( ( A comet ) ( ( is ( ( a ( small ( , ( icy ( celestial body ) ) ) ) ) ( that ( orbits ( around ( the sun ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN comet)) (VP (VBZ is) (NP (NP (DT a) (JJ small) (, ,) (JJ icy) (JJ celestial) (NN body)) (SBAR (WHNP (WDT that)) (S (VP (VBZ orbits) (PP (IN around) (NP (DT the) (NN sun)))))))) (. .)))
A comet is a small, icy celestial body that orbits around the sun.
(ROOT (S (NP (DT The) (NNS planets)) (VP (VB orbit) (PRT (RP around)) (NP (DT the) (NN sun))) (. .)))