To begin with, I am an enthusiastic but very amateur physicist. I am working on my knowledge by taking online open courseware, buying textbooks and doing all the questions. I recently bought Astrophysics of Planet Formation which is no doubt out of my league but I like to pick at it from time to time. In the first page it talks about the maximum mass of a planet being at the deuterium burning threshold. I decided I wanted to do a simple calculation to see if I could get the core temperature of a “star” like this. I set the hydrostatic equilibrium equation to the ideal gas law and solved for the temperature. I was looking for a temperature of 10^6 K. Is this approximation too simplistic? I am within an order of magnitude in my answer if I approximate the radius to be the size of the sun.