( ( The first ) ( ( is ( ( the core ) ( which ( is ( ( the ( innermost part ) ) ( of ( the Sun ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ first)) (VP (VBZ is) (NP (NP (DT the) (NN core)) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (NP (NP (DT the) (JJ innermost) (NN part)) (PP (IN of) (NP (DT the) (NNP Sun))))))))) (. .)))
The first is the core which is the innermost part of the Sun.
(ROOT (S (NP (DT The) (NN core)) (VP (VBZ is) (NP (NP (DT the) (NN sun) (POS 's)) (NN innermost) (NN layer))) (. .)))