I'm not an astronomer, but it seems to me that stars (such as the Sun) are orbited by planets (and some asteroids), while planets (such as Earth, Mars and Jupiter) are orbited by moons. If a celestial body is orbiting a star directly (rather than orbiting a planet), it cannot be called a moon, as far as I know.

What would this word mean?

So you want a general phrase that includes stars and the moon? That is, things that appear in the night sky? . Maybe look up "celestial bodies" these and see if the meaning is close. Might be one of those things that is conveniently said in one language, but not in another.

Does 'lunar' help you? I have poor vocabulary but still want to help.😅