Astronomy:Alpha Ceti

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Short description: Red giant star in the constellation Cetus
α Ceti
Cetus constellation map.svg
Red circle.svg
Location of α Ceti (circled)
Observation data
Equinox J2000.0]] (ICRS)
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[1] mas
Distance249 ± 8 ly
(76 ± 3 pc)
Absolute magnitude (MV)−3.2±0.3[4]
Details
Mass2.3±0.2[6] M☉
Radius89±5[6] R☉
Luminosity1,455±328[6] L☉
Surface gravity (log g)0.9±0.1[6] cgs
Temperature3,795±70[6] K
Metallicity [Fe/H]0.00±0.30[6] dex
Rotational velocity (v sin i)6.9[7] 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/,[8][9] 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

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

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.)[13]

Structure

A light curve for Alpha Ceti, plotted from Hipparcos data,[14] folded with the period derived by Koen and Eyer (2002)[15]

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 89 times the Sun's radius. The large area of the photosphere means that it is emitting about 1,455 times as much energy as the Sun, even though the effective temperature is only 3,795 K (compared to 5,778 K on the Sun). The relatively low temperature gives Menkar the red hue of an M-type star.[16]

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.[17] It has been observed to periodically vary in brightness, but only with an amplitude of about one hundredth of a magnitude.[15]

Namesakes

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

See also

  • Alpha Ceti in fiction

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V 
  2. ↑ 2.0 2.1 2.2 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. ↑ 3.0 3.1 Eggen, Olin J. (1992), "Asymptotic giant branch stars near the sun", The Astronomical Journal 104: 275, doi:10.1086/116239, Bibcode: 1992AJ....104..275E 
  4. ↑ 4.0 4.1 Tsuji, T. (October 2008), "Cool luminous stars: the hybrid nature of their infrared spectra", Astronomy and Astrophysics 489 (3): 1271–1289, doi:10.1051/0004-6361:200809869, Bibcode: 2008A&A...489.1271T 
  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, doi:10.1051/0004-6361:20041272, Bibcode: 2005A&A...430..165F 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 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, doi:10.1051/0004-6361:20066032, Bibcode: 2006A&A...460..855W 
  7. ↑ 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, doi:10.1088/0004-6256/135/1/209, Bibcode: 2008AJ....135..209M 
  8. ↑ 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. 
  9. ↑ "IAU Catalog of Star Names". http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt. 
  10. ↑ "IAU Working Group on Star Names (WGSN)". https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  11. ↑ "Bulletin of the IAU Working Group on Star Names, No. 1". http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf. 
  12. ↑ Star Name - R.H. Allen p.160
  13. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日
  14. ↑ "/ftp/cats/more/HIP/cdroms/cats". Strasbourg astronomical Data Center. https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats. 
  15. ↑ 15.0 15.1 Koen, Chris; Eyer, Laurent (2002), "New periodic variables from the Hipparcos epoch photometry", Monthly Notices of the Royal Astronomical Society 331 (1): 45, doi:10.1046/j.1365-8711.2002.05150.x, Bibcode: 2002MNRAS.331...45K 
  16. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16 
  17. ↑ Kaler, James B., "MENKAR (Alpha Ceti)", Stars (University of Illinois), http://stars.astro.illinois.edu/sow/menkar.html, retrieved 2011-12-24 

External links

Coordinates: Sky map 03h 02m 16.77307s, +04° 05′ 23.0596″



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