The name of the star is Wormwood. A third of the waters turned bitter like wormwood oil, and many people died from the bitter waters.
Textus Receptus (TR) - Revelation 8:11 >Καὶ τὸ ὄνομα τοῦ ἀστέρος λέγεται Ἄψινθος· καὶ γίνεται τὸ τρίτον τῶν ὑδάτων εἰς ἄψινθον, καὶ πολλοὶ ἀνθρώπων ἀπέθανον ἐκ τῶν ὑδάτων, ὅτι ἐπικράνθησαν.