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Alpha Monocerotis

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α Monocerotis
Location of α Monocerotis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Monoceros
Right ascension 07h 41m 14.832s[1]
Declination −09° 33′ 04.078″[1]
Apparent magnitude (V) 3.94[2]
Characteristics
Spectral type G9.5 III-IIIb Fe-0.5[3]
B−V color index 1.022[2]
Astrometry
Radial velocity (Rv)+10.50[2] km/s
Proper motion (μ) RA: -74.989 mas/yr[1]
Dec.: -19.838 mas/yr[1]
Parallax (π)22.3839 ± 0.1348 mas[1]
Distance145.7 ± 0.9 ly
(44.7 ± 0.3 pc)[1]
Absolute magnitude (MV)0.71±0.08[4]
Details
Mass1.78±0.11[5] M☉
Radius10.05[5] – 10.42±0.12[6] R☉
Luminosity63.7±1.3[6] L☉
Surface gravity (log g)2.81±0.08[5] cgs
Temperature5049±32[6] K
Metallicity [Fe/H]−0.01±0.03[5] dex
Rotation326 days[7]
Rotational velocity (v sin i)1.9[7] km/s
Age1.824±0.283[5] Gyr
Other designations
α Mon, 26 Monocerotis, BD−09° 2172, HD 61935, HIP 37447, HR 2970, SAO 134986[8]
Database references
SIMBADdata

Alpha Monocerotis, Latinised from α Monocerotis, is the Bayer designation for the brightest star in the equatorial constellation of Monoceros. It can be viewed with the naked eye, having an apparent visual magnitude of 3.94.[2] Based upon an annual parallax shift of 22.4 mas as seen from Earth,[1] it is located 146 light-years away from the Sun. The star is moving away from the Sun with a radial velocity of +10.5 km/s.[2]

The stellar classification of G9.5 III-IIIb Fe-0.5[3] indicates this is an evolved giant star of type G, which means the hydrogen has been depleted at its core and the outer envelope has expanded and cooled. The 'Fe−0.5' notation indicates the spectrum displays a slight underabundance of iron relative to other stars of this temperature. It is a red clump giant, which means it is generating energy through helium fusion at its core.[9] At the age of 1.8 billion years, this yellow-hued star has an estimated two times the mass of the Sun and 10 times the Sun's radius.[5] It is spinning sedately with a rotation period of about 326 days.[7]

References

  1. ^ a b c d e f 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.
  2. ^ a b c d e Hekker, S.; et al. (August 2006), "Precise radial velocities of giant stars. I. Stable stars", Astronomy and Astrophysics, 454 (3): 943–949, arXiv:astro-ph/0604502, Bibcode:2006A&A...454..943H, doi:10.1051/0004-6361:20064946, S2CID 119529768.
  3. ^ a b Keenan, Philip C; McNeil, Raymond C (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  4. ^ da Silva, L.; et al. (November 2006), "Basic physical parameters of a selected sample of evolved stars", Astronomy and Astrophysics, 458 (2): 609–623, arXiv:astro-ph/0608160, Bibcode:2006A&A...458..609D, doi:10.1051/0004-6361:20065105, S2CID 9341088.
  5. ^ a b c d e f Gomes da Silva, J.; Santos, N. C.; Adibekyan, V.; Sousa, S. G.; Campante, T. L.; Figueira, P.; Bossini, D.; Delgado-Mena, E.; Monteiro, M. J. P. F. G.; de Laverny, P.; Recio-Blanco, A.; Lovis, C. (2021-02-01). "Stellar chromospheric activity of 1674 FGK stars from the AMBRE-HARPS sample. I. A catalogue of homogeneous chromospheric activity". Astronomy and Astrophysics. 646: A77. arXiv:2012.10199. Bibcode:2021A&A...646A..77G. doi:10.1051/0004-6361/202039765. ISSN 0004-6361. Alpha Monocerotis' database entry at VizieR.
  6. ^ a b c Baines, Ellyn K.; Armstrong, J. Thomas; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David; Nisley, Ishara; Sanborn, Jason; Schmitt, Henrique R.; Belle, Gerard T. van (October 2021). "Angular Diameters and Fundamental Parameters of Forty-four Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 162 (5): 198. arXiv:2211.09030. Bibcode:2021AJ....162..198B. doi:10.3847/1538-3881/ac2431. ISSN 1538-3881.
  7. ^ a b c Setiawan, J.; et al. (July 2004), "Precise radial velocity measurements of G and K giants. Multiple systems and variability trend along the Red Giant Branch", Astronomy and Astrophysics, 421: 241–254, Bibcode:2004A&A...421..241S, doi:10.1051/0004-6361:20041042-1.
  8. ^ "alf Mon". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-11-08.{{cite web}}: CS1 maint: postscript (link)
  9. ^ Laney, C. D.; Joner, M. D.; Pietrzyński, G. (2012), "A new Large Magellanic Cloud K-band distance from precision measurements of nearby red clump stars", Monthly Notices of the Royal Astronomical Society, 419 (2): 1637, arXiv:1109.4800, Bibcode:2012MNRAS.419.1637L, doi:10.1111/j.1365-2966.2011.19826.x, S2CID 117788450.{{citation}}: CS1 maint: unflagged free DOI (link)
  • Kaler, James B. (March 23, 2007), "Alpha Monocerotis", STARS, University of Illinois, retrieved 2017-11-08.
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