I an trying to calculate the temperature of a hypotethical planet orbiting the CHARA star at a distance of 1 AU. Now I know that the luminosity of Sol is 4x10^26 watts and that Chara's is about 20% more so 4.8x10^26 watts. I found the following equation to calculate it: ( L ) Temp ( in K ) = (--------------) 1/4 (16*pi*S*R^2 ) L = Luminosity of star S = Stefan-Boltzmann constant wich should be 5.67x10^-8 R = radius of planetary orbit in meters where 1 AU is .94x10^12, squared.... Heres where I foud this equation: http://spiff.rit.edu/classes/phys230/lectures/life/life.html I end up with stupid 476510.66 K ... this is supposed to be a planet, not a quasar ! Where am I wrong ? Thanks for help !