They are both generic, but because the context of most texts we write is here on Earth, 'sun' and 'moon' tend to be used as proper names would, but without capi

They are both generic, but because the context of most texts we write is here on Earth, 'sun' and 'moon' tend to be used as proper names would, but without capitalisation. That these are essentially generic nouns can show up more clearly in astronomical texts and of course in literature (science fiction).