Why was the word "kawkab" (planet) used instead of "najm" (star) in Surat Yusuf in His, the Almighty's, saying: "Indeed, I saw eleven kawkaban (planets)"?

The terms "planet" (kawkab) and "star" (najm) are synonymous. This is supported by what Al-Hakim narrated from Jabir, that a Jew asked the Prophet, peace and blessings be upon him, about the "stars" (nujūm) that Yusuf (Joseph), peace be upon him, saw. As for the wisdom behind specifically using the word "kawakib" (planets/celestial bodies) in the expression, we do not know it. Perhaps it is due to their lightness or their harmony with the context.