Malcolm S. Longair, The Cosmic Century: A History of Astrophysics and Cosmology (Cambridge University Press, 2006) p45 Betelgeuse was found to be 300 times larger than the Sun, with a diameter of 240000000 miles , based on trigonometric calculation from an apparent angular measure of 0.047 of an arcsecond in the Earth sky and the star's 700 light year distance from Earth.