Why is the sun hotter than Betelgeuse?

Question

Why is the sun hotter than Betelgeuse?

Answer 1

because we are in our prime.  betelgeuse has used up most of its hydrogen and fused it into helium. now its trying to fuse the helium together.  the temp is about half that of the suns but it does produce more energy. The amount of energy radiated per square meter of a star's surface is governed by its temperature, according to the rule:

amt of energy radiated  a  T4 (which assumes the star radiates like a black body).  A star's luminosity is simply the sum total of the energy emitted from each of the square meters of its surface.

Now, Betelgeuse's temperature is one-half the Sun's.  So, from each sq meter, Betelgeuse radiates only (3000/6000)4  =  (1/2)4  =  1/16 as much energy as the Sun.  But, Betelgeuse is a very big star.  It's surface area is much bigger than the Sun's.  So, Betelgeuse's large surface area more than compensates for its low temperature.  Thus, it is much more luminous than the sun.

Answer 2

Do you have objective evidence that it is in fact the case? Otherwise your question is nul and void.

Answer 3

Older Sun = Hotter.

Younger Sun = Colder.

Answer 4

because it's a red giant, and our sun is a yellow star, also smaller.  the smaller and whiter the hotter, the larger and redder the cooler.  also once a star begins to get that red, it gets old, and will eventually die out.

Answer 5

because betelgeuse is older than the sun

EDIT: Betelgeuse is also a Red Giant stage while the Sun, like others have said, is in the prime years of life.