( ( A ( neutron star ) ) ( ( is ( ( a ( small ( , ( powerful body ) ) ) ) ( left ( behind ( when ( ( a ( massive star ) ) ( dies ( in ( a ( supernova explosion ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN neutron) (NN star)) (VP (VBZ is) (NP (NP (DT a) (JJ small) (, ,) (JJ powerful) (NN body)) (VP (VBN left) (PP (IN behind) (SBAR (WHADVP (WRB when)) (S (NP (DT a) (JJ massive) (NN star)) (VP (VBZ dies) (PP (IN in) (NP (DT a) (NN supernova) (NN explosion)))))))))) (. .)))
A neutron star is a small, powerful body left behind when a massive star dies in 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))))) (. .)))