Nu2 Sagittarii
Star in the constellation Sagittarius
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Nu2 Sagittarii (ν2 Sagittarii) is a binary star[8] system in the zodiac constellation of Sagittarius. It is faintly visible to the naked eye, having an apparent visual magnitude of +4.98;[2] it is 0.16 degree north of the ecliptic. The annual parallax shift of 11.91 mas as seen from Earth,[1] indicates this system is roughly 270 light years from the Sun. Nu2 Sagittarii has a high peculiar velocity of 86.0+11.6
−14.4 km/s and is most likely a runaway star system.[3]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 55m 07.14098s[1] |
| Declination | −22° 40′ 16.8185″[1] |
| Apparent magnitude (V) | +4.98[2] |
| Characteristics | |
| Spectral type | K1 Ib–II[3] |
| B−V color index | +1.32[2] |
| Astrometry | |
| Radial velocity (Rv) | −109.6[2] km/s |
| Proper motion (μ) | RA: −109.04[1] mas/yr Dec.: −35.25[1] mas/yr |
| Parallax (π) | 11.91±0.52 mas[1] |
| Distance | 270 ± 10 ly (84 ± 4 pc) |
| Absolute magnitude (MV) | +0.38[4] |
| Details | |
| ν2 Sgr A | |
| Mass | 1.44[2] M☉ |
| Radius | 85[5] R☉ |
| Luminosity | 120[2] L☉ |
| Surface gravity (log g) | 1.03[6] cgs |
| Temperature | 4,244±57[2] K |
| Metallicity [Fe/H] | −0.13[6] dex |
| Age | 4.52[2] Gyr |
| Other designations | |
| ν2 Sgr, 35 Sgr, BD−22°4915, HD 175190, HIP 92845, HR 7120, SAO 187445[7] | |
| Database references | |
| SIMBAD | data |
The spectrum of the primary component displays a stellar classification of K1 Ib–II,[3] indicating this is a K-type star with a mixed luminosity class of an evolved bright giant/supergiant star. It is a mild barium star, showing an enhanced abundance of s-process elements in its outer atmosphere. This material was most likely acquired during a previous mass transfer from its now white dwarf companion.[9] The primary has an estimated 1.4[2] times the mass of the Sun and has expanded to 85[5] times the Sun's radius.