Eta Piscis Austrini
Star in the constellation Piscis Austrinus
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Eta Piscis Austrini (η Piscis Austrini) is a binary star[2] system in the southern constellation of Piscis Austrinus. As of 2000, the two components had an angular separation of 1.818 arc seconds along a position angle of 113.4°. The pair have a combined apparent visual magnitude of +5.43,[5] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 3.99 mas as seen from the Earth,[13] the system is located roughly 820 light years from the Sun.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Piscis Austrinus |
| A | |
| Right ascension | 22h 00m 50.22454s[1] |
| Declination | â28° 27â² 13.4587â³[1] |
| Apparent magnitude (V) | 5.78[2] |
| B | |
| Right ascension | 22h 00m 50.34936s[3] |
| Declination | â28° 27â² 14.1460â³[3] |
| Apparent magnitude (V) | 6.80[2] |
| Characteristics | |
| Spectral type | B6 III shell + B8.5 V[4] |
| UâB color index | â0.30[5] |
| BâV color index | â0.10[5] |
| Variable type | suspected[6] |
| Astrometry | |
| Absolute magnitude (MV) | â1.53[7] |
| A | |
| Proper motion (μ) | RA: +15.289[1] mas/yr Dec.: â0.096[1] mas/yr |
| Parallax (Ï) | 3.8087±0.0932 mas[1] |
| Distance | 860 ± 20 ly (263 ± 6 pc) |
| B | |
| Proper motion (μ) | RA: +17.554[3] mas/yr Dec.: â1.229[3] mas/yr |
| Parallax (Ï) | 4.5342±0.3306 mas[3] |
| Distance | 720 ± 50 ly (220 ± 20 pc) |
| Details | |
| η PsA A | |
| Mass | 4.01±0.18[8] Mâ |
| Luminosity | 881[9] Lâ |
| Surface gravity (log g) | 3.48[9] cgs |
| Temperature | 12,310[9] K |
| Rotational velocity (v sin i) | 320[9] km/s |
| Age | 115[10] Myr |
| η PsA B | |
| Mass | 3.6[11] Mâ |
| Surface gravity (log g) | 4.17[11] cgs |
| Temperature | 14,144[11] K |
| Metallicity [Fe/H] | â0.21[11] dex |
| Other designations | |
| η PsA, 12 Piscis Austrini, CPDâ29°6659, HD 209014, HIP 108661, HR 8386, SAO 190822, WDS J22008-2827AB[12] | |
| Database references | |
| SIMBAD | data |
Although not catalogued formally as a variable star, brightness changes between magnitude 5,33 and 5.44 have been widely reported.[6][14] The type of variability is thought to be related to its rapid rotation and a surrounding shell, and is tentatively given as a combination of a Be star and Maia variable.[15]
The magnitude 5.8 primary, component A,[2] is a blue-white hued Be star[10] with a stellar classification B6 III.[4] At 115 million years old,[10] the star is spinning rapidly with a projected rotational velocity of 265.[8] It has an estimated four times the mass of the Sun and is radiating 604 times the solar luminosity at an effective temperature of 11,272 K.[8] The secondary, component B, has a visual magnitude of 6.8[2] and a spectral class of B8.5 V.[4]