Betelgeuse is a red supergiant star in constellation Orion. Its the one of the largest red supergiant ever known. This star has at least 20 solar mass with diameter of Jupiter's orbit with make about 1 billion miles in diameter across. It is one of the first star to be seen as a disk in very large telescope. This star is very old in age before exploding into supernova and becoming a neutron star. It originally began as a O main sequence giant star at least 30 solar mass and have a diameter of 20 million miles. Now it has temperature of only 5000 F* and the density of that less than best vacuum made on earth. The red color of this star comes from the impurity of titanium dioxide in the star's atmosphere that lower the temperature of outer layers.