Alpha Andromedae (a Andromedae, abbreviated Alpha And or a And), officially named Alpheratz, is 97 light-years from the Sun and is the brightest star in the constellation of Andromeda when
Beta Andromedae undergoes its periodical
dimming. Immediately northeast of the
constellation of Pegasus, it is the upper left star of the Great Square of Pegasus
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

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