( They ( ( are ( one ( of ( ( the ( three ( main types ) ) ) ( of ( galaxy ( originally ( described ( by ( ( Edwin Hubble ) ( in 1936 ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT the) (CD three) (JJ main) (NNS types)) (PP (IN of) (NP (NP (NN galaxy)) (VP (ADVP (RB originally)) (VBN described) (PP (IN by) (NP (NP (NNP Edwin) (NNP Hubble)) (PP (IN in) (NP (CD 1936)))))))))))) (. .)))
They are one of the three main types of galaxy originally described by Edwin Hubble in 1936.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD three) (NNS types)) (PP (IN of) (NP (NNS galaxies))))) (. .)))