Gamma2 Sagittarii
3rd-magnitude K-type star in the constellation Sagittarius / From Wikipedia, the free encyclopedia
For other stars with this Bayer designation, see γ Sagittarii.
Gamma2 Sagittarii (γ2 Sagittarii, abbreviated Gamma2 Sgr, γ2 Sgr), formally named Alnasl /ælˈnæzəl/,[7] is a 3rd-magnitude star in the zodiac constellation of Sagittarius. The location of this star is in the handle of the Bow of Sagittarius the Centaur. It is approximately 32.6 parsecs (106 light-years) from the Sun and has an apparent visual magnitude of +2.96,[2] making it the seventh-brightest star in the constellation.
Quick Facts Constellation, Right ascension ...
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Sagittarius |
Right ascension | 18h 05m 48.484s[1] |
Declination | 30° 25′ 26.50″[1] |
Apparent magnitude (V) | +2.96[2] |
Characteristics | |
Evolutionary stage | K-type giant |
Spectral type | K0III[2] |
U−B color index | +0.77[3] |
B−V color index | +1.006[2] |
Astrometry | |
Radial velocity (Rv) | 22.0[4] km/s |
Proper motion (μ) | RA: −48.839 mas/yr[1] Dec.: −204.86 mas/yr[1] |
Parallax (π) | 30.6791 ± 0.4451 mas[2] |
Distance | 106.2+1.6 −1.5 ly (32.58+0.48 −0.47 pc)[2] |
Absolute magnitude (MV) | +0.395[2] |
Details[2] | |
Mass | 1.98±0.22 M☉ |
Radius | 12.07±0.27 R☉ |
Luminosity | 73.45±2.42 L☉ |
Surface gravity (log g) | 2.712±0.092 cgs |
Temperature | 4,864±36 K |
Metallicity [Fe/H] | −0.153±0.028 dex |
Other designations | |
Database references | |
SIMBAD | data |
Close
It forms part of a double star along with a fainter optical companion designated Gamma1 Sagittarii located about 50 arcminutes north of this star. The latter is a magnitude 4.7 Cepheid variable star that also has the variable star designation W Sagittarii.[8][9]