Recently, I've been using a site called "The WorldSmith 3.03" in order to calculate some of my planet's physical characteristics:
Now, when it comes to the planet's gravity there is something that confuses me. There are two values that I need to fill in, in order to get my planet's surface gravity: Mass & CMF (Core Mass Fraction). I was always under the impression that a planet's gravity is only determined by its mass, so if I make my planet have a mass of 2 M Earth (twice that of Earth) then the gravity of the planet should also be 2 g. However, when i put in a value for CMF (39% for instance) then the calculations put my world's gravity at 1.408 g. Why is that?
Let me clarify, I have no problem with these values, I think they work just fine for my world. I just want to make sure if they are true and if yes then I want to understand how exactly does the value of CMF effect a planet's surface gravity?