What is the purpose of other planets and solar system according to the bible? Are they just to light up the night? Does the bible even talk about other planets and other solar system with the capability of life or the people who wrote the bible does not know about these solar system because of lack of scientific advancement at that time?
The Bible does recognise the existence of heavenly bodies of some sort, and the fact that they move and come and go during the year:


  Gen 1 14 And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years.


However it calls them lights, which is how they appear from the earth. There is no reference to planets or other such worlds.

There was astronomy in late Biblical times: the Wise Men followed "a star" at the time of Jesus' birth. However the difference between astronomy and what we now call astrology was not clearly defined, and technology had not developed to the extent that Jupiter (the largest and most clearly-featured planet) could be seen to have coloured bands or moons. It was Galileo who first observed its moons, and he got into serious trouble for documenting it and supporting Copernicus.

We may say the Bible is incomplete in describing the heavenly bodies as lights rather than being more specific; but it was written by the writers of the time &mdash; they could not be expected to write down what they could not have understood.