Alpha Ceti

α Ceti
Location of α Ceti (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Cetus
Right ascension 03h 02m 16.77307s
Declination +04° 05′ 23.0596″
Apparent magnitude (V) 2.53
Characteristics
Evolutionary stage AGB
Spectral type M1.5 IIIa
U−B color index +1.93
B−V color index +1.64
Astrometry
Radial velocity (Rv)−26.08±0.02 km/s
Proper motion (μ) RA: −10.41±0.51 mas/yr
Dec.: −76.85±0.36 mas/yr
Parallax (π)13.09±0.44 mas
Distance249 ± 8 ly
(76 ± 3 pc)
Absolute bolometric
magnitude (Mbol)		−3.2±0.3
Details
Mass2.3±0.2; 1.465–1.933 M☉
Radius100.2±3.4 R☉
Luminosity1,764±342 L☉
Surface gravity (log g)0.66±0.07 cgs
Temperature3,738±170 K
Metallicity [Fe/H]−0.24±0.09 dex
Rotational velocity (v sin i)6.9 km/s
Other designations
Menkar, α Cet, 92 Ceti, BD+03°419, FK5 107, HD 18884, HIP 14135, HR 911, SAO 110920
Database references
SIMBADdata

Alpha Ceti is the second-brightest star in the constellation of Cetus. Its official name is Menkar, pronounced /ˈmɛŋkɑːr/; Alpha Ceti is its Bayer designation, which is Latinized from α Ceti and abbreviated Alpha Cet or α Cet. This is a cool luminous red giant estimated to be about 250 light years away based on parallax.

Nomenclature

Alpha Ceti is the star's Bayer designation. It has the traditional name Menkar, deriving from the Arabic word منخر manħar "nostril" (of Cetus). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Menkar for this star.

This star, along with γ Cet (Kaffaljidhma), δ Cet, λ Cet (also Menkar), μ Cet, ξ1 Cet and ξ2 Cet were Al Kaff al Jidhmah, "the Part of a Hand".

In Chinese, 天囷 (Tiān Qūn), meaning Circular Celestial Granary, refers to an asterism consisting of α Ceti, κ1 Ceti, λ Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, γ Ceti, δ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for α Ceti itself is 天囷一 (Tiān Qūn yī, English: the First Star of Circular Celestial Granary.)

Characteristics

A light curve for Alpha Ceti, plotted from Hipparcos data, folded with the period derived by Koen and Eyer (2002)

Despite having the Bayer designation α Ceti, at visual magnitude 2.54 this star is actually not the brightest star in the constellation Cetus. That honor goes instead to Beta Ceti at magnitude 2.04. Menkar is a red giant with a stellar classification of M1.5 IIIa. It has more than twice the mass of the Sun and, as a giant star, has expanded to about 100 times the Sun's radius. The large area of the photosphere means that it is emitting about 1,765 times as much energy as the Sun, even though the effective temperature is only 3,738 K (compared to 5,778 K on the Sun). The relatively low temperature gives Menkar the red hue of an M-type star.

Menkar has evolved from the main sequence after exhausting the hydrogen at its core. It has also exhausted its core helium, becoming an asymptotic giant branch star, and will probably become a highly unstable star like Mira before finally shedding its outer layers and forming a planetary nebula, leaving a relatively large white dwarf remnant. It has been observed to periodically vary in brightness, but only with an amplitude of about one hundredth of a magnitude.

Namesakes

Menkar (AK-123) was a United States Navy Crater class cargo ship named after the star.

References

  1. 1 2 3 4 5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  2. 1 2 3 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  3. 1 2 Eggen, Olin J. (1992), "Asymptotic giant branch stars near the sun", The Astronomical Journal, 104: 275, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
  4. 1 2 3 Tsuji, T. (October 2008), "Cool luminous stars: the hybrid nature of their infrared spectra", Astronomy and Astrophysics, 489 (3): 1271–1289, arXiv:0807.4387, Bibcode:2008A&A...489.1271T, doi:10.1051/0004-6361:200809869, S2CID 19007399.
  5. ↑ Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
  6. 1 2 Wittkowski, M.; et al. (December 2006), "Tests of stellar model atmospheres by optical interferometry. IV. VINCI interferometry and UVES spectroscopy of Menkar", Astronomy and Astrophysics, 460 (3): 855–864, arXiv:astro-ph/0610150, Bibcode:2006A&A...460..855W, doi:10.1051/0004-6361:20066032, S2CID 16525827.
  7. 1 2 3 4 5 6 7 8 Soubiran, C.; et al. (February 2024), "Gaia FGK benchmark stars: Fundamental Teff and log g of the third version", Astronomy and Astrophysics, 682: A145, arXiv:2310.11302, Bibcode:2024A&A...682A.145S, doi:10.1051/0004-6361/202347136, ISSN 0004-6361. Menkar's database entry at VizieR.
  8. ↑ Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209, S2CID 121883397.
  9. ↑ "alf Cet", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2026-02-10.
  10. ↑ Kunitzsch, Paul; Smart, Tim (2006), A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.), Cambridge, Massachusetts: Sky Pub, ISBN 978-1-931559-44-7.
  11. ↑ IAU Catalog of Star Names, retrieved 28 July 2016.
  12. ↑ IAU Working Group on Star Names (WGSN), archived from the original on 10 June 2016, retrieved 22 May 2016.
  13. ↑ Bulletin of the IAU Working Group on Star Names, No. 1 (PDF), retrieved 28 July 2016.
  14. ↑ Allen, R. H., Star Name, p. 160.
  15. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日 Archived 2012-02-04 at the Wayback Machine
  16. ↑ "/ftp/cats/more/HIP/cdroms/cats", Centre de Données astronomiques de Strasbourg, Strasbourg astronomical Data Center, retrieved 15 October 2022.
  17. 1 2 Koen, Chris; Eyer, Laurent (2002), "New periodic variables from the Hipparcos epoch photometry", Monthly Notices of the Royal Astronomical Society, 331 (1): 45, arXiv:astro-ph/0112194, Bibcode:2002MNRAS.331...45K, doi:10.1046/j.1365-8711.2002.05150.x.
  18. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16.
  19. ↑ Kaler, James B., "MENKAR (Alpha Ceti)", Stars, University of Illinois, retrieved 2011-12-24.