Pi2 Gruis
Binary star system in the constellation Grus
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π2 Gruis, Latinised as Pi2 Gruis, is a binary star[3] system in the southern constellation of Grus. It is faintly visible to the naked eye as a yellow-white hued star with an apparent visual magnitude of 5.622.[2] Based upon an annual parallax shift of 25.1 mas as seen from the Earth,[1] the system is located 130 light years from the Sun.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Grus |
| Right ascension | 22h 23m 07.98704s[1] |
| Declination | −45° 55′ 42.5582″[1] |
| Apparent magnitude (V) | 5.622[2] (5.71 + 11.3)[3] |
| Characteristics | |
| Spectral type | F3 III-IV[4][3] or F0 V[5] |
| U−B color index | +0.016[2] |
| B−V color index | +0.365[2] |
| Astrometry | |
| Radial velocity (Rv) | 3.0[6] km/s |
| Proper motion (μ) | RA: +233.166[1] mas/yr Dec.: −58.205[1] mas/yr |
| Parallax (π) | 25.1061±0.1256 mas[1] |
| Distance | 129.9 ± 0.6 ly (39.8 ± 0.2 pc) |
| Absolute magnitude (MV) | 2.62[7] |
| Details | |
| π2 Gru A | |
| Mass | 1.37[8] M☉ |
| Radius | 1.93±0.07[1] R☉ |
| Luminosity | 7.15±0.04[1] L☉ |
| Surface gravity (log g) | 4.20[8] cgs |
| Temperature | 6788+138 −101[1] K |
| Metallicity [Fe/H] | −0.06[6] dex |
| Age | 758[8] Myr |
| Other designations | |
| π2 Gru, CD−46°14295, FK5 3786, HD 212132, HIP 110506, HR 8524, SAO 231111, WDS J22231-4556[9] | |
| Database references | |
| SIMBAD | data |
The primary, component A, is an F-type star of uncertain luminosity class. Malaroda (1975) gave it a stellar classification of F3 III-IV,[4] which would indicate an evolving subgiant/giant star hybrid spectrum, whereas Houk (1978) listed it as class F0 V,[5] suggesting that it is an F-type main sequence star. It has been considered to be a chemically peculiar star,[10] but this is now considered doubtful.[11] It is 758[8] million years old with 1.4[8] times the mass of the Sun. The star is 1.9[1] times the Sun's radius and is radiating 7[1] times the luminosity of the Sun from its photosphere at an effective temperature of 6,788 K.[1]
The companion is a magnitude 11.3 star at an angular separation of 4.6 arc seconds.[3] Gaia Data Release 2 has measured a separate annual parallax for it of 25.3266±0.0871 mas, almost identical to the primary star, and indicates that it is a red dwarf.[12]