It is possible I’ve made a completely imaginary link, but “no star in the sky” sounds slightly odd but in a poetic way. In particular “no star” seems pretty close to “not a star.” I mean, zero stars is technically zero stars.

But if someone says “There was no star in the sky,” I parse that as something like: An astonishingly dark night, I searched the sky quite carefully and found not even one star.

Meanwhile I parse “no stars in the sky” as: a very dark night, I didn’t see any stars.

Of course really, it is always a matter of degree technically, right? The stars are always there. They are just sometimes attenuated to the point where your eye doesn’t detect them.

> "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.]

This example does sound wrong to a native English speaker. It contains a subjunctive mood construct and the correct version would be:

"What if there were no stars in the sky?"

It sounds natural to me only if you're expecting exactly one star. For example:

The Three Wise Men are back. But this time, there's no star in the sky to guide them.