( ( Because ( of this ) ) ( , ( ( black holes ) ( ( ( are ( most easily ) ) ( detected ( by ( ( ( ( observing ( their effects ) ) ( on ( ( other bodies ) ( of matter ) ) ) ) , ) ( for ( ( example , ) ( a ( companion star ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Because) (PP (IN of) (NP (DT this)))) (, ,) (NP (JJ black) (NNS holes)) (VP (VBP are) (ADVP (RBS most) (RB easily)) (VP (VBN detected) (PP (IN by) (S (VP (VBG observing) (NP (PRP$ their) (NNS effects)) (PP (IN on) (NP (NP (JJ other) (NNS bodies)) (PP (IN of) (NP (NN matter))))) (, ,) (PP (IN for) (NP (NP (NN example)) (, ,) (NP (DT a) (NN companion) (NN star))))))))) (. .)))
Because of this, black holes are most easily detected by observing their effects on other bodies of matter, for example, a companion star.
(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))))))))) (. .)))