ASPIDISKE (Iota Carinae). Most stars have no proper name; even some bright ones lack them. How they would envy this one, with not one, but THREE, from each of the classic stellar languages. "Aspidiske" (the Greek Iota star in Carina, the Keel of the ship Argo) comes from the Greek, and means "little shield" (referring to a decoration, not a defensive weapon). As is common, the name does not really belong to the star, but was re-applied from other stars in what are now Puppis and Vela. Alternatives are the Latin "Scutulum" and Arabic "Turais," which mean pretty much the same thing. In the same vein, "Aspidiske" was stolen for "Asmidiske", and used for Xi Puppis. As if that is not enough, the written name "iota" Car is often confused with the Roman-letter "l" ("el") Car (a very different and cooler Cepheid variable), which makes a mess of listed stellar properties. This bright, second magnitude (2.25) star is perhaps best known popularly as part of the "False Cross" (which includes Avior, Kappa Velorum, and Delta Vel), a figure that is sometimes mistaken for the genuine article, Crux, the Southern Cross. Physically, Aspidiske is impressive, a rather rare white class A (A8) supergiant (albeit on the low side of the class) with a large measured distance of 690 light years (good to within about 10 percent) and a temperature of 7400 Kelvin. It shines with the light of 4900 Suns, from which (with the temperature) we calculate a radius of 43 times solar. A projected equatorial rotation speed of 10 kilometers per second gives a long rotation period of under 215 days. Rather oddly, the star radiates some X- rays, which implies magnetic activity. The metal content is argued, and ranges from 0.4 times that of the Sun to roughly solar (the star, as is common for southern ones, understudied). Luminosity, temperature, and stellar structure theory lead to a good-sized mass of 7 times that of the Sun and an age of about 40 million years. Aspidiske started life as a hot class B hydrogen- fusing dwarf, and is now mostly likely swelling and cooling with a dead helium core, though it is marginally possible that it has already fired its helium and is shrinking and brightening. Clearly under the limit required for supernovae, Aspidiske will expire quietly as a white dwarf of about a solar mass (rather on the high side) quite similar to Sirius B, though without a companion to watch it all happen.
Written by Jim Kaler. Return to STARS.