why? GOD has not told us everything He knows. There could be life on another planet and we just don't need to know.
Well, the impression I got from Genesis was that all living things were created in Earth's air, Earth's sea, and on Earth's land.
Anyways, more about the purpose of the stars: Genesis 1:14 And God said, "Let there be lights in the expanse of the heavens to separate the day from the night. And let them be for signs and for seasons, and for days and years, (15) and let them be lights in the expanse of the heavens to give light upon the earth. And it was so." (ESV)