Pi Piscium

Pi Piscium (π Piscium) is a spectroscopic binary^[3] star in the zodiac constellation of Pisces. It is faintly visible to the naked eye, having an apparent visual magnitude of 5.60.^[2] Based upon an annual parallax shift of 28.50 mas as seen from Earth,^[1] it is 114 light years distant. It is a member of the thin disk population of the Milky Way.^[7]

Pi Piscium

Location of π Piscium (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Pisces
Right ascension	01h 37m 05.91523s[1]
Declination	+12° 08′ 29.5186″[1]
Apparent magnitude (V)	5.60[2] (5.56 + 9.56)[3]
Characteristics
Spectral type	F0 V[4] + KV[3]
Astrometry
Radial velocity (Rv)	−1.0[2] km/s
Proper motion (μ)	RA: −77.29[1] mas/yr Dec.: +9.13[1] mas/yr
Parallax (π)	28.50±0.97 mas[1]
Distance	114 ± 4 ly (35 ± 1 pc)
Absolute magnitude (MV)	+2.94[2]
Details[3]
A
Mass	1.42 M☉
Radius	1.68[a] R☉
Luminosity	5.45[b] L☉
Surface gravity (log g)	4.16 cgs
Temperature	6,810 K
Metallicity [Fe/H]	−0.10 dex
Rotational velocity (v sin i)	105.9[2] km/s
Age	2.0[5] Gyr
B
Mass	0.75 M☉
Radius	0.69[a] R☉
Luminosity	0.207[b] L☉
Temperature	4,700 K
Other designations
π Psc, 102 Piscium, BD+11°205, FK5 1046, GC 1954, HD 9919, HIP 7535, HR 463, SAO 92536, PPM 117498[6]
Database references
SIMBAD	data

The primary, of apparent magnitude 5.56,^[3] is an ordinary F-type main-sequence star with a stellar classification of F0 V.^[4] At the estimated age of two billion years,^[5] it is about 55% of the way through its main sequence lifetime^[8] and still has a relatively high rate of spin with a projected rotational velocity of 105.9 km/s.^[2] The star has 1.42 times the mass of the Sun and 1.68^[a] of the Sun's radius. It is radiating 5.5^[b] times the Sun's luminosity at an effective temperature of 6,810 K.^[3] At that temperature, Pi Piscium A has a yellow-white hue, as many F-type stars.^[9]

The secondary, of apparent magnitude 9.56, is a K-dwarf star. It is 0.75 times as massive than the Sun, 1.68^[a] times as large, and has 21%^[b] of the luminosity. Its effective temperature is 4,700 K,^[3] giving it an orange hue typical of K-type stars.^[9]

Analysis of its motion suggest Pi Piscium may be a member of the Ursa Major association, but higher-quality observations are needed to confirm this.^[3]

Naming

In Chinese, 右更 (Yòu Gèng), meaning Official in Charge of the Pasturing, refers to an asterism consisting of π Piscium, η Piscium, ρ Piscium, ο Piscium and 104 Piscium. Consequently, the Chinese name for π Piscium itself is 右更三 (Yòu Gèng sān, English: the Third Star of Official in Charge of the Pasturing.)^[10]

Notes

1. Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:$${\displaystyle {\sqrt {{\biggl (}{\frac {5,772}{6,810}}{\biggr )}^{4}\cdot 5.45}}=1.68\ R_{\odot }.}$$$${\displaystyle {\sqrt {{\biggl (}{\frac {5,772}{4,700}}{\biggr )}^{4}\cdot 0.207}}=0.69\ R_{\odot }.}$$
2. Calculated from the equation L = 10^{0.4 • (4.74 − M_bol}, where M_bol is the absolute bolometric magnitude. For component A, a value of 2.90 is used, while for B a value of 6.45 is used.