> "What if there was no star in the sky?" does not sound particularly weird

I disagree: The most-charitable scenario I can think of is that someone has context-shifted from regular "stars" to "our sun, Sol, which is technically a star even though we typically consider it separate from the rest."

In other words, it involves a situation where someone is assuming the amount is capped at 1. (Yes, I know binary stars exist.)

Compare:

* "What if there was no star for Earth to orbit?" [Works because =1 is the normal assumption in this context]

* "What if there was no star in the night sky?" [This is weird.]

* "What if there was no constellation?" [This is also weird.]