( ( Star ( cluster ( and ( galaxy dynamics ) ) ) ) . )
(ROOT (NP (NP (NNP Star)) (NP (NN cluster) (CC and) (NN galaxy) (NNS dynamics)) (. .)))
Star cluster and galaxy dynamics.
(ROOT (S (NP (DT A) (NN galaxy)) (VP (VBZ is) (VP (RBS best) (VBN described) (PP (IN as) (NP (NP (DT a) (NN cluster)) (PP (IN of) (NP (NP (NNS billions)) (PP (IN of) (NP (NNS stars))))))))) (. .)))