ASSALAMUALYKUM.
Brother heaven means the entire Universe. The word used for universe is السَّمَاوَاتِ Brother this word is much appropriate than "alkawn." this is because heaven means the universe, the dimensions of the universe and everything. And there might be other secrets which we still don't know. And as I have told you earlier it's Allah's divine choice. Just take for an example, Allah used "Kawkab" to refer to the planets and the word "Najm" to refer to the stars. But the early Muslims were unaware of this fact. They took "kawkab" and "najm" both as stars. I think they also came across this problem what you are facing now.
Just read the article given bellow to know how Allah differentiate between a planet and a star:
http://www.islam-guide.com/bqs/17astronomy.htmIn the same way, Allah used السَّمَاوَاتِ
not الكون to refer to the universe. There has to be a reason behind this as this is Allah's divine choice. Inshallah with the advancement of Science we will come to know about the secret. And brother sky also means the universe. What do you mean by sky? Time, space, planets, stars etc. And our universe is composed of all these things.ALLAH KNOWS THE BEST
Now lets come to the next point.
Quran 41:11) Then He directed Himself to the heaven while it was smoke and said to it and to the earth, "Come [into being], willingly or by compulsion." They said, "We have come willingly."
Brother first, Allah says He directed to the heaven while it had been a smoke . From this it's clear that earth and other components of the Universe were once together. And Allah knows, which portion of the smoke will be earth and which will be other planets and stars. That's why Allah addressed that portion of the smoke as earth, because He knew that portion of the smoke is earth.
"and said to it and to the earth" this proves that they were together and Allah is ordering them to get apart. ALLAH KNOWS THE BEST
The third and last point.
[Quran 20.6] To Him belongs what is in the Heavens and what is on Earth and what is between them and what is under the soil.
Well brother I'm not sure of this verse but still I'll try my best to explain it to you. Brother as I have told you earlier that our universe might have some dimensions or layers as the scientists say. And our earth and all other planets and stars are in the first layer. So I think by this verse Allah wants to say that what ever is between the earth and the layers of the heavens belongs to Him. Brother I'm not sure about this explanation. Do one thing. Post a new thread on this topic, so that the topic is high lighted and brother Osama can help you with this.ALLAH KNOWS THE BEST
May Allah forgive me if I have misinterpreted any of the facts above.
Take Care.