e Tauri (Struve 452): A Blue Primary with a Dim Companion in Taurus

e Tauri is a double star featuring a bright primary light blue star with a dimmer secondary star in the constellation Taurus, the Bull. Taurus is most prominent during winter evenings in the Northern Hemisphere. The next time you’re out under winter skies, be sure to visit this nice pair first recorded by William Herschel on September 7, 1782.¹

The magnitude +5 primary star shines blue and is classified as stellar type B3V. The dimmer viewable secondary star, at magnitude +9.8, appears white in color and is classified as a yellow-white F5V star. The two stars are separated by 9.2 arcseconds and lie 139 light years away from Earth. According to the latest findings, the nature of this double is uncertain in that we don’t know if the two stars are physically related.

My Observations

e Tauri’s bright primary star appears light blue, while the nearby dimmer secondary appears a dull white. Of note, I few minutes ago, I sketched another winter double called 14 Aurigae. These two star systems have some similarities that may be worth going back to compare.

Key Stats

Constellation	Taurus
Best Viewing	Winter
Visual Magnitude	+5.0 | +9.8
Separation	9.2″
Position Angle	60°
Spectral Class	B3V & F5V
Milky Way Location	Orion Spur
My Viewing Grade	B
Designations	30 Tau, SAO 93611, HD 23792, HR 1174, STF 452

Sources and Notes

Banner adapted from an illustration created by Pablo Budassi. The illustration is licensed under the Creative Commons Attribution-Share Alike 4.0 International license. Full details here.

¹ William Herschel’s double star catalog. (n.d.). https://www.handprint.com/ASTRO/Herschel_All.html

Sketch by Wayne McGraw