Suppose a new planet is discovered, which revolves around the sun (i.e. it is a part of our solar system). If its lies between saturn and Jupitar, its time period of revolution would be
We don't know the exact order of all the planets, but Jupiter formed first, with Saturn close behind. Both were finished in less than 3 million years. The inner planets (Mercury, Venus, Earth, Mars) got off to a late start.