Hi all, I have just joined this forum to see if anyone here can help me out. First off, I am creating fictional planets that orbit fictional stars. I have given all of my planets a diameter and a distance from their sun. From this, I have managed to calculate their orbital periods and orbital speeds using Kepler's third law. So using this criteria is it possible to calculate the mass of the planet? Also, if possible, I would like to calculate their gravity as well. Thanks in advance.