Alpha Andromedae

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.

It is located 97 light-years from Earth. Although it appears to the naked eye as a single star, with overall apparent visual magnitude +2.06, it is actually a binary system composed of two stars in close orbit. The chemical composition of the brighter of the two stars is unusual as it is a mercury-manganese star whose atmosphere contains abnormally high levels of mercury, manganese, and other elements, including gallium and xenon. It is the brightest mercury-manganese star known.