At magnitude 2.91, Sadalsuud, or β Aquarii, is just barely the brightest in the constellation of Aquarius, the Water Bearer. Sadalmelik (α Aqr) and Sadalsuud (β Aqr) have nearly the same apparent brightness. Oddly, the stars also share a name, both referring to "lucky stars." Sadalsuud comes from an Arabic phrase meaning "the luckiest of all of them," and refers not only to Sadalsuud, but to two other fainter stars just to the southeast, one in Capricornus.
Properties
Sadalsuud is a rare star, a relatively warm class G supergiant with a temperature of 5600 K, almost the same as the Sun's. At a distance of 600 light years, it radiates with a luminosity 2200 times solar, from which we infer a size 50 times the Sun's, and a mass of around six times solar. Sadalmelik and Sadalsuud, are similar, but Sadalsuud is brighter than its constellation-mate Sadalmelik only because it is 140 light years closer to us. Both were born together as hot class B stars, similar to those that make up the Pleiades cluster in Taurus.
Evolution
Clearly these stars were not formed in as tight a cluster as the Pleiades, or else they would still be bound together. Instead, they must have been born in a looser association, rather like the stars that make much of Orion today. Their motions over the past tens of millions of years have separated them, but they are still easily in sight of one another. From Sadalsuud, Sadalmelik would be a magnitude zero star. Both seem to be moving more or less perpendicular to the plane of our Galaxy, an odd motion that implies they were somehow kicked away from their birthplace. With similar ages and masses, both are now probably fusing helium into carbon in their deep cores, and will die rather soon as massive white dwarfs.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]