Nu Sagittarii

The Bayer designation Nu Sagittarii (Nu Sgr, ν Sagittarii, ν Sgr) is shared by two star systems, ν¹ Sagittarii and ν² Sagittarii, in the constellation Sagittarius. The two stars are separated by 0.23° in the sky. Nu Sagittarii also has the traditional name Ain al Rami.

Nu Sagittarii is often cited as one of the earliest identified double stars. In the Almagest, Ptolemy describes the star as "nebulous and double", referring to the double nature of the star, as well as the nearby globular cluster NGC 6717.

ν¹ Sagittarii

Nu¹ Sagittarii

Location of ν¹ Sagittarii (circled)

Nu¹ Sagittarii (Nu¹ Sgr, ν¹ Sagittarii, ν¹ Sgr) is a triple star system lying approximately 1850 light years from Earth. The primary component, Nu¹ Sagittarii A, is a spectral type K1 bright giant which has an apparent magnitude of +4.86. It is orbited by two magnitude +10.8 companions: Nu¹ Sagittarii B at a distance of 2.5 arcseconds from the primary, and Nu¹ Sagittarii C at a distance of 28.2 arcseconds.

ν² Sagittarii

Nu² Sagittarii

Location of ν² Sagittarii (circled)

Nu² Sagittarii (Nu² Sgr, ν² Sagittarii, ν² Sgr) is a spectral type K1 supergiant which has an apparent magnitude of +5.00. It is approximately 270 light years from Earth.

Name and etymology

• The name Ain al Rami is from the Arabic عين الرامي ^cain ar-rāmī meaning eye of the archer.^[1]
• Both of ν stars, together with τ Sgr, ψ Sgr, ω Sgr, 60 Sgr and ζ Sgr were Al Udḥiyy, the Ostrich's Nest.^[1]

References

• On-Line copy of the Almagest's star catalog