How many planets where a long time ago?

Answer 1

The planets in our solar system formed our of the solar nebular/disk from which the Sun was made (as the Sun formed), some 4,600 million years ago. Therefore there have always been roughly the same number of planets as we have now. However, our solar system could have lost one or more of the original planets that were formed as the planets settled into their current positions. As part of the settling process, orbital resonances can cause planets to interact with each other gravitationally and planets can be ejected from the forming solar system. If this did happen, then we do not how may planets there were originally.