Page:The Music of the Spheres.djvu/186

 in honor of Orion's mother, who was fabled as Euryale, the famous Amazon Queen.

On account of recent discoveries concerning it, Betelgeuse has become one of the most interesting of our stars. When Professor Michelson of the University of Chicago discovered a means of measuring the diameter of stars, he measured Betelgeuse and found it to be of the most enormous size. Indeed, if this huge rose-tinted star were placed in the position of our sun, it would fill the solar system nearly to the planet Mars!

This unique achievement of measuring the diameter of a star made the world sit up in amazement. The measurement was made at the Mount Wilson Observatory with the largest reflecting telescope ever made, a telescope which has an aperture of a little more than 100 inches. A set of mirrors was attached in such a way that for the purpose of measurement the effect of a 20-foot aperture was obtained and Professor Michelson was able to prove that the disk of Betelgeuse has an angular diameter of approximately one twenty-second of a second—which means that if the distance deduced from the best determined parallax of the star is correct, the actual diameter is 230,000,000 miles! But this giant red star is a globe of little density; the dwarf red stars, although about the same mass, are found to be more compact. Hale in "The New Heavens" says that there are good reasons for believing that "the mass of Betelgeuse cannot be more than ten times that of the sun's volume. Therefore its average density must be like that of an attenuated gas in an electric vacuum tube." It is difficult to adjust one's everyday conception of a star to such a sheer and rarefied object. Such a star seems almost too spiritual to exist, and is certainly an amazing thing to picture in the heavens. But Betelgeuse is not a starry spirit, but a full-fledged mammoth star, though it is only recently (in a cosmic sense) that it started on its career.