Alpha Monocerotis
Alpha Monocerotis, Latinized 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]
  | |
| 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[1] mas |
| 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☉ |
| 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[5] |
| Rotational velocity (v sin i) | 1.9[5] km/s |
| Age | 1.18±0.42[4] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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.[7] 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.[5]
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.
- 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.
- 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.