Asked by: David Kelly, Manchester
If Jupiter had carried on growing, it would eventually have become a star. If this star was a barely luminous ‘brown dwarf’, it would have only a minor effect on planetary orbits.
But if it had become a more massive star, it would probably have prevented planets from forming in stable orbits, and in any case would have greatly increased the amount of radiation their surfaces receive. So the development of life in our Solar System would have been far less likely.