3 Piscis Austrini
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Microscopium |
| Right ascension | 21h 13m 17.32730s |
| Declination | −27° 37′ 09.7106″ |
| Apparent magnitude (V) | 5.39±0.01 |
| Characteristics | |
| Spectral type | K3 III |
| B−V color index | +1.42 |
| Astrometry | |
| Radial velocity (Rv) | −46.2±2.4 km/s |
| Proper motion (μ) | RA: +98.513 mas/yr Dec.: −110.906 mas/yr |
| Parallax (π) | 8.0734±0.1733 mas |
| Distance | 404 ± 9 ly (124 ± 3 pc) |
| Absolute magnitude (MV) | +0.19 |
| Details | |
| Mass | 1.58 M☉ |
| Radius | 31.3±1.6 R☉ |
| Luminosity | 184+9 −8 L☉ |
| Surface gravity (log g) | 1.86 cgs |
| Temperature | 4,225±123 K |
| Metallicity [Fe/H] | −0.17 dex |
| Rotational velocity (v sin i) | <1 km/s |
| Age | 2.59+0.83 −1.90 Gyr |
| Other designations | |
| 3 PsA, 58 G. Microscopii, CD−28°17178, CPD−28°7411, FK5 1556, GC 29652, HD 201901, HIP 104750, HR 8110, SAO 190129 | |
| Database references | |
| SIMBAD | data |
3 Piscis Austrini, also known as HD 201901 or simply 3 PsA, is an astrometric binary (100% chance) located in the southern constellation Microscopium. It was once part of Piscis Austrinus, the southern fish. The system has a combined apparent magnitude of 5.39, making it faintly visible to the naked eye under ideal conditions. Gaia DR3 parallax measurements imply a distance of 404 light years and it is currently approaching the Solar System with a heliocentric radial velocity of −46.2 km/s. At its current distance, 3 PsA's brightness is diminished by 0.12 magnitudes due to extinction from interstellar dust and it has an absolute magnitude of +0.19.
The visible component is an evolved red giant with a stellar classification of K3 III. The interferometry-measured angular diameter of the star, after correcting for limb darkening, is 2.03±0.04 mas, which, at its estimated distance, equates to a physical radius of about 20 times the radius of the Sun. However, its actual empirical radius is 31.3 R☉. It has 1.58 times the mass of the Sun and is radiating 184 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,225 K. 3 PsA is metal deficient with an iron abundance 68% that of the Sun ([Fe/H] = −0.17) and it spins too slowly for its projected rotational velocity to be measured accurately. It is estimated to be 2.59 billion years old based on Gaia DR3 models.