Gamma Aquarii

Gamma Aquarii (γ Aquarii, abbreviated Gamma Aqr, γ Aqr) is a binary star in the constellation of Aquarius. It has an apparent visual magnitude of 3.849, making it one of the brighter members of the constellation. Based upon parallaxmeasurements taken during the Hipparcos mission, this star is located at a distance of approximately 164 light-years (50 parsecs) from the Sun.

Gamma Aquarii is the primary or 'A' component of a double star designated WDS J22217-0123. The secondary or 'B' component is UCAC2 31430071. Gamma Aquarii A's two components are therefore designated WDS J22217-0123 Aa and Ab. Gamma Aquarii is traditionally also called Sadachbia /səˈdækbiə/, a name now formally restricted to γ Aqr Aa.

Gamma Aquarii is a spectroscopic binary with a period of 58.1 days.

It presents as an A-type main sequence star with a stellar classification of A0 V, around two and a half times more massive than the Sun. It is a candidate Lambda Boötis star, suggesting it may have accreted low-metallicity circumstellar gas some time in the past. It is spinning relatively rapidly with a projected rotational velocity of 80 km s−1. This value gives a lower bound on the actual azimuthal velocity along the star's equator. The outer atmosphere of Gamma Aquarii is radiating energy at an effective temperature of 10,500 K, which is nearly double the temperature at the surface of the Sun. This heat is what gives Gamma Aquarii the white-hot glow of an A-type star.