Is Betelgeuse warmer than the sun?
No. While Betelgeuse is larger and brighter than the sun, it actually has a lower surface temperature.
The Sun is a yellow dwarf - Betelgeuse is a red supergiant The Sun has a spectral type of G2V, Betelgeuse is M2 Betelgeuse is about 1,000 times larger than our Sun. Betelgeuse will explode as a supernova our Sun won't. Our Sun has a temperature of about 5,700 Kelvin, Betelgeuse is 3,500 K. Betelgeuse is only a few million years old, the Sun is 4.5 billion years old.
Betelgeuse is much bigger, in size than Rigel - about 12 times. but only just smaller in terms of mass. Betelgeuse has a radius of about 936 times that of our Sun Rigel has a radius of about 78 times that of our Sun Betelgeuse has a mass of 18 times that of our Sun Rigel has a mass of 17 times that of our Sun