A1_Serpentis
11 Serpentis
Star in the constellation Serpens
11 Serpentis is a single[9] star in the constellation of Serpens, located 271 light years away from the Sun. It has the Bayer designation A1 Serpentis,[10] 11 Serpentis is the Flamsteed designation. This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 5.497.[2] It is moving closer to the Earth with a heliocentric radial velocity of −16 km/s.[4]
This is an aging giant star with a stellar classification of K0 III,[3] a star that has used up its core hydrogen and has expanded. It is a red clump giant on the horizontal branch, which indicates it is generating energy through the fusion of helium at its core.[2] 11 Serpentis is 2.75 billion years old with 1.3[6] times the mass of the Sun and has 11[7] times the Sun's radius. It is radiating 50[7] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,767 K.[6]