Nu Boötis

The Bayer designation Nu Boötis (ν Boo / ν Boötis) is shared by two star systems, in the constellation Boötes:

• ν¹ Boötis
• ν² Boötis

Location of the ν Boötis pair (circled)

ν Boötis in optical light. ν² is the blue-white star to the left. ν¹ is the orange star to the right.

They are separated by 0.175° on the sky.^[1] They have almost identical visual magnitudes, but contrasting colours: ν¹ is a yellow giant star, while ν² is a close binary with two white main sequence stars.

Both stars were members of asterism 七公 (Qī Gōng), Seven Excellencies, Heavenly Market enclosure.^[2]

Ptolemy considered Nu Boötis to be shared by Hercules, and Bayer assigned it a designation in both constellations: Nu Boötis (ν Boo) and Psi Herculis (ψ Her). When the modern constellation boundaries were fixed in 1930, the latter designation dropped from use.^[3]