Lambda Aquarii


Lambda Aquarii, informally known as Hydor, is the Bayer designation for a star in the equatorial constellation of Aquarius. The apparent visual magnitude of this star is 3.722, which is bright enough to be visible with the naked eye. It is roughly from Earth.

Properties

Lambda Aquarii is a red giant star with a stellar classification of M2.5 III. It is classified as slow irregular variable and pulsation periods of 24.5, 32.0, and 49.5 days have been identified. This star is on the asymptotic giant branch and is generating energy through the nuclear fusion of hydrogen and helium along concentric shells surrounding an inert core of carbon and oxygen.

Naming

Hydor is from Greek Ὕδωρ "water", a name given by Proclus, according to Richard Hinckley Allen. Another Greek name for the star is Ekkhysis, from εκχυσις "outpouring".
In Chinese, 壘壁陣, meaning Line of Ramparts, refers to an asterism consisting of λ Aquarii, κ Capricorni, ε Capricorni, γ Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium. Consequently, λ Aquarii itself is 壘壁陣七

Night viewing

The star is eclipsed by the sun from about 1-4 March. Thus the star can be viewed the whole night, crossing the sky, in early September, in the current epoch. It lies 0.39 degrees south of the ecliptic.