Astronomy:Pi Ceti

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Short description: Spectroscopic binary star system in the constellation Cetus
Pi Ceti
Location of Pi Ceti (circled)
Observation data
Equinox J2000.0]] (ICRS)
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[2] mas/yr
Dec.: −23.592[2] mas/yr
Parallax (π)8.4022 ± 0.1945[2] mas
Distance360+16
−13 ly
(109+5
−4 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
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[10] 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[11]
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 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] Spectroscopic measurements indicate a distance of approximately 360 light-years (109 parsecs).[9] The system is drifting further away from the Sun with a line of sight velocity component of +15 km/s.[7]

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 B-type star[13] that has been given stellar classifications of B7 V[5] and B7 IV.[6] The star shows no magnetic field but it does emit an infrared excess.[13]

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).[14] 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.[15]

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.[16]

References

  1. ↑ 1.0 1.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940.  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 Gutierrez-Moreno, Adelina et al. (1966), "A System of photometric standards", Publications of the Department of Astronomy University of Chile (Publicaciones Universidad de Chile, Department de Astronomy) 1: 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, doi:10.1051/0004-6361/201117691, Bibcode: 2012A&A...537A.120Z. 
  5. ↑ 5.0 5.1 Buscombe, W. (1962), "Spectral classification of Southern fundamental stars", Mount Stromlo Observatory Mimeogram 4: 1, Bibcode: 1962MtSOM...4....1B. 
  6. ↑ 6.0 6.1 Hohle, M. M. et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, doi:10.1002/asna.200911355, Bibcode: 2010AN....331..349H. 
  7. ↑ 7.0 7.1 Pourbaix, D. et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics 424 (2): 727–732. doi:10.1051/0004-6361:20041213. Bibcode: 2004A&A...424..727P. 
  8. ↑ 8.0 8.1 Lacy, C. H. S. et al. (March 1997), "The Spectroscopic Orbit of Pi Ceti", Astronomical Journal 113: 1088, doi:10.1086/118325, Bibcode: 1997AJ....113.1088L. 
  9. ↑ 9.0 9.1 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 .
  10. ↑ Prugniel, Ph. et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics 531: A165, doi:10.1051/0004-6361/201116769, Bibcode: 2011A&A...531A.165P. 
  11. ↑ "pi. Cet". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=pi.+Cet. 
  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, https://books.google.com/books?id=_QsVAQAAMAAJ&pg=RA1-PA8-IA1. 
  13. ↑ 13.0 13.1 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, doi:10.1111/j.1365-2966.2012.20718.x, Bibcode: 2012MNRAS.422.2072F. 
  14. ↑ Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc., 1963, p. 162, ISBN ((0-486-21079-0)), https://archive.org/details/starnamestheirlo00alle/page/162, retrieved 2010-12-12. 
  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, https://ntrs.nasa.gov/citations/19720005197, retrieved 2026-03-06. 
  16. ↑ Script error: The function "in_lang" does not exist. AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 12 日



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