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Calculating the Surface Temperature of A Star





According to Wikipedia, the hypergiant star VY Canis Majoris (VY CMa) in the constellation Canis Major the Big Dog has a radius that's around 1480 solar and a luminosity of 270,000 Suns.


Given this information, we can calculate the surface temperature of the star with the following equation, whereby T = temperature (the unknown), L = luminosity = 270,000 solar, and R = radius = 1480 solar:


T4 = L/R2

T4 = 270,000/14802

T4 = 270,000/2,190,400 = 0.123265

T4 = 0.123265

T = 0.59253 times the Sun's surface temperature in degrees Kelvin


Given that the Sun's surface temperature = 5800 Kelvin, that means the star VY CMa must have a surface temperature of about 3400 degrees Kelvin (0.59253 x 5800 = 3436.674).


Surface Temperature of the star Sirius


What the heck, let's calculate the surface temperature of the star Sirius, given a luminosity of 25 solar and a radius of 1.7 solar:


T4 = L/R2

T4 = 25/1.72

T4 = 25/2.89 = 8.65

T4 = 8.65

T = 1.715 times the Sun's surface temperature in degrees Kelvin


Given that the Sun's surface temperature = 5800 Kelvin, that means the Sirius must have a surface temperature of about 9947 degrees Kelvin (1.715 x 5800 = 9947).

Thus ends this month's astronomy adventure. Hope you enjoyed!


copyright 2013 by Bruce McClure


April 2013 Feature * June 2013 Feature