( ( As ( ( the comet ) ( approaches ( the sun ) ) ) ) ( , ( ( solar radiation ) ( ( ( ( melts ( the ice ) ) , ) ( ( causing ( dust ( particles ( and ( rock fragments ) ) ) ) ) ( to ( ( ( separate ( from ( the ( comet nucleus ) ) ) ) , ) ( forming ( the ( ( visually radiant ) tail ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (DT the) (NN comet)) (VP (VBZ approaches) (NP (DT the) (NN sun))))) (, ,) (NP (JJ solar) (NN radiation)) (VP (VBZ melts) (NP (DT the) (NN ice)) (, ,) (S (VP (VBG causing) (NP (NN dust) (NNS particles) (CC and) (NN rock) (NNS fragments)) (S (VP (TO to) (VP (VB separate) (PP (IN from) (NP (DT the) (JJ comet) (NN nucleus))) (, ,) (S (VP (VBG forming) (NP (DT the) (ADJP (RB visually) (JJ radiant)) (NN tail)))))))))) (. .)))
As the comet approaches the sun, solar radiation melts the ice, causing dust particles and rock fragments to separate from the comet nucleus, forming the visually radiant tail.
(ROOT (S (NP (JJ Comet) (NNS tails)) (VP (ADVP (RB always)) (VBP point) (PRT (RP away)) (PP (IN from) (NP (NP (DT the) (NN sun)) (PP (RB instead) (IN of) (S (VP (VBG trailing) (PP (IN behind) (NP (DT the) (ADJP (JJ comet) (PP (IN because) (NP (NN dust) (NNS particles)))) (NN recoil))))))))) (. .)))