# 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:

## T^{4} = L/R^{2}

## T^{4} = 270,000/1480^{2}

## T^{4} = 270,000/2,190,400 = 0.123265

## T^{4} = 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:

## T^{4} = L/R^{2}

## T^{4} = 25/1.7^{2}

## T^{4} = 25/2.89 = 8.65

## T^{4} = 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