Answer: originator of trigonometry.
Step-by-step explanation:
An appositive phrase is a noun phrase, usually directly after the noun that adds information to the noun in order to make the sentence more clearer and enable the reader have a more vivid description of the noun.
The appositive phrase in this sentence ---Hipparchus originator of trigonometry in the 2nd century BCE celestial bodies is originator of trigonometry