▁optical ▁syn ch ro tr on ▁emission ▁are ▁strong . ▁Its ▁overall ▁X - ray ▁lum inos ity ▁riv als ▁the ▁optical ▁emission ▁and ▁could ▁be ▁that ▁of ▁a ▁non ther mal ▁pl asma . ▁However , ▁the ▁C rab ▁Neb ula ▁appears ▁as ▁an ▁X - ray ▁source ▁that ▁is ▁a ▁central ▁freely ▁expand ing ▁ball ▁of ▁dil ute ▁pl asma , ▁where ▁the ▁energy ▁content ▁is ▁ 1 0 0 ▁times ▁the ▁total ▁energy ▁content ▁of ▁the ▁large ▁visible ▁and ▁radio ▁portion , ▁obtained ▁from ▁the ▁unknown ▁source . ▁ ▁The ▁" D ivid ing ▁Line " ▁as ▁giant ▁stars ▁evol ve ▁to ▁become ▁red ▁gi ants ▁also ▁coinc ides ▁with ▁the ▁Wind ▁and ▁Cor onal ▁D ivid ing ▁L ines . ▁To ▁explain ▁the ▁drop ▁in ▁X - ray ▁emission ▁across ▁these ▁div iding ▁lines , ▁a ▁number ▁of ▁models ▁have ▁been ▁proposed : ▁ ▁low ▁transition ▁region ▁dens ities , ▁leading ▁to ▁low ▁emission ▁in ▁cor ona e , ▁ ▁high - dens ity ▁wind ▁ext inction ▁of ▁cor onal ▁emission , ▁ ▁only ▁cool ▁cor onal ▁loops ▁become ▁stable , ▁ ▁changes ▁in ▁a ▁magnetic ▁field ▁structure ▁to ▁that ▁an ▁open ▁topology , ▁leading ▁to ▁a ▁decrease ▁of ▁magnet ically ▁conf ined ▁pl asma , ▁or ▁ ▁changes ▁in ▁the ▁magnetic ▁dynam o ▁character , ▁leading ▁to ▁the ▁disapp earance ▁of ▁stell ar ▁fields ▁leaving ▁only ▁small - scale , ▁tur bul ence - generated ▁fields ▁among ▁red ▁gi ants . ▁ ▁Anal yt ical ▁X - ray