壁宿二（Alpha And / α And / α Andromedae）在英文的固有名称是 Alpheratz和Sirrah（与Sirah的拼法相通），是在仙女座中最亮的一颗恒星，位置紧邻在飞马座的东北部，是构成飞马四边形的恒星之一。做为一颗与飞马座相连接的恒星，它也曾经被称为飞马座δ，但这个名称现在已经不再使用了。另一颗有双重名称的恒星是金牛座β 。壁宿二与地球相距97光年，虽然以裸眼观看是一颗视星等2.06等的单独恒星，实际上他是一对联星，由轨道距离很近的两颗恒星组成。两颗恒星中较亮的一颗是化学组成很不寻常的汞-锰星，它的大气层中包含异常高浓度的汞、锰和其他元素，包括镓和氙，是已知的汞-锰星中最亮的一颗。

Alpha Andromedae (Alpha And, α And, α Andromedae), which has the traditional names Alpheratz (or Alpherat from the Arabic word الفرس) and Sirrah (or Sirah), is the brightest star in the constellation of Andromeda. Located immediately northeast of the constellation of Pegasus, it is the northeastern star of the Great Square of Pegasus. Ptolemy considered Alpha Andromedae to be shared by Pegasus, and Bayer assigned it a designation in both constellations: Alpha Andromedae (α And) and Delta Pegasi (δ Peg). When the modern constellation boundaries were fixed in 1930, the latter designation dropped from use.