Gamma Piscis Austrini
Triple star system in the constellation Piscis Austrinus
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Gamma Piscis Austrini, Latinized from γ Piscis Austrini, is three-star system[7] in the southern constellation of Piscis Austrinus. It is visible to the naked eye with a combined apparent visual magnitude of +4.448.[2] Based upon an annual parallax shift of 15.1 mas as seen from the Earth,[1] the system is located about 216 light years from the Sun.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Piscis Austrinus |
| Right ascension | 22h 52m 31.5351s[1] |
| Declination | −32° 52′ 31.806″[1] |
| Apparent magnitude (V) | +4.448[2] (4.59 + 8.20)[3] |
| Characteristics | |
| γ PsA A | |
| Spectral type | A0 Vp(SrCrEu)[4] |
| U−B color index | −0.038[2] |
| B−V color index | −0.046[2] |
| γ PsA B | |
| Spectral type | F5 V[5] |
| U−B color index | −0.08[5] |
| B−V color index | +0.44[5] |
| Astrometry | |
| Radial velocity (Rv) | 16.5±2.7[6] km/s |
| Proper motion (μ) | RA: −32.73 mas/yr[1] Dec.: −21.21 mas/yr[1] |
| Parallax (π) | 15.14±0.57 mas[1] |
| Distance | 215 ± 8 ly (66 ± 2 pc) |
| Absolute magnitude (MV) | −0.20/3.50[5] |
| Details[7] | |
| Aa | |
| Mass | 2.65 M☉ |
| Radius | 2.9 R☉ |
| Surface gravity (log g) | 3.92[8] cgs |
| Temperature | 9,950 K |
| Rotation | 2.542±0.001 d |
| Rotational velocity (v sin i) | 47[8] km/s |
| Age | 350 Myr |
| Ab | |
| Mass | 0.94 M☉ |
| Radius | 0.84 R☉ |
| Temperature | 5,500 K |
| B | |
| Mass | 1.20 M☉ |
| Radius | 1.15 R☉ |
| Temperature | 6,400 K |
| Other designations | |
| γ PsA, 22 Piscis Austrini, CD−33°16270, HD 216336, HIP 112948, HR 8695, SAO 214153, WDS J22525-3253AB[9] | |
| Database references | |
| SIMBAD | γ PsA |
| γ PsA A | |
| γ PsA B | |
The A and B components, as of 2010, are separated by 4 arc seconds in the sky along a position angle of 255°.[10] The "A" component is itself a binary, made up of two stars orbiting each other with an estimated orbital period of 15 years and a separation of nine astronomical units,[7] with a combined apparent magnitude of 4.59.[3] The component Aa has 2.65 times more mass than the Sun and 2.9 times its radius, being a chemically peculiar star[7] with a spectral type A0 Vp(SrCrEu).[4] The Ab component is smaller, at 0.94 times the Sun's mass and 0.84 times its radius.[7] The fainter magnitude 8.20[3] companion, component B, is an F-type main sequence star with a class of F5 V.[5] It has 20% more mass than the Sun and a radius 15% larger.[7]
Gamma Piscis Austrini is moving through the Galaxy at a speed of 24.1 km/s relative to the Sun. Its projected Galactic orbit carries it between 21,605 and 30,903 light-years from the center of the Galaxy. It came closest to the Sun 1.8 million years ago at a distance of 157 light-years.[11]
The current age of the system is 350 million years. It will become a triple white dwarf system within 14 billion years.[7]
Naming
In Chinese, 敗臼 (Bài Jiù), meaning Decayed Mortar, refers to an asterism consisting of refers to an asterism consisting of γ Piscis Austrini, γ Gruis, λ Gruis and 19 Piscis Austrini. Consequently, the Chinese name for γ Piscis Austrini itself is 敗臼三 (Bài Jiù sān, English: the Third Star of Decayed Mortar.)[12]