( ( A ( neutron star ) ) ( ( is ( ( an ( ( extremely dense ) ( , ( ( rapidly rotating ) star ) ) ) ) ( that ( remains ( after ( some ( supernova explosions ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN neutron) (NN star)) (VP (VBZ is) (NP (NP (DT an) (ADJP (RB extremely) (VBN dense)) (, ,) (ADJP (RB rapidly) (VBN rotating)) (NN star)) (SBAR (WHNP (WDT that)) (S (VP (VBZ remains) (PP (IN after) (NP (DT some) (NN supernova) (NNS explosions)))))))) (. .)))
A neutron star is an extremely dense, rapidly rotating star that remains after some supernova explosions.
(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))))) (. .)))