( ( ( The energy ) ( produced ( by ( nuclear fusion ) ) ) ) ( ( heats ( ( the gases ) ( that ( ( ( surround ( ( the centers ) ( of ( the stars ) ) ) ) , ) ( causing ( them ( to ( shine brightly ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN energy)) (VP (VBN produced) (PP (IN by) (NP (JJ nuclear) (NN fusion))))) (VP (VBZ heats) (NP (NP (DT the) (NNS gases)) (SBAR (WHNP (WDT that)) (S (VP (VBP surround) (NP (NP (DT the) (NNS centers)) (PP (IN of) (NP (DT the) (NNS stars)))) (, ,) (S (VP (VBG causing) (S (NP (PRP them)) (VP (TO to) (VP (VB shine) (ADVP (RB brightly)))))))))))) (. .)))
The energy produced by nuclear fusion heats the gases that surround the centers of the stars, causing them to shine brightly.
(ROOT (S (NP (NP (JJ Nuclear) (NN fusion)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ results) (PP (RB because) (IN of) (NP (NP (JJ great) (NN pressure)) (PP (IN at) (NP (NP (DT the) (NN center)) (PP (IN of) (NP (DT a) (NN star)))))))))) (, ,)) (VP (VBZ causes) (S (NP (NNS stars)) (VP (TO to) (VP (VB shine))))) (. .)))