Pi Ceti
Spectroscopic binary star system in the constellation Cetus
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Pi Ceti a binary star system in the equatorial constellation of Cetus. Its name is a Bayer designation that is Latinized from π Ceti, and abbreviated Pi Cet or π Cet. The system is located near the eastern boundary of the constellation and is sometimes portrayed as forming part of the Eridanus constellation's asterism.[12] It is visible to the naked eye as a point of light with an apparent visual magnitude of 4.238.[3] Observed to have a half yearly parallax shift of 8.30 mas as seen from Earth,[2] it is located at a distance of approximately 393 light years from the Sun. The system is drifting further away from the Sun with a line of sight velocity component of +15 km/s.[7]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cetus[1] |
| Right ascension | 02h 44m 07.348s[2] |
| Declination | −13° 51′ 31.28″[2] |
| Apparent magnitude (V) | 4.238[3] |
| Characteristics | |
| Evolutionary stage | main sequence[4] |
| Spectral type | B7 V[5] or B7 IV[6] |
| U−B color index | −0.396[3] |
| B−V color index | −0.130[3] |
| Astrometry | |
| Radial velocity (Rv) | 14.98±0.25[7] km/s |
| Proper motion (μ) | RA: −8.394 mas/yr[2] Dec.: −23.592 mas/yr[2] |
| Parallax (π) | 8.4022±0.1945 mas[2] |
| Distance | 388 ± 9 ly (119 ± 3 pc) |
| Absolute magnitude (MV) | −1.16[1] |
| Orbit[8] | |
| Period (P) | 2,722±14 d |
| Eccentricity (e) | 0.00±0.07 |
| Periastron epoch (T) | 2444852±29 JD |
| Argument of periastron (ω) (secondary) | 0.0° |
| Semi-amplitude (K1) (primary) | 4.33±0.25 km/s |
| Details[9] | |
| 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[10] 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[11] | |
| 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.[8]
The primary, component A, is a normal B-type star[9] that has been given stellar classifications of B7 V[5] and B7 IV.[6] 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.[9]
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).[13] 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.[14]
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.[15]