Struve 3050: A Tight Pair of Stars in Andromeda

Struve 3050 is a binary star in the Andromeda constellation best viewed on autumn nights. It’s a beautiful tight binary of two bright yellow stars nearly equal in brightness.

Observers will most likely find the binary appealing because the stars are fairly bright (+6 magnitude), almost equally bright, and close together at 2.5 arcseconds apart in the sky. They lie only 89 astronomical units apart from each other, and their known orbit period is 717 years.

The primary star is classified as a GO V star, while the secondary star is most likely similar. Some observers note that the stars are both white, while Thomas Lewis marked them down as yellowish in his 1906 collection of Struve stars.¹ My observation (see below) agrees with Lewis’ take on their color.

According to Bob Argyle, the astronomer Christian Mayer first observed this binary star in 1777, the last entry in his double star catalog. Ten years later, on December 13, 1787, William Herschel recorded the pair as H N 58.¹

My Observations

This is a fantastic binary. I’m not sure what draws me to this pair on this cold night. With their light golden color, the stars remind me of sweat bees I once saw on a summer trip to Ohio. Even with the 12mm eyepiece, I’m able to clearly split the two stars.

Key Stats

Constellation	Andromeda
Best Viewing	Autumn
Visual Magnitude	+6.5, +6.7
Separation	2.5″ | 89 AU
Position Angle	343°
Spectral Class	A=G0V
Absolute Visual Magnitude	+4.17
Distance from Earth	94.3 ly
Milky Way Location	Orion Spur
My Viewing Grade	A
Designations	HR 9074, SAO 73656, Struve / STF 3050, HD 224635, HIP 118218

Sources and Notes

Banner illustration was created by the European Southern Observatory (ESO) and is under the Creative Commons Attribution 4.0 International License. Per ESO agreement: Here is the original image on the ESO website.

¹ Argyle, B. (n.d.). October 2016 – double star of the month. Webb Deep-Sky Society: Double Star of the Month: STF 3050. Retrieved December 18, 2022, from https://www.webbdeepsky.com/double-stars/object?object=STF%2B3050

Sketch by Wayne McGraw