<Li> Betelgeuse is a pulsating star, so its diameter changes with time; </Li> <Li> The star has no definable "edge" as limb darkening causes the optical emissions to vary in color and decrease the farther one extends out from the center; </Li> <Li> Betelgeuse is surrounded by a circumstellar envelope composed of matter ejected from the star--matter which absorbs and emits light--making it difficult to define the photosphere of the star; </Li> <Li> Measurements can be taken at varying wavelengths within the electromagnetic spectrum and the difference in reported diameters can be as much as 30--35%, yet comparing one finding with another is difficult as the star's apparent size differs depending on the wavelength used . Studies have shown that the measured angular diameter is considerably larger at ultraviolet wavelengths, decreases through the visible to a minimum in the near - infrared, and increase again in the mid-infrared spectrum; </Li>

Betelgeuse is about 427 light years from earth. how many kilometers is this