Howdy, first post, good to be here. I'm sure it will be a learning experience. My question concerns planetary formation and planet orbits for other stars, specifically the star Vega. I'm having a "disagreement" with someone who claims that Vega's mass, diameter, and density prevents the formation of planets close to the star. I'm having trouble getting this person to define "close", nevertheless I maintain we don't know nearly enough about the physics of planet formation to know this for sure. He also says replace the sun with Vega and Mercury and Venus would not have stable orbits. When I asked the reason he cited the universal law of gravitation and calculated the force of Vega's gravity at Mercury's distance. I find this unconvincing. He also stated force of gravity depends on diameter and density as well as mass, which I dispute. So can anyone clue me in as to what I'm missing here? Thanks!