Pi Ceti

Pi Ceti
Location of Pi Ceti (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Cetus
Right ascension 02h 44m 07.348s
Declination −13° 51′ 31.28″
Apparent magnitude (V) 4.238
Characteristics
Evolutionary stage main sequence
Spectral type B7 V or B7 IV
U−B color index −0.396
B−V color index −0.130
Astrometry
Radial velocity (Rv)14.98±0.25 km/s
Proper motion (μ) RA: −8.394 mas/yr
Dec.: −23.592 mas/yr
Parallax (π)8.4022±0.1945 mas
Distance360+16
−13 ly
(109+5
−4 pc)
Absolute magnitude (MV)−1.16
Orbit
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
π Cet A
Mass4.0±0.1 M☉
Radius4.0±0.2 R☉
Luminosity398+28
−27 L☉
Surface gravity (log g)3.83±0.03 cgs
Temperature12,819±76 K
Metallicity [Fe/H]+0.28±0.16 dex
Rotational velocity (v sin i)19.9±0.1 km/s
Age155+36
−35 Myr
Other designations
π Cet, 89 Ceti, BD−14 519, FK5 97, HD 17081, HIP 12770, HR 811, SAO 148575
Database references
SIMBADdata

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 neighbouring constellation Eridanus, as on the diagram at right. It is visible to the naked eye as a point of light with an apparent visual magnitude of 4.238. Spectroscopic measurements indicate a distance of approximately 360 light-years (109 parsecs). The system is drifting further away from the Sun with a line of sight velocity component of +15 km/s.

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.

The primary, component A, is a B-type star that has been given stellar classifications of B7 V and B7 IV. The star shows no magnetic field but it does emit an infrared excess.

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). 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.

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.

References

  1. 1 2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023), "Gaia Data Release 3. Summary of the content and survey properties", Astronomy and Astrophysics, 674: A1, arXiv:2208.00211, Bibcode:2023A&A...674A...1G, doi:10.1051/0004-6361/202243940, S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 3 4 Gutierrez-Moreno, Adelina; et al. (1966), "A System of photometric standards", Publications of the Department of Astronomy University of Chile, 1, Publicaciones Universidad de Chile, Department de Astronomy: 1–17, Bibcode:1966PDAUC...1....1G.
  4. ↑ Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy and Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691.
  5. 1 2 Buscombe, W. (1962), "Spectral classification of Southern fundamental stars", Mount Stromlo Observatory Mimeogram, 4: 1, Bibcode:1962MtSOM...4....1B.
  6. 1 2 Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
  7. 1 2 Pourbaix, D.; et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088.
  8. 1 2 3 Aschenbrenner, P.; Przybilla, N. (2026-04-03), "Quantitative spectroscopy of single and multiple OB-type stars. Non-LTE spectrum analysis with machine learning", Astronomy and Astrophysics, arXiv:2604.03082.
  9. 1 2 Lacy, C. H. S.; et al. (March 1997), "The Spectroscopic Orbit of Pi Ceti", Astronomical Journal, 113: 1088, Bibcode:1997AJ....113.1088L, doi:10.1086/118325.
  10. ↑ Prugniel, Ph.; et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769, S2CID 54940439.
  11. ↑ "pi. Cet", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2026-03-06.
  12. ↑ Lovi, George (1957), Mayall, R. Newton (ed.), "Two misplaced stars", AAVSO Abstracts: papers presented at the 46th Spring meeting, May 31 – June 2, 1957, p. 4.
  13. 1 2 Folsom, C. P.; et al. (May 2012), "Chemical abundances of magnetic and non-magnetic Herbig Ae/Be stars", Monthly Notices of the Royal Astronomical Society, 422 (3): 2072–2101, arXiv:1202.1845, Bibcode:2012MNRAS.422.2072F, doi:10.1111/j.1365-2966.2012.20718.x, S2CID 119100447.
  14. ↑ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc., p. 162, ISBN 0-486-21079-0, retrieved 2010-12-12.{{citation}}: CS1 maint: ignored ISBN errors (link)
  15. ↑ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology, retrieved 2026-03-06.
  16. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 12 日 Archived 2011-05-22 at the Wayback Machine