Sadalmelik

Sadalmelik lies in the nothern parts of the constellation of Aquarius, towards that constellation's border with Pegasus, and a little to the west of Aquarius' triangular 'Water Jar' asterism. This is one of a group of stars in Aquarius with proper names prefixed Sada(l)-, which ultimately derives from Arabic sa'd, 'luck'. Sadalmelik's full name means 'luck of the king' (and its companions in Aquarius, Sadachbia and Sadalsuud, relate to the 'luck of the tents' and 'luck of lucks' respectively).

Though designated Alpha Aquarii, Sadalmelik is actually very slightly fainter than the Beta star, Sadalsuud. Sadamelik has a visual magnitude of +2.94, while Sadalsuud has a marginally brighter magnitude of +2.89. Though widely separated in space, the two stars in fact have a great deal in common, both belonging to the relatively unusual class of yellow supergiants, and possibly share a common origin.

With an estimated age of some fifty million years, Sadalmelik is an evolved star in the later stages of its life (supergiants exist for far briefer periods than dwarf stars like the Sun). The estimated diameter of this star is more than fifty times that of the Sun, and it emits more than 2,000 times as much energy. Given its spectrum, a star of this kind would be expected to have developed into a pulsating Cepheid variable, but in fact Sadalmelik shows no detectable variability.