NASHIRA (Gamma Capricorni). Though Capricornus is a relatively faint constellation, its stars are arranged to make a rather prominent figure. Across the top are four reasonably bright stars that claimed Bayer's first four Greek letters, Alpha (Algedi) through Delta (Deneb Algedi). Bayer seems to have used position more than brightness, as Delta is easily the brightest of them. Nashira, the Gamma star, at bright fourth magnitude (3.68), comes in fourth. The meaning of the Arabic name is unknown. At one time it was applied to both the Gamma and Delta stars (which appear to lie close together in the sky), but is now applied to Gamma alone. For a star so reasonably bright, Nashira has a rather checkered classification history. It has been traditionally listed as a class F (F0) star whose evolutionary status is uncertain, and was by default considered a main sequence dwarf, one that like the Sun quietly fuses hydrogen into helium in its deep core. However better observations now suggest a white class A (A7) star. That and the star's distance of 139 light years allows a calculation of luminosity, showing it radiate 47 times more energy than the Sun. The combination of the star's 7950 Kelvin temperature and the luminosity reveal a mass of 2.5 times that of the Sun and show Nashira most likely to be a nascent giant star, one that has stopped its internal hydrogen fusion or is very close to doing so. Nashira seems to be rotating slowly, only 30 kilometers per second (or more) at the equator. That is 15 times greater than the solar rotation speed, but still small compared to the common much more rapid speeds of class A (and hotter) stars. Relatively slow rotation means less atmospheric stirring and a possible separation of elements (some kinds of atoms falling inward, others lofted outward), and indeed Nashira seems to be classified as "metallic- line star," though there has been no in-depth study of it. Few of the "facts" about the star are secure. If nothing else, Nashira shows that we still have a great deal to learn about even modestly bright stars that are prominent parts of their constellations.
Written by Jim Kaler. Return to STARS.