( ( As ( we ( now know ) ) ) ( , ( however ( , ( ( ( ( ( the sun ) , ) ( not ( the earth ) ) ) , ) ( ( is ( ( the center ) ( of ( the ( solar system ) ) ) ) ) . ) ) ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (PRP we)) (ADVP (RB now)) (VP (VBP know)))) (, ,) (ADVP (RB however)) (, ,) (NP (NP (DT the) (NN sun)) (, ,) (NP (RB not) (DT the) (NN earth)) (, ,)) (VP (VBZ is) (NP (NP (DT the) (NN center)) (PP (IN of) (NP (DT the) (JJ solar) (NN system))))) (. .)))
As we now know, however, the sun, not the earth, is the center of the solar system.
(ROOT (S (NP (DT The) (NN sun)) (VP (VBZ is) (VP (VBN considered) (NP (NP (DT the) (NN center)) (PP (IN of) (NP (DT the) (JJ solar) (NN system)))))) (. .)))