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Zeta Sagittarii
Triple star system in the constellation Sagittarius / From Wikipedia, the free encyclopedia
Zeta Sagittarii (ζ Sagittarii, abbreviated Zeta Sgr, ζ Sgr) is a triple star system and the third-brightest star in the constellation of Sagittarius after Kaus Australis and Nunki. Based upon parallax measurements, it is about 88 light-years (27 parsecs) from the Sun.[1]
Quick Facts Constellation, Right ascension ...
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Sagittarius |
Right ascension | 19h 02m 36.73024s[1] |
Declination | –29° 52′ 48.2279″[1] |
Apparent magnitude (V) | +2.59[2] (3.27/3.48)[3] |
Characteristics | |
Spectral type | A2.5 Va[4] |
U−B color index | +0.05[2] |
B−V color index | +0.08[2] |
Astrometry | |
Radial velocity (Rv) | +22[5] km/s |
Proper motion (μ) | RA: +10.79[1] mas/yr Dec.: +21.11[1] mas/yr |
Parallax (π) | 36.98 ± 0.87 mas[1] |
Distance | 88 ± 2 ly (27.0 ± 0.6 pc) |
Absolute magnitude (MV) | 1.11/1.32[3] |
Orbit[3] | |
Period (P) | 21.00 ± 0.01 years |
Semi-major axis (a) | 0.489 ± 0.001″ |
Eccentricity (e) | 0.211 ± 0.001 |
Inclination (i) | 111.1 ± 0.1° |
Longitude of the node (Ω) | 74.0 ± 0.1° |
Periastron epoch (T) | 2005.99 ± 0.03 |
Argument of periastron (ω) (secondary) | 7.2 ± 0.6° |
Details | |
Mass | 5.26 ± 0.37[3] M☉ |
Surface gravity (log g) | 3.90[6] cgs |
Temperature | 8,799[6] K |
Rotational velocity (v sin i) | 77[7] km/s |
Age | 500–710[3] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Close
The three components are designated Zeta Sagittarii A (officially named Ascella /əˈsɛlə/, the traditional name for the entire system)[8][9] and B, themselves forming a binary pair, and a smaller companion star, C.