Alpha Microscopii

Alpha Microscopii (α Microscopii) is a star in the southern constellation of Microscopium.[1] It is visible to the naked eye with an apparent visual magnitude that varies between 4.88 and 4.94.[2] Based upon an annual parallax shift of 8.2214 mas as seen from the Earth, it is located 400 ± 30 light years from the Sun. The star is moving nearer to the Sun with a radial velocity of −15 km/s.[1]

α Microscopii
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Microscopium
Right ascension  20h 49m 58.0821s[1]
Declination −33° 46′ 47.000″[1]
Apparent magnitude (V) 4.88 to 4.94[2]
Characteristics
Spectral type G7III[1]
U−B color index +0.73[3]
B−V color index +1.00[3]
Astrometry
Radial velocity (Rv)−14.5 ± 0.9[1] km/s
Proper motion (μ) RA: 3.71[1] mas/yr
Dec.: −20.19[1] mas/yr
Parallax (π)8.2214 ± 0.6173[4] mas
Distance400 ± 30 ly
(122 ± 9 pc)
Absolute magnitude (MV)−0.45 ± 0.20[5]
Details
Mass3.13 ± 0.18[5] M☉
Radius16.4 ± 1.6[5] R☉
Luminosity160[6] L☉
Surface gravity (log g)2.47 ± 0.07[5] cgs
Temperature4,923[5] K
Metallicity [Fe/H]+0.03[5] dex
Age0.36 ± 0.07[5] Gyr
Other designations
α Mic, Alpha Mic, HJ 5224A, CCDM J20500-3347A, CD−34 14660, CPD−34 8799, GC 29026, HD 198232, HIP 102831, HR 7965, IDS 20437-3409 A, PPM 300665, SAO 212472, WDS 20500-3347A.[1][7]
Database references
SIMBADdata

This is an evolved giant star of type G with a stellar classification of G7 III.[1] At the age of 360 million years, it has an estimated 3.1 times the mass of the Sun and has expanded to around 16 times the Sun's radius.[5] The star is radiating 160[6] times the Sun's luminosity from its expanded photosphere at an effective temperature of 4,923 K.[5]

This star has an optical visual companion, CCDM J20500-3347B, of apparent visual magnitude 10.0 approximately 20.4 arcseconds away at a position angle of 166°.[7] It has no physical connection to the star described above.[6][7]

References
  1. * alf Mic -- Star in double system, database entry, SIMBAD. Accessed on line September 4, 2008.
  2. NSV 13329, database entry, New Catalogue of Suspected Variable Stars, the improved version, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 4, 2008.
  3. HR 7965, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 4, 2008.
  4. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  5. 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
  6. Kaler, James B. (September 21, 2007), "Alpha Microscopii", STARS, University of Illinois, retrieved 2017-08-14.
  7. Entry 20500-3347, The Washington Double Star Catalog Archived September 8, 2008, at the Wayback Machine, United States Naval Observatory. Accessed on line September 4, 2008.
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