( ( ( The ( radial velocity ) ) ( of ( ( ( a star ) away ) ( ( ( from or ) towards ) ( the observer ) ) ) ) ) ( ( can ( be ( determined ( by ( measuring ( ( the ( red ( shift ( or ( blue shift ) ) ) ) ) ( of ( its spectrum ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ radial) (NN velocity)) (PP (IN of) (NP (NP (DT a) (NN star)) (ADVP (RB away)) (PP (IN from) (CC or) (IN towards) (NP (DT the) (NN observer)))))) (VP (MD can) (VP (VB be) (VP (VBN determined) (PP (IN by) (S (VP (VBG measuring) (NP (NP (DT the) (JJ red) (NN shift) (CC or) (JJ blue) (NN shift)) (PP (IN of) (NP (PRP$ its) (NN spectrum)))))))))) (. .)))
The radial velocity of a star away from or towards the observer can be determined by measuring the red shift or blue shift of its spectrum.
(ROOT (S (NP (NNP Red-shift)) (VP (VBZ refers) (PP (TO to) (NP (NP (DT a) (NN shift)) (PP (IN toward) (NP (NN red))))) (PP (IN in) (NP (NP (DT the) (NN spectrum)) (PP (IN from) (NP (NNS stars)))))) (. .)))