Beta Aquarii

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β Aquarii, known under its common name designation Sadalsuud, is the brightest star in the constellation Aquarius.

Naming and mythology

Like its near twin α Aquarii, this star's name contains the Arabic for "luck", its full meaning translating roughly as "Luckiest of the lucky". It was so named because the time of year when the sun passes nearest to Sadalsuud coincides with the end of winter.[1]

Observational attributes

Sadalsuud's apparent magnitude is +2.91 making it slightly brighter than α Aqr. The star can be found at the coordinates R.A. 21h 31m 33.5s and Dec. -5° 34ˈ 16ˈˈ. The distance from the Earth to this star is roughly 600 light years which is fairly consistent with the observed parallax of 0.006ˈˈ[2]

β Aquarii can be used as a starting point in locating the globular cluster Messier 2 which lies about 5° to the north.

Physical characteristics

Similar in nature to its near twin in Aquarius, Sadalmelik, β Aquarii is also classed as a yellow supergiant. Its spectral class is G0Ib indicating a surface temperature of some 5.600 Kelvin. From its total luminosity of about 2.200 solar luminosities a mass of about 6 times solar and a diameter of some 50 times that of the sun can de deduced.[3]

Two optical companion stars are associated with Sadalsuud, both of 11th magnitude.[4]


  1. Star Names: Their Lore and Meaning, Richard H. Allen, Dover Publications 1963 (revised edition)
  2. Bright Star Catalog 5th revised edition, 1991
  3. Jim Kaler's Stars, online at
  4. The Washington Visual Double Star Catalog, 1996