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)

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Sagittarius
Right ascension	18^h 54^m 10.2^s
Declination	-22° 44' 42"
Apparent magnitude (V)	+4.86
Distance	1850 ± 900 ly (570 ± 270 pc)
Spectral type	K2I+B9V:
Other designations
Ain Alrami, ν¹ Sagittarii, ν¹ Sgr, Nu¹ Sgr, 32 Sagittarii, BD-22 4907, CCDM J18542-2245AB, GC 25918, HD 174974, HIP 92761, HR 7116, IDS 18481-2252 AB, PPM 269055, SAO 187426, WDS J18542-2245AB.

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)

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Sagittarius
Right ascension	18^h 55^m 07.1^s
Declination	-22° 40' 17"
Apparent magnitude (V)	+5.00
Distance	270 ± 21 ly (83 ± 6 pc)
Spectral type	K1Ib/II
Other designations
Ain Alrami, ν² Sagittarii, ν² Sgr, Nu² Sgr, 35 Sagittarii, BD-22 4915, CPD-22  7266, GC 25939, HD 175190, HIP 92845, HR 7120, PPM 269074, SAO 187445

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

1. Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 355. ISBN 0-486-21079-0. Retrieved 2012-09-04.