Yes, thanks Mc Garth! Got me! That's what I get for shooting from the lip! Diameter about 2 billion miles. Betelgeuse has been called the "redhot vacuum" where one could both freeze to death and burn up at the same time. No one really knows how far into space the coronosphere extends beyond what may pass for a surface. However the star is so large that it is the first star ever to have it's disk imaged other than the sun. I remember reading recently that it is in it's last days on the main sequence and could go nova in the next one million years, or tomorrow. Fortunately it would PROBABLY do little or no damage to Earth. They say. However it would shine as bright as a full moon for several years.