Mu_Draconis
Mu Draconis
Star in the constellation Draco
Mu Draconis (μ Draconis, abbreviated Mu Dra, μ Dra) is a multiple star system near the head of the constellation of Draco. With a combined magnitude of 4.92,[2] it is visible to the naked eye. Based on parallax estimates by the Hipparcos spacecraft, it is located approximately 89 light-years from the Sun.[1]
The system consists of a single primary star (designated Mu Draconis A, officially named Alrakis /ælˈreɪkɪs/ from the traditional name of the system),[8][9] a secondary binary pair (Mu Draconis B) and a further single star (C). B's two components are designated Mu Draconis Ba and Bb.
Mu Draconis A and Ba are nearly identical F-type main-sequence stars, with masses of 1.35 M☉ and 1.30 M☉, respectively.[7] Both have the spectral class of F5V, and have similar apparent magnitude, at 5.66 and 5.69, respectively.[3] The secondary, Mu Draconis B, has a drifting radial velocity, and is itself a spectroscopic binary with an orbital period of 2,270 days.[10] The distance between both stars is 2 arcseconds, so a telescope with a diameter of at least 6 centimetres is necessary to see them separate. The smaller component, Mu Draconis Bb, has a mass of 0.2 M☉. Mu Draconis C is a 14th magnitude common-proper-motion companion 13.2" away from the bright pair, with a mass of 0.29 M☉.[7]