The Colorful Double Star Almaak in Andromeda

Almaak, a double star in the constellation Andromeda (credit: Mt. Lemmon Observatory)

Almaak, a double star in the constellation Andromeda (credit: Mt. Lemmon Observatory)

High in the northeast sky, Almaak, the third-brightest star in the constellation Andromeda, is one of the most beautiful double stars in the sky. It’s a snap to find and reveals its full splendor in even the smallest of telescopes.

Almaak (sometimes spelled Almach) is a 2nd magnitude star, bright enough to see even in the city. It lies between the Great Square of Pegasus and the bright stars of the constellation Perseus.  To find Almaak, also called γ (gamma) Andromedae, start at the northern corner of the Great Square at the star Alpheratz, then move to Mirach, then to Almaak.  If you continue the line you’ll reach Mirphak in Perseus.

An image showing the position of Almaak (gamma Andromedae).  Click to enlarge.

An image showing the position of Almaak or Almach (gamma Andromedae).  Click to enlarge.

Almaak is well overhead for observers in the northern hemisphere in the waning months of the year at about 9 p.m. It’s also visible from the populated parts of the southern hemisphere about 10-15º above the northern horizon at 8-9 p.m. local time in November and December.

You will need a telescope to resolve this star.  The pair is about 10” (arc seconds) apart, so try 50-75x and work your way to higher magnification. Even the smallest scope will do.

Most double stars don’t display much color, especially for novice observers. But Almaak is different.  Like Albireo in the constellation Cygnus, the two visible component stars of Almaak show a splendid color contrast. The brighter is a K-type giant star that shines golden yellow, while its companion is a hot blue main-sequence star. Depending on your optics, your eyes, and your seeing conditions, you may perceive different colors.  The 19th-century amateur Admiral William Henry Smyth saw the pair as orange and emerald-green.  Have a look for yourself… what do you see?

While you won’t see this in any telescope, the fainter blue star, called gamma-2 Andromedae, is itself a triple star system.  So there are four stars here altogether.  The gamma Andromedae system is about 350 light years from Earth.

Almaak takes its name from the Arabic for a “desert lynx”, a type middle-eastern wildcat, which plays no part in the Greek legend of Andromeda and Perseus.

 

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