( ( Neutron ( Star ( Neutron stars ) ) ) ( ( are ( formed ( when ( ( ( the ( collapsed core ) ) ( left ( by ( a supernova ) ) ) ) ( ( causes ( its ( ( protons and ) electrons ) ) ) ( to ( combine ( into ( only neutrons ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Neutron) (NNP Star) (NNP Neutron) (NNS stars)) (VP (VBP are) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (JJ collapsed) (NN core)) (VP (VBN left) (PP (IN by) (NP (DT a) (NN supernova))))) (VP (VBZ causes) (NP (PRP$ its) (NNS protons) (CC and) (NNS electrons)) (S (VP (TO to) (VP (VB combine) (PP (IN into) (NP (JJ only) (NNS neutrons))))))))))) (. .)))
Neutron Star Neutron stars are formed when the collapsed core left by a supernova causes its protons and electrons to combine into only neutrons.
(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))))) (. .)))