▁in ▁stars ▁with ▁less ▁than ▁si xty ▁times ▁the ▁mass ▁of ▁Jup iter ▁( ). ▁In ▁this ▁way , ▁the ▁rate ▁of ▁l ith ium ▁de ple tion ▁can ▁be ▁used ▁to ▁calculate ▁the ▁age ▁of ▁the ▁star . ▁ ▁Types ▁ ▁Several ▁types ▁of ▁T TS s ▁exist : ▁Class ical ▁T ▁Ta uri ▁star ▁( CT TS ) ▁We ak - line ▁T ▁Ta uri ▁star ▁( WT TS ) ▁N aked ▁T ▁Ta uri ▁star ▁( NT TS ), ▁which ▁is ▁a ▁subset ▁of ▁W T TS . ▁ ▁R ough ly ▁half ▁of ▁T ▁Ta uri ▁stars ▁have ▁circum stell ar ▁dis ks , ▁which ▁in ▁this ▁case ▁are ▁called ▁pro top lan et ary ▁disc s ▁because ▁they ▁are ▁probably ▁the ▁pro gen itors ▁of ▁planet ary ▁systems ▁like ▁the ▁Sol ar ▁System . ▁Circ um stell ar ▁disc s ▁are ▁estimated ▁to ▁diss ip ate ▁on ▁times cal es ▁of ▁up ▁to ▁ 1 0 ▁million ▁years . ▁Most ▁T ▁Ta uri ▁stars ▁are ▁in ▁binary ▁star ▁systems . ▁In ▁various ▁stages ▁of ▁their ▁life , ▁they ▁are ▁called ▁Young ▁St ell ar ▁Object s ▁( Y SO s ). ▁It ▁is ▁thought ▁that ▁the ▁active ▁magnetic ▁fields ▁and ▁strong ▁solar ▁wind ▁of ▁Alf v én ▁waves ▁of ▁T ▁Ta uri ▁stars ▁are ▁one ▁means ▁by ▁which ▁angular ▁momentum ▁gets ▁transferred ▁from ▁the ▁star ▁to ▁the ▁pro top lan et ary ▁disc . ▁A ▁T ▁Ta uri ▁stage ▁for ▁the ▁Sol ar ▁System ▁would ▁be ▁one ▁means