Sigma Sagittarii

Sigma Sagittarii
Location of σ Sagittarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 55m 15.92650s[1][2]
Declination –26° 17′ 48.2068″[1][2]
Apparent magnitude (V) 2.05[3]
Characteristics
Spectral type B2.5 V[4]
U−B color index –0.761[5]
B−V color index –0.204[5]
Astrometry
Radial velocity (Rv)–11.2[3] km/s
Proper motion (μ) RA: +15.14[1][2] mas/yr
Dec.: –53.43[1][2] mas/yr
Parallax (π)14.32 ± 0.29 mas[1][2]
Distance228 ± 5 ly
(70 ± 1 pc)
Absolute magnitude (MV)−2.17[6]
Details
Mass7.8±0.2[7] M☉
Radius4.5[8] R☉
Luminosity3,300[9] L☉
Temperature18,890[9] K
Rotational velocity (v sin i)165[10] km/s
Age31.4±0.4[7] Myr
Other designations
Nunki, Sadira[11][12], σ Sgr, Sigma Sgr, 34 Sagittarii, CPD−27  5241, FK5 706, GC 25941, HD 175191, HIP 92855, HR 7121, SAO 187448, PPM 269078, CCDM J18552-2618A, WDS J18553-2618Aa,Ab
Database references
SIMBADdata

Sigma Sagittarii, Latinized from σ Sagittarii; formally named Nunki /ˈnʌŋki/,[13][14] is the second-brightest star in the constellation of Sagittarius. It has an apparent magnitude of +2.05,[3] making it readily visible to the naked eye. The distance to this star, determined using parallax measurements from the Hipparcos astrometry satellite,[15] yields a value of approximately 228 light-years (70 parsecs) from the Sun.[1][2]

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  13. ^ Davis, George A. (1944). "The pronunciations, derivations, and meanings of a selected list of star names". Popular Astronomy. 52: 26. Bibcode:1944PA.....52....8D.
  14. ^ "Naming Stars". IAU.org. Retrieved 16 December 2017.
  15. ^ Cite error: The named reference GSM was invoked but never defined (see the help page).