 The surface temperature of a main sequence star is determined by the rate of energy production of its core and by its radius , and is often estimated from the star 's color index . The temperature is normally given in terms of an effective temperature , which is the temperature of an idealized black body that radiates its energy at the same luminosity per surface area as the star . Note that the effective temperature is only a representative of the surface , as the temperature increases toward the core . The temperature in the core region of a star is several million kelvins . 
 The surface temperature of a main sequence star is determined by the rate of energy production of its core and by its radius , and is often estimated from the star <a href='null_genetive' title='1'><mark>'s</mark></a>color index . The temperature is normally given in terms of an effective temperature , which <a href='drop_aux' title='2'><mark>is</mark></a>the temperature of an idealized black body <a href='null_relcl' title='3'><mark>that</mark></a><a href='uninflect' title='4'><mark>radiates</mark></a> its energy at the same luminosity per surface area as the star . Note that the effective temperature is only a representative of the surface , as the temperature <a href='uninflect' title='5'><mark>increases</mark></a> toward the core . The temperature in the core region of a star <a href='drop_aux' title='6'><mark>is</mark></a>several million kelvins . 
The surface temperature of a main sequence star is determined by the rate of energy production of its core and by its radius , and is often estimated from da star  color index . The temperature is normally given in terms of an effective temperature , which the temperature of an idealized black body radiate its energy at the same luminosity per surface area as the star . Note that the effective temperature is only a representative of the surface , as the temperature increase toward the core . Tdatemperature in the core region of a star several million kelvins .