( ( A ( white dwarf ) ) star )
(ROOT (NP (NP (DT A) (JJ white) (NN dwarf)) (NP (NN star))))
A white dwarf star
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (DT the) (NNP helium)) (VP (VBZ is) (VP (VBN gone))))) (, ,) (NP (DT the) (NNS stars)) (VP (VBP become) (NP (JJ white) (NNS dwarfs))) (. .)))