N-COUNT 星系 A galaxy is an extremely large group of stars and planets that extends over many billions of light years.

N-PROPER 银河；银河系 The Galaxy is the extremely large group of stars and planets to which the Earth and the Solar System belong.

N-SING 一群（名人）；（人才）荟萃 If you talk about a galaxy of people from a particular profession, you mean a group of them who are all famous or important.