Beta Aquarii, a Luminous Yellow Supergiant

Sadalsuud is Beta Aquarii, and it is the brightest star of Aquarius, a rare and remarkable object: a yellow supergiant of spectral type G0 lying at roughly 540 light years, a star of the same colour as the Sun but vastly larger and thousands of times more luminous, its modest appearance in the sky entirely the effect of its great distance. Its name, from the Arabic sa'd al-su'ud, means the luck of lucks or the luckiest of the lucky, one of a series of fortunate sa'd names given to stars of this region, the House of the Fortunate.

Sadalsuud belongs to a small cluster of Aquarius and Capricornus stars carrying sa'd, fortunate, names, Sadalmelik, Sadachbia and others among them, part of what Arabic tradition called the "asterisms of good fortune" filling this stretch of the ecliptic; the cluster of favourable names across an otherwise dim and unremarkable region of sky is thought to reflect this part of the year's association with reliable seasonal rains in the pre-Islamic Arabian calendar rather than anything about the stars' appearance. Sadalsuud's great luminosity despite its modest apparent brightness is explained entirely by distance, the same effect that makes Deneb in Cygnus appear fainter than much closer, intrinsically far dimmer stars.