ALFECCA MERIDIANA (Alpha Coronae Australis). South of Sagittarius lies one of the sky's more charming figures, Corona Australis, the Southern Crown. The counterpart of Ariadne's Corona Borealis (the Northern Crown), the Southern version may represent the crown of Sagittarius itself. While the Northern Crown's "lucida," its brightest star, is at second magnitude quite prominent, the Southern Crown's lucidae (of which there are two) are not, the Alpha and Beta stars tied at mid-fourth magnitude (4.11). Alpha at least boasts a name, one not so much its own but one that reflects the Northern Crown's prominence. The brightest star in Corona Borealis is named "Alphecca," from Arabic for "break," the name coming from the half or broken circlet of stars that makes the Crown's figure. Probably in response, the Alpha star of Corona Australis is known as Alfecca (note the curious spelling change) Meridiana. The name at first makes no sense, as "Meridiana," from Latin, refers to noon, when the star would hardly be visible. However, when a resident of the northern hemisphere looks to the Sun at noon, he or she looks to the south, leading to an alternative definition of "meridiana" as "southern," Alfecca Meridiana thus referring directly to Corona Australis. Other than the problem of the name, the star is rather ordinary, one of vast numbers of warm class A hydrogen-fusing dwarfs that dot the sky and make so much of our familiar constellations. At a distance of 130 light years, the star shines 31 times more brightly than does the Sun, from a surface with a temperature of 9100 Kelvin. There is some argument as to the spectral class, some authorities moving it to hotter class A1 or even A0 (though that is out of line with temperature). A decidedly single star (so far as anyone knows), Alfecca Meridiana is a fast rotator, spinning at least at 180 kilometers per second at its equator, 90 times faster than the Sun. With a radius 2.3 times solar, it makes a full rotation in under 18 hours (the Sun taking 25 days). More interesting, Alfecca Meridiana is a "Vega" candidate, a star that like Vega radiates excess infrared radiation that seems to come from a surrounding disk of cool dust, suggestive of some kind of surrounding planetary system (for which there is no other evidence). With a mass around 2.3 times solar, Alfecca Meridiana is about half-way through its hydrogen-fusing main-sequence lifetime, and will eventually turn into a relatively heavy white dwarf, just like all the stars of its class. Thanks to David Bright for advice on the star's name.
Written by Jim Kaler. Return to STARS.