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] |
Distance | 228 ± 5 ly (70 ± 1 pc) |
Absolute magnitude (MV) | −2.17[6] |
Details | |
Mass | 7.8±0.2[7] M☉ |
Radius | 4.5[8] R☉ |
Luminosity | 3,300[9] L☉ |
Temperature | 18,890[9] K |
Rotational velocity (v sin i) | 165[10] km/s |
Age | 31.4±0.4[7] Myr |
Other designations | |
Database references | |
SIMBAD | data |
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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