Theta Piscium
Star in the constellation Pisces
From Wikipedia, the free encyclopedia
Theta Piscium, Latinized from θ Piscium, is a single,[7] 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,[1] 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.[2] The star is moving away from the Sun with a radial velocity of +6 km/s.[2]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Pisces |
| Right ascension | 23h 27m 58.09529s[1] |
| Declination | +06° 22â² 44.3720â³[1] |
| Apparent magnitude (V) | 4.27[2] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | K1 III[2] |
| UâB color index | +1.00 |
| BâV color index | +1.062[2] |
| Astrometry | |
| Radial velocity (Rv) | +6.05±0.19[2] km/s |
| Proper motion (μ) | RA: â123.83[1] mas/yr Dec.: â43.26[1] mas/yr |
| Parallax (Ï) | 21.96±0.25 mas[1] |
| Distance | 149 ± 2 ly (45.5 ± 0.5 pc) |
| Absolute magnitude (MV) | +0.83[2] |
| Details | |
| Mass | 1.58[4] Mâ |
| Radius | 11[5] Râ |
| Luminosity | 51.3[5] Lâ |
| Surface gravity (log g) | 2.70[3] cgs |
| Temperature | 4,684±23[4] K |
| Metallicity [Fe/H] | 0.06[3] dex |
| Rotational velocity (v sin i) | 3.1[5] km/s |
| Age | 2.45[4] Myr |
| Other designations | |
| θ Psc, 10 Piscium, BD+05°5173, FK5 1614, GC 32647, HD 220954, HIP 115830, HR 8916, SAO 128196, PPM 174110[6] | |
| Database references | |
| SIMBAD | data |
At the estimated age of 2.5 billion years,[4] this is an aging giant star with a stellar classification of K1 III,[2] 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.[3] Theta Piscium has 158%[4] of the Sun's mass and its outer atmosphere has swollen to about 11[5] times the girth of the Sun. It is brighter yet cooler than the Sun, radiating 51.3[5] times the Sun's luminosity from its enlarged photosphere at an effective temperature of about 4,684 K.[4]
Naming
In Chinese, é¹é (PÄ« Lì), meaning Thunderbolt, refers to an asterism consisting of refers to an asterism consisting of θ Piscium, β Piscium, γ Piscium, ι Piscium and Ï Piscium. Consequently, the Chinese name for θ Piscium itself is é¹éä¸ (PÄ« Lì sÄn, English: the Third Star of Thunderbolt.)[8]