( ( A ( neutron star ) ) ( ( is ( ( the ( imploded core ) ) ( of ( ( a ( massive star ) ) ( produced ( by ( a ( supernova explosion ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN neutron) (NN star)) (VP (VBZ is) (NP (NP (DT the) (JJ imploded) (NN core)) (PP (IN of) (NP (NP (DT a) (JJ massive) (NN star)) (VP (VBN produced) (PP (IN by) (NP (DT a) (NN supernova) (NN explosion)))))))) (. .)))
A neutron star is the imploded core of a massive star produced by a supernova explosion.
(ROOT (S (NP (NP (DT The) (NN core)) (PP (IN of) (NP (DT a) (NN star)))) (VP (VBZ collapses) (PP (IN during) (NP (DT a) (NN supernova))) (, ,) (S (VP (VBG forming) (NP (DT a) (NN neutron) (NN star))))) (. .)))