GOMEISA (Beta Canis Minoris). Carrying seemingly one of the odder star names, Gomeisa (hard "G", the "ei" said as long "a" or short "i") comes from an Arabic term that means "the little bleary-eyed one." Though the Beta star of Canis Minor, the smaller of Orion's two hunting dogs, the name has no canine significance. The term was instead transferred from Canis Minor's Procyon, which now carries a Greek name, and originally referred to the brighter star as a weeping sister left behind when Sirius and Canopus ran to the south to save their lives. Star names are nothing if not convoluted, even inscrutable. At mid-third magnitude (2.90), the star is notable more for its proximity to bright Procyon. Yet it is by far the more glorious star, rendered apparently fainter only by its larger distance of 170 light years, 15 times Procyon's distance. Gomeisa is a blue-white class B (B8) star with a temperature of 11,500 Kelvin, just a bit warmer than Orion's Rigel. Unlike Rigel, Gomeisa is a main-sequence "dwarf" that, like the Sun, is fusing hydrogen into helium in its core. Like the Sun it is also single, showing no evidence for any companion. However, with a mass over three times the Sun's, Gomeisa radiates far more furiously, shining with 250 solar luminosities, the star directly measured to be four times larger than the Sun. Like most class B stars (which range between about 10,000 and 30,000 Kelvin), Gomeisa is a fast rotator, spinning at its equator with a speed of at least 250 kilometers per second, 125 times the solar rotation speed, giving the star a rotation period of only about one day. Since we may be looking more at the star's pole than at its equator, it may be spinning much faster, and indeed is rotating so quickly that it is surrounded by a disk of matter that emits radiation, rendering Gomeisa a "B-emission" star rather like Gamma Cassiopeiae and Alcyone. Like these two, Gomeisa is distinguished by having the size of its disk directly measured, the disk's diameter almost four times larger than the star. Like quite a number of hot stars (including Adhara, Nunki, and many others), Gomeisa is also surrounded by a thin cloud of dusty interstellar gas that it helps to heat. (Thanks to Jason Pero, who helped research this star.)
Written by Jim Kaler. Return to STARS.