Pi Ceti

Pi Ceti, Latinized from π Ceti, is the Bayer designation for a star system in the equatorial constellation of Cetus. It is visible to the naked eye with an apparent visual magnitude of 4.238.^[2] Observed to have an Earth half yearly parallax shift of 8.30 mas,^[1] it is around 393 light years from the Sun.

Pi Ceti

Location of Pi Ceti (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Cetus
Right ascension	02h 44m 07.34928s[1]
Declination	−13° 51′ 31.3130″[1]
Apparent magnitude (V)	4.238[2]
Characteristics
Spectral type	B7 V[3] or B7 IV[4]
U−B color index	−0.396[2]
B−V color index	−0.130[2]
Astrometry
Proper motion (μ)	RA: −8.62[1] mas/yr Dec.: −9.07[1] mas/yr
Parallax (π)	8.30±0.21 mas[1]
Distance	393 ± 10 ly (120 ± 3 pc)
Absolute magnitude (MV)	−1.16[5]
Orbit[6]
Period (P)	2,722±14 d
Eccentricity (e)	0.0±0.7
Periastron epoch (T)	2444852 ± 29 JD
Argument of periastron (ω) (secondary)	0.0°
Semi-amplitude (K1) (primary)	4.33±0.25 km/s
Details[7]
π Cet A
Mass	4.4±0.2 M☉
Radius	4.3±0.3 R☉
Luminosity	468 L☉
Surface gravity (log g)	3.8±0.2 cgs
Temperature	12,900±400 K
Metallicity [Fe/H]	0.28±0.16[8] dex
Rotational velocity (v sin i)	20.9±1.2 km/s
Age	0.3+0.1 −0.1 Myr
Other designations
π Cet, 89 Ceti, BD−14 519, FK5 97, HD 17081, HIP 12770, HR 811, SAO 148575.[9]
Database references
SIMBAD	data

This is a single-lined spectroscopic binary system with a nearly circular orbit and a period of 7.45 years. The fact that the system has a negligible eccentricity is surprising for such a long period, and may suggest that the secondary is a white dwarf that had its orbit circularized during a mass-transfer event.^[6]

The primary, component A, is a normal B-type star^[7] that has been given stellar classifications of B7 V^[3] and B7 IV.^[4] It appears very young – less than half a million years in age – and may still be on a pre-main sequence track. The star shows no magnetic field but it does emit an infrared excess.^[7]

Name

This star, along with ε Cet, ρ Cet and σ Cet, was Al Sufi's Al Sadr al Ḳaiṭos, the Whale's breast/chest (upper torso).^[10] Per Jack Rhoads's Reduced Star Catalog Containing 537 Named Stars, Al Sufi's numerically ordered stars (1 to 4), were ρ (rho), σ (sigma), ε (epsilon) and this star.^[11]

In Chinese, 天苑 (Tiān Yuàn), meaning Celestial Meadows, refers to an asterism consisting of π Ceti, and 15 stars in Eridanus: γ, π, δ, ε, ζ, η, and the string of τ (Tau)¹, ², ³, ⁴, ⁵, ⁶, ⁷, ⁸ and ⁹. Consequently, the Chinese name for the star is 天苑七 (Tiān Yuàn qī) meaning Celestial Meadows: seven.^[12]