55 Eridani: A Double Star Floats in a Heavenly River

55 Eridani is a yellow-white double star system in Eridanus, a southern celestial constellation representing a river. It’s best viewed in the winter and early spring. Both stars fall in the 6th magnitude range and look similar, though some observers describe the secondary star as blue. Also, an interesting aspect of the secondary star is that it’s designated as a variable star.

While the stars are physically related, astronomers do not observe orbital motion in this system.

My Observations

55 Erandi is pretty far south in my Seattle skies—low enough that it has been ducking in and out of the cedar trees past my property line. The atmosphere is not too stable as I’m struggling to keep sharp focus on the stars. Perhaps that’s why I cannot tell a difference in color as well. Under these conditions, they both appear yellow-white to me; I’m not seeing blue as some observers indicate. I’d like to return to this one in the future to double-check the color difference between the stars—if any.

Key Stats

Constellation	Eridanus
Best Viewing	Winter / Early Spring
Visual Magnitude	+6.7, +6.8
Absolute Visual Magnitude	-2.41
Distance from Earth	410 ly
Separation	9.2″ | 6010 AU
Orbital Period	Unknown
Milky Way Location	Orion Spur
My Viewing Grade	C

Sources and Notes

Banner shared under the Creative Commons Attribution-Share Alike 4.0 International license. Photo by David Ritter. Details here.

Sketch by Wayne McGraw

AKA: Struve 590, SAO 131443