Constellations, groups of stars, provide astronomers with a roadmap of the galaxy.
Answer:
groups of stars
Explanation:
Groups of stars is a nonrestrictive <u>appositive phrase</u> that provides additional information about the noun <em>Constellations</em>. It is set off with commas because the information it provides is not necessary for identifying the noun it describes.
the: Every moth Lily goes to the orthodontist to get her braces tightened, afterwards her mom gets her a milkshake because biting into hard food is too painful for her.
