( ( for ( ( the masses ) ( of ( stars ( , ( clusters ( , ( and galaxies ) ) ) ) ) ) ) ) . )
(ROOT (FRAG (PP (IN for) (NP (NP (DT the) (NNS masses)) (PP (IN of) (NP (NNS stars) (, ,) (NNS clusters) (, ,) (CC and) (NNS galaxies))))) (. .)))
for the masses of stars, clusters, and galaxies.
(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))))))))) (. .)))