HD 130458 (HR 5520) is a double star[17] in the southern circumpolar constellationofApus. The pair has a combined apparent magnitude of 5.8,[6] making it faintly visible to the naked eye under ideal conditions. Parallax measurements place the system 310-24 light years away[1] and it is receding with a heliocentric radial velocityof31.4 km/s.[7]
The primary is a red giant with a stellar classification of G7 IIIa. It was earlier classified as G8 IIb, indicating a bright giant.The dimmer component has a stellar classification of F9 IV, indicating that it is an F-type subgiant evolving onto the red giant branch. As of 2008 , the pair has an angular separation of 2.167″.[17]
At present the primary has 1.5 times the mass of the Sun[9] but has expanded to 8.9[10] times its girth. It radiates at 55[11] times the luminosity of the Sun from its enlarged photosphere at an effective temperature 5,194 K,[10] which gives it a yellow glow. Currently it spins leisurely with a projected rotational velocityof3.6 km/s,[12] common for giants. HD 130458A is believed to be on the horizontal branch.[4]
As for the secondary component, it has 1.4 times the mass of the Sun and an effective temperatureof6,601 K, giving a yellowish white hue. [9]
