56 Andromedae: A Golden Orange Treat

56 Andromedae is a double star in the Andromeda constellation best viewed on autumn nights.

This optical pair of stars, meaning they are not physically related, is separated by 202 arcminutes. That’s pretty wide for double stars. For comparison, a full moon is 1,900 arcseconds across.

Since 56 Andromedae’s stars are bright and wide from each other, they make for an attractive target with binoculars and telescopes from suburban locations. The primary star is classified as a giant KO star, while the secondary star is a big MO star.

This system makes for a good lesson on optical illusions because our eyes perceive two stars that appear close to each other with nearly the same brightness. In reality, the primary star is around 360 light-years away from us, while the secondary star is three times farther away at 1,200 light-years!¹

Be sure to stop by the NGC 752 if you are looking at 56 Andromedae as the open cluster is within a degree away.

My Observations

On this freezing late autumn night, I’m enjoying several double stars, including this pretty optical double called 56 Andromedae. The primary is gold in color, while the secondary appears the same brightness but is playing games with my eyes. At first glance, it appears pinkish, and then again, perhaps it is a light orange.

Key Stats

Constellation	Andromeda
Best Viewing	Autumn
Visual Magnitude	+5.7, +6.0
Separation	202.5″
Spectral Class	A=KO, B=MO
Absolute Visual Magnitude	+.76
Distance from Earth	316 ly
Milky Way Location	Orion Spur
My Viewing Grade	B+
Designations	56 And, SAO 55107, HD 11749, STFA 4, HR 557

Sources and Notes

¹ Argyle, Bob. “November 2015 – Double Star of the Month.” Webb Deep-Sky Society: Double Star of the Month: 56 And, https://www.webbdeepsky.com/double-stars/object?object=56%2BAnd.

Sketch by Wayne McGraw