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In the western parts of the constellation of Andromeda, three stars form a clear downward-pointing triangle. These three stars are Psi, Lambda and Kappa Andromedae, and together they point southward towards a fourth star, faint blue Iota Andromedae. Iota falls close to the Blue Snowball planetary nebula, which lies a little over two degrees to the west.

Imagery provided by Aladin sky atlas

Iota Andromedae lies far from the Solar System at a distance of almost exactly five hundred light years. It is a young dwarf or main sequence star, and a highly luminous one. Though its apparent magnitude as seen from Earth is a modest +4.3, its absolute magnitude is a brilliant -1.7, and the star emits nearly four hundred times as much light energy as the Sun.

The spectral type of this star is B8V, meaning that it has a similar structure to better-known Algol in Perseus, which is also a B8V star. Unlike Algol, Iota Andromedae has no known binary companion, and so where Algol (which is regularly eclipsed by its own companion star) Iota Andromedae shines steadily with a constant level of brightness.


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