(S (S (BASENP (NNS Astronomers)) (VP (VBP have) (VP (VBN discovered) (NP (BASENP (DT an) (JJ extrasolar) (NN planet)) (SBAR (WHNP (WDT that)) (S (VP (MD may) (VP (ADVP (RB eventually)) (VP (VB collide) (PP (IN into) (BASENP (PRPD its) (NN sun)))))))))))) (PERIOD .))