( ( ( ( ( ( Neutron ( Star ( Neutron stars ) ) ) ( are ( ( the ( super ( dense remains ) ) ) ( of ( massive stars ) ) ) ) ) , ) and ) ( they ( ( are often ) ( what ( is ( ( left behind ) ( after ( a ( supernova explosion ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNP Neutron) (NNP Star) (NNP Neutron) (NNS stars)) (VP (VBP are) (NP (NP (DT the) (JJ super) (JJ dense) (NNS remains)) (PP (IN of) (NP (JJ massive) (NNS stars)))))) (, ,) (CC and) (S (NP (PRP they)) (VP (VBP are) (ADVP (RB often)) (SBAR (WHNP (WP what)) (S (VP (VBZ is) (VP (VBN left) (PRT (RP behind)) (PP (IN after) (NP (DT a) (NN supernova) (NN explosion))))))))) (. .)))
Neutron Star Neutron stars are the super dense remains of massive stars , and they are often what is left behind after a supernova explosion.
(ROOT (S (NP (NN Neutron) (NNS stars)) (VP (VBP are) (NP (NP (DT the) (NNS corpses)) (PP (IN of) (NP (ADJP (VBN left) (RP over)) (NN supernova) (NNS explosions))))) (. .)))