Salam Yahya
53:1
By the star when it goes down,
This verse is followed by
53:2
Not has strayed your companion and not has he erred,
The stars in 53:1 is mentioned to give an idea about the sacredness or truthfulness of the next claim that was being made about the Prophet being on the correct path.
There are many cultures where people make oaths by mentioning other things like the head. From my culture, it is fairly common to make oaths by saying that I promise on my parents or children, by which we mean that I am not lying because in my culture it is believed that lying when u take an oath by naming ur dear ones, u risk putting a curse on them and urself. It is considered a big sign of a person's truthfullness in my culture.
Maybe at the Prophet's time, the Arabs held stars and planets with esteem not unlike how ppl in my culture treat dear ones. Or maybe the Arabs were at awe with stars and planet, so such an oath was the best way to convince them. This maybe has nothing to do with science, or how stars do not fall, meteors do.
Then again, we are not told whether stars are created somewhere else above the sky and then dropped in their assigned position in the galaxy or not. We do not know. Maybe stars and planets are not made in the positions that they occupy currently in the sky.
Our ultimate destiny is heaven/or hell, but we are not currently being tested in heaven or hell. We are also told that our ancestors were asked to go down. Maybe, somethings in creation ( living and non- living), like us , are created in one place, tested in another and ultimately end up in a completely different resting place.
We always have to keep in mind that the primary audience of the Quran was 7th century Arabs. They did not have our understanding of science nor our culture. Revealing scientific knowledge which they couldn't have understood on any level, would have served no purpose. It would have confused them more and make them more doubtful about the veracity of the Quran. God is the ultimate judge, He has chosen words very carefully in the Quran. Also present day Arabs do not share the same understanding with their 7th century ancestors regarding a lot of religous and cultural aspects. Time changes even the culture of a country and its people.