Alpha Monocerotis
Star in the constellation Monoceros
From Wikipedia, the free encyclopedia
Alpha Monocerotis, Latinised from α Monocerotis, is the Bayer designation for a star in the equatorial constellation of Monoceros. It can be viewed with the naked eye, having an apparent visual magnitude of 3.94.[2] Despite being labeled "alpha", it is not the brightest star in the constellation; Beta Monocerotis is, though the individual stars of the latter are fainter.[10] 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 +11.7 km/s.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Monoceros |
| Right ascension | 07h 41m 14.832s[1] |
| Declination | −09° 33′ 04.08″[1] |
| Apparent magnitude (V) | 3.94[2] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | G9.5 III-IIIb Fe-0.5[4] |
| B−V color index | 1.022[2] |
| Astrometry | |
| Radial velocity (Rv) | 11.66±0.06[5] 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] |
| Distance | 145.7 ± 0.9 ly (44.7 ± 0.3 pc)[1] |
| Absolute magnitude (MV) | 0.71±0.08[6] |
| Details | |
| Mass | 2.25±0.13[5] M☉ |
| Radius | 10.42±0.12[7] R☉ |
| Luminosity | 63.7±1.3[7] L☉ |
| Surface gravity (log g) | 2.79±0.04[5] cgs |
| Temperature | 5049±32[7] K |
| Metallicity [Fe/H] | −0.04±0.03[5] dex |
| Rotation | 326 days[8] |
| Rotational velocity (v sin i) | 0.92±0.45[5] km/s |
| Age | 890±180[5] Myr |
| Other designations | |
| α Mon, 26 Monocerotis, BD−09°2172, HD 61935, HIP 37447, HR 2970, SAO 134986[9] | |
| Database references | |
| SIMBAD | data |
The stellar classification of G9.5 III-IIIb Fe-0.5[4] 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.[3] At the age of 890 million years, this yellow-hued star has an estimated 2.2 times the mass of the Sun[5] and 10 times the Sun's radius.[7] It is spinning sedately with a rotation period of about 326 days.[8]