What's the noun for galaxies? Here's the word you're looking for.
(now rare) The Milky Way; the apparent band of concentrated stars which appears in the night sky over earth. [from 14th c.]
(astronomy) Any of the collections of many millions or billions of stars, galactic dust, black holes, etc. existing as independent and coherent systems, of which there are billions in the known universe. [from 19th c.]