( This ( ( is ( because ( stars ( ( get ( their energy ) ) ( from ( ( ( the process ) ( of ( nuclear fusion ) ) ) ( -LRB- ( ( ( two nuclei ) ( ( ( joining ( to ( form ( one ( heavier nucleus ) ) ) ) ) and ) ( releasing ( ( large amounts ) ( of energy ) ) ) ) ) -RRB- ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (SBAR (IN because) (S (NP (NNS stars)) (VP (VBP get) (NP (PRP$ their) (NN energy)) (PP (IN from) (NP (NP (DT the) (NN process)) (PP (IN of) (NP (JJ nuclear) (NN fusion))) (PRN (-LRB- -LRB-) (NP (NP (CD two) (NNS nuclei)) (S (VP (VP (VBG joining) (S (VP (TO to) (VP (VB form) (NP (CD one) (JJR heavier) (NN nucleus)))))) (CC and) (VP (VBG releasing) (NP (NP (JJ large) (NNS amounts)) (PP (IN of) (NP (NN energy)))))))) (-RRB- -RRB-)))))))) (. .)))
This is because stars get their energy from the process of nuclear fusion (two nuclei joining to form one heavier nucleus and releasing large amounts of energy).
(ROOT (S (PP (IN In) (NP (DT the) (JJ nuclear) (NN fusion) (NN process))) (, ,) (NP (CD two) (JJ light) (NNS nuclei)) (VP (VBP combine) (S (VP (TO to) (VP (VB produce) (NP (NP (DT a) (JJR heavier) (NN nucleus)) (CC and) (NP (JJ great) (NN energy))))))) (. .)))