( ( Gravity ( from ( the Sun ) ) ) ( ( keeps ( all ( of ( ( the planets ) ( in ( their orbits ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Gravity)) (PP (IN from) (NP (DT the) (NNP Sun)))) (VP (VBZ keeps) (NP (NP (DT all)) (PP (IN of) (NP (NP (DT the) (NNS planets)) (PP (IN in) (NP (PRP$ their) (NNS orbits))))))) (. .)))
Gravity from the Sun keeps all of the planets in their orbits.
(ROOT (S (NP (NNP Gravity)) (VP (VBZ is) (ADJP (JJ responsible) (PP (IN for) (NP (NP (DT the) (NNS orbits)) (PP (IN of) (NP (NP (DT the) (NNS planets)) (PP (IN around) (NP (DT the) (NN sun))))))))) (. .)))
Gravity is responsible for the orbits of the planets around the sun.