Mu Aquarii

Mu Aquarii, Latinized from μ Aquarii, is the Bayer designation for a binary star system in the equatorial constellation of Aquarius. It is visible to the naked eye with a combined apparent visual magnitude of 4.7. Based upon parallax measurements, the distance to this system is about 157 ly. It is drifting closer to the Sun with a radial velocity of −9.1 km/s.

This star was tentatively identified as a single-lined spectroscopic binary by Helmut A. Abt in 1961. It has an orbital period of 1566 days and an eccentricity (ovalness) of 0.23. The pair have been resolved by speckle interferometry, showing an angular separation of $1,566 days$. The visible spectrum matches a stellar classification of A3m, with the 'm' suffix indicating that this is an Am, or chemically peculiar star. The primary has an estimated 3.5 times the Sun's radius and is radiating 26 times the luminosity of the Sun from its photosphere at an effective temperature of 6,906 km/s.

This star together with ν Aquarii is Albulaan, derived from an Arabic term al-bulaʽān (ألبولعان) meaning "the two swallowers". This star, along with ε Aqr (Albali) and ν Aqr (Albulaan), were al Bulaʽ (البلع), the Swallower. In Chinese, 女宿 (Nǚ Xiù), meaning Girl (asterism) (or Woman), refers to an asterism consisting of μ Aquarii, ε Aquarii, 4 Aquarii, 5 Aquarii and 3 Aquarii. Consequently, the Chinese name for μ Aquarii itself is 女宿二 (Nǚ Xiù èr, the Second Star of Girl / Woman.)