Alpha Monocerotis

α Monocerotis
	Location of α Monocerotis (circled)
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Monoceros
Right ascension	07h 41m 14.833s[1]
Declination	−09° 33′ 04.07″[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: −74.61±0.14[1] mas/yr ; Dec.: −19.59±0.10[1] mas/yr
Parallax (π)	22.07 ± 0.18 mas[1]
Distance	148 ± 1 ly ; (45.3 ± 0.4 pc)
Absolute magnitude (MV)	0.71±0.08[4]
Details
Mass	2.02±0.29[4] M☉
Radius	10.1±0.5[4] R☉
Luminosity	63.7±1.3[5] L☉
Surface gravity (log g)	2.71±0.09[4] cgs
Temperature	4,879[4] K
Metallicity [Fe/H]	−0.01[4] dex
Rotation	326 days[6]
Rotational velocity (v sin i)	1.9[6] km/s
Age	1.18±0.42[4] Gyr
Other designations
	α Mon, 26 Monocerotis, BD−09° 2172, HD 61935, HIP 37447, HR 2970, SAO 134986[7]
Database references
SIMBAD	data

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 22.07 mas as seen from Earth,[1] it is located 148 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.[8] At the age of 1.18 billion years, this yellow-hued star has an estimated two times the mass of the Sun and 10 times the Sun's radius.[4] It is spinning sedately with a rotation period of about 326 days.[6]

References

van Leeuwen, F. (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. Vizier catalog entry
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.
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.
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.
Baines, Ellyn K.; Thomas Armstrong, J.; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David; Nisley, Ishara; Sanborn, Jason; Schmitt, Henrique R.; Van Belle, Gerard T. (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. S2CID 238998021.
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.
"alf Mon". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-11-08.{{cite web}}: CS1 maint: postscript (link)
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.

External links

Kaler, James B. (March 23, 2007), "Alpha Monocerotis", STARS, University of Illinois, retrieved 2017-11-08.

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[van_Leeuwen2007-1] van Leeuwen, F. (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. Vizier catalog entry

[aaa454_3_943-2] 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.

[perkins1989-3] 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.

[aaa458_2_609-4] 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.

[Baines-5] Baines, Ellyn K.; Thomas Armstrong, J.; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David; Nisley, Ishara; Sanborn, Jason; Schmitt, Henrique R.; Van Belle, Gerard T. (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. S2CID 238998021.

[aaa421_241-6] 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.

[SIMBAD-7] "alf Mon". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-11-08.{{cite web}}: CS1 maint: postscript (link)

[laney2012-8] 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.