Alpha Monocerotis

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Alpha Monocerotis
Diagram showing star positions and boundaries of the Monoceros constellation and its surroundings
Cercle rouge 100%.svg

Location of α Monocerotis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Monoceros
Right ascension 07h 41m 14.8324s
Declination –09° 33′ 04.071″
Apparent magnitude (V) 3.94[1]
Spectral type K0 III[1]
B−V color index 1.022[1]
Radial velocity (Rv) +10.50[1] km/s
Distance 144 ly
(44.2 pc)
Absolute magnitude (MV) 0.71 ± 0.08[2]
Mass 2.02 ± 0.29[2] M
Radius 10.1 ± 0.5[2] R
Surface gravity (log g) 2.71 ± 0.09[2] cgs
Temperature 4,879[2] K
Metallicity [Fe/H] −0.01[2] dex
Rotation 326 days[3]
Rotational velocity (v sin i) 1.9[3] km/s
Age 1.18 ± 0.42[2] Gyr
Other designations
26 Monocerotis, BD–09 2172, HD 61935, HIP 37447, HR 2970, IRAS 07388-0926, SAO 134986.

Alpha Monocerotis (α Mon, α Monocerotis) is the Bayer designation for a star in the equatorial constellation of Monoceros.

Alpha Monocerotis is the brightest star in the constellation Monoceros, It is nearing the end of its life. Internal changes have caused the star to puff up gas.

It is a giant star with a stellar classification of K0 III[1] and is of apparent magnitude 3.93. It is approximately 144 light years from Earth.


  1. ^ 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. 
  2. ^ a b c d e f g 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. 
  3. ^ a b 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. 

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