Of multiple stars the most famous is 0 Orionis, situated near the densest part of the great Orion nebula.
Thus it is found that Procyon gives about three times as much light as the sun in proportion to its mass, Sirius about sixteen times, and Orionis more than ten thousand times.
The Orion stars have the highest temperature of all and have admittedly the greatest surfaceluminosity, but the extreme brilliancy of i Orionis in proportion to its mass must be mainly due to a small density.
In 1920 he was able to demonstrate by means of light-interference that the diameter of Alpha Orionis was 260,000,000 miles.
A Orionis, or Betelgeuse, is a bright, yellowish-red star of varying magnitude (0.5 to 1.4, generally 0.9).