Alpha Ceti

From Wikipedia the free encyclopedia

This article is about Menkar, one of the brightest stars in Cetus. For the Star Trek "Ceti Alpha" locations, see Star Trek II: The Wrath of Khan.
α Ceti
Location of α Ceti (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cetus
Right ascension 03h 02m 16.77307s[1]
Declination +04° 05′ 23.0596″[1]
Apparent magnitude (V) 2.53[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type M1.5 IIIa[4]
U−B color index +1.93[2]
B−V color index +1.64[2]
Astrometry
Radial velocity (Rv)−26.08±0.02[5] km/s
Proper motion (μ) RA: −10.41±0.51[1] mas/yr
Dec.: −76.85±0.36[1] mas/yr
Parallax (π)13.09 ± 0.44 mas[1]
Distance249 ± 8 ly
(76 ± 3 pc)
Absolute bolometric
magnitude (Mbol)		−3.2±0.3[4]
Details
Mass2.3±0.2;[6] 1.465–1.933[7] M☉
Radius100.2±3.4[7] R☉
Luminosity1,764±342[7] L☉
Surface gravity (log g)0.66±0.07[7] cgs
Temperature3,738±170[7] K
Metallicity [Fe/H]−0.24±0.09[7] dex
Rotational velocity (v sin i)6.9[8] km/s
Other designations
Menkar, 92 Ceti, HR 911, BD+03°419, HD 18884, SAO 110920, FK5 107, HIP 14135
Database references
SIMBADdata

Alpha Ceti (α Ceti, abbreviated Alpha Cet, α Cet), officially named Menkar /ˈmɛŋkɑːr/,[9][10] is the second-brightest star in the constellation of Cetus. It is a cool luminous red giant estimated to be about 250 light years away based on parallax.

Nomenclature

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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)[11] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[12] 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".[13]

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.)[14]

Characteristics

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A light curve for Alpha Ceti, plotted from Hipparcos data,[15] folded with the period derived by Koen and Eyer (2002)[16]

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.[4] It has more than twice the mass of the Sun[6] and, as a giant star, has expanded to about 100 times the Sun's radius.[7] 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).[7] The relatively low temperature gives Menkar the red hue of an M-type star.[17]

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,[3] 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.[18] It has been observed to periodically vary in brightness, but only with an amplitude of about one hundredth of a magnitude.[16]

Namesakes

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

References

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  1. ^ a b c d e 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. ^ a b c 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. ^ a b 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. ^ a b c 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. ^ a b 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. ^ a b c d e f g h Soubiran, C.; Creevey, O. L.; Lagarde, N.; Brouillet, N.; Jofré, P.; Casamiquela, L.; Heiter, U.; Aguilera-Gómez, C.; Vitali, S.; Worley, C.; de Brito Silva, D. (2024-02-01). "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. ^ 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.
  10. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  11. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  12. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  13. ^ Star Name - R.H. Allen p.160
  14. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日
  15. ^ "/ftp/cats/more/HIP/cdroms/cats". Centre de Données astronomiques de Strasbourg. Strasbourg astronomical Data Center. Retrieved 15 October 2022.
  16. ^ a b 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
  17. ^ "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
  18. ^ Kaler, James B., "MENKAR (Alpha Ceti)", Stars, University of Illinois, retrieved 2011-12-24
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