Theta Piscium
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Pisces |
| Right ascension | 23h 27m 58.09529s |
| Declination | +06° 22′ 44.3720″ |
| Apparent magnitude (V) | 4.27 |
| Characteristics | |
| Evolutionary stage | red clump |
| Spectral type | K1 III |
| U−B color index | +1.00 |
| B−V color index | +1.062 |
| Astrometry | |
| Radial velocity (Rv) | +6.05±0.19 km/s |
| Proper motion (μ) | RA: −123.83 mas/yr Dec.: −43.26 mas/yr |
| Parallax (π) | 21.96±0.25 mas |
| Distance | 149 ± 2 ly (45.5 ± 0.5 pc) |
| Absolute magnitude (MV) | +0.83 |
| Details | |
| Mass | 1.58 M☉ |
| Radius | 11 R☉ |
| Luminosity | 51.3 L☉ |
| Surface gravity (log g) | 2.70 cgs |
| Temperature | 4,684±23 K |
| Metallicity [Fe/H] | 0.06 dex |
| Rotational velocity (v sin i) | 3.1 km/s |
| Age | 2.45 Myr |
| Other designations | |
| θ Psc, 10 Piscium, BD+05°5173, FK5 1614, GC 32647, HD 220954, HIP 115830, HR 8916, SAO 128196, PPM 174110 | |
| Database references | |
| SIMBAD | data |
Theta Piscium, Latinized from θ Piscium, is a single, orange-hued star in the zodiac constellation of Pisces, the fish. The annual parallax shift of this star was measured during the Hipparcos mission as 21.96 mas, which yields a distance estimate of about 149 light years. It is a faint star but visible to the naked eye with an apparent visual magnitude of 4.27. The star is moving away from the Sun with a radial velocity of +6 km/s.
At the estimated age of 2.5 billion years, this is an aging giant star with a stellar classification of K1 III, which means it has exhausted the supply of hydrogen at its core. It is a red clump star, indicating it is on the horizontal branch of its evolution and is generating energy through helium fusion at its core. Theta Piscium has 158% of the Sun's mass and its outer atmosphere has swollen to about 11 times the girth of the Sun. It is brighter yet cooler than the Sun, radiating 51.3 times the Sun's luminosity from its enlarged photosphere at an effective temperature of about 4,684 K.