( ( A ( companion star ) ) ( ( is ( ( a ( perfect source ) ) ( of ( material ( for ( a ( black hole ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN companion) (NN star)) (VP (VBZ is) (NP (NP (DT a) (JJ perfect) (NN source)) (PP (IN of) (NP (NP (NN material)) (PP (IN for) (NP (DT a) (JJ black) (NN hole))))))) (. .)))
A companion star is a perfect source of material for a black hole.
(ROOT (S (NP (NP (DT The) (JJ tidal) (NNS forces)) (PP (IN near) (NP (JJ black) (NNS holes)))) (VP (VBP are) (ADJP (RB so) (JJ great) (SBAR (S (NP (PRP they)) (VP (MD can) (ADVP (RB actually)) (VP (VB tear) (NP (NN matter)) (PP (IN from) (NP (DT a) (NN companion) (NN star))))))))) (. .)))