I am trying to determine if I am on the right track by using the Stefan-Boltzmann Law to calculate the distance a point in space must be to have a given temperature. For example, the snow line (a.k.a. frost line, ice line) of a star is when the temperature reaches 160°K ± 10°K. Using the Stefan-Boltzmann Law : Where: TE = The temperature of the black body object, in Kelvins (160°K in this case) TS = The surface temperature of the star, in Kelvins rS = The radius of the star, in meters a0 = The distance the black body object is from the star, in meters Using Sol's data as an example, a black body object would have a temperature of 160°K at 3.04 AU. Yet, according to a paper published on May 9, 2003, the frost line for the Sol system should be ~5 AU. Remote Infrared Observations of Parent Volatiles in Comets: A Window on the Early Solar System Which leads me to believe that my approach is incorrect since it does not match our observations. If someone can set me right, it would be greatly appreciated.