Struve 1677: A Close Pair of Stars Near Porrima in Virgo

Struve 1677 (STF 1677) is a double star in the constellation Virgo, best viewed on spring nights.

I just realized something as I write this observation. Since starting this site three years ago, my observations in Virgo have focused on its rich galaxy collection. The only double star I’ve observed so far in Virgo is the notable Porrima. Thus, nearby Struve 1677 is the second of hopefully many more doubles. On a related note, I like how John Nanson of Star Splitters puts STF 1677 into a group called “Porrima’s Pals!”

STF 1677’s two stars are close together, but you can comfortably split them since they are 16 arc seconds apart. The primary star is a yellow-white giant classified as an A7 (III) star, and it shines at a magnitude of +7.3. Meanwhile, the nearby and fainter companion shines at a magnitude of +8.1.¹

The astronomer William Herschel was the first person to record this double star. He penned his observation on February 17, 1782.¹

My Observations

Other observers have seen the primary star as white, and the secondary star as either gray or slightly yellow. I find my observations differ slightly. The primary, which is the bottom star through my eyepiece and on the sketch, appears white with a very slight touch of yellow. The secondary looks gray to me, though it may be just a dim white. Since this is a close, but fairly easy double to separate, backyard astronomers should definitely check it out when they go looking for galaxies and Porrima in this region.

Key Stats

Constellation	Virgo
Best Viewing	Spring
Visual Magnitude	+7.3, +8.1
Separation	16″
Position Angle	348°
Spectral Class	Primary=A7(III)
Absolute Visual Magnitude	+0.16
Distance from Earth	188 ly
Milky Way Location	Orion Spur
My Viewing Grade	B+
Designations	SAO 138952, HIP 62234

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 The herschel 500 double star list. (n.d.). Retrieved May 6, 2023, from https://www.handprint.com/ASTRO/Herschel500.html

Sketch by Wayne McGraw