ▁reve al ▁large ▁differences ▁in ▁their ▁X - ray ▁output ▁if ▁their ▁rotation ▁period ▁is ▁different . ▁ ▁To ▁fit