( ( The core ) ( ( ( ( ( is ( ( the ( innermost ( 30 % ) ) ) ( of ( ( the Sun ) ( by radius ) ) ) ) ) , ) and ) ( is ( ( where ( ( the ( nuclear reactions ) ) ( that power ) ) ) ( ( the Sun ) occur ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN core)) (VP (VBZ is) (NP (NP (DT the) (JJ innermost) (CD 30) (NN %)) (PP (IN of) (NP (NP (DT the) (NNP Sun)) (PP (IN by) (NP (NNS radius))))))) (, ,) (CC and) (VP (VBZ is) (SBAR (WHADVP (WRB where) (NP (NP (DT the) (JJ nuclear) (NNS reactions)) (NP (DT that) (NN power)))) (S (NP (DT the) (NNP Sun)) (VP (VBP occur))))) (. .)))
The core is the innermost 30% of the Sun by radius, and is where the nuclear reactions that power the Sun occur.
(ROOT (S (NP (DT The) (NN core)) (VP (VBZ is) (NP (NP (DT the) (NN sun) (POS 's)) (NN innermost) (NN layer))) (. .)))