Wikipedia

Alpha Microscopii

Alpha Microscopii (α Microscopii) is a star in the southern constellation of Microscopium.[13] It is visible to the naked eye with an apparent visual magnitude of 4.89.[2] Based upon an annual parallax shift of 8.2508 mas as seen from the Earth, it is located 395 light years from the Sun, give or take 7 light years. The star is moving nearer to the Sun with a heliocentric radial velocity of −15 km/s[6]

α Microscopii
Location of α Microscopii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Microscopium
Right ascension 20h 49m 58.0810s[1]
Declination −33° 46′ 46.9344″[1]
Apparent magnitude (V) 4.89±0.01[2]
Characteristics
Spectral type G7 III[3] or G8 III[4]
U−B color index +0.73[5]
B−V color index +1.00[5]
Astrometry
Radial velocity (Rv)−14.50±0.09[6] km/s
Proper motion (μ) RA: +15.057 mas/yr[1]
Dec.: −23.524 mas/yr[1]
Parallax (π)8.2508 ± 0.1563 mas[7]
Distance395 ± 7 ly
(121 ± 2 pc)
Absolute magnitude (MV)−0.45 ± 0.20[8]
Details[9]
Mass3.19±0.32 M☉
Radius18.41±1.38 R☉
Luminosity173±25 L☉
Surface gravity (log g)2.27±0.11 cgs
Temperature4,881±43 K
Metallicity [Fe/H]−0.06±0.04 dex
Rotational velocity (v sin i)2.6±2[10] km/s
Age400[11] Myr
Other designations
α Mic, 27 G. Microscopii, CD−34°14660, CPD−34°8799, GC 29026, HD 198232, HIP 102831, HR 7965, SAO 212472, WDS 20500-3347A[12][13]
Database references
SIMBADdata

This is an evolved giant star of type G with a stellar classification of either G7 III[3] or G8 III[4] depending on the source. At the age of 400 million years, it has an estimated 3.19 times the mass of the Sun and has expanded to 18.4 times the Sun's radius.[9] The star is radiating 173 times the Sun's luminosity from its expanded photosphere at an effective temperature of 4,881 K, giving a yellow hue.[9]

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°.[14] It has no physical connection to the star described above.[15] As for Alpha Microscopii, it was found to be a probable spectroscopic binary in 2014.[10]

References

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  1. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
  3. ^ a b Hoffleit, Dorrit; Shapley, Harlow (1937). "Spectroscopic absolute magnitudes of three hundred and seventy southern stars". Annals of Harvard College Observatory. 105 (3): 45–68. Bibcode:1937AnHar.105...45H.
  4. ^ a b Houk, N. (1982). Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0. Bibcode:1982mcts.book.....H.
  5. ^ a b Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
  6. ^ a b Jofré, E.; Petrucci, R.; Saffe, C.; Saker, L.; Artur de la Villarmois, E.; Chavero, C.; Gómez, M.; Mauas, P. J. D. (26 January 2015). "Stellar parameters and chemical abundances of 223 evolved stars with and without planets". Astronomy & Astrophysics. 574: A50. arXiv:1410.6422. Bibcode:2015A&A...574A..50J. doi:10.1051/0004-6361/201424474. eISSN 1432-0746. ISSN 0004-6361.
  7. ^ 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.
  8. ^ 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.
  9. ^ a b c Ottoni, G.; Udry, S.; Ségransan, D.; Buldgen, G.; Lovis, C.; Eggenberger, P.; Pezzotti, C.; Adibekyan, V.; Marmier, M.; Mayor, M.; Santos, N. C.; Sousa, S. G.; Lagarde, N.; Charbonnel, C. (January 2022). "CORALIE radial-velocity search for companions around evolved stars (CASCADES): I. Sample definition and first results: Three new planets orbiting giant stars". Astronomy & Astrophysics. 657: A87. arXiv:2201.01528. Bibcode:2022A&A...657A..87O. doi:10.1051/0004-6361/202040078. ISSN 0004-6361.
  10. ^ a b De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars: V. Southern stars⋆⋆⋆". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. ISSN 0004-6361.
  11. ^ Demarque, Pierre; Woo, Jong-Hak; Kim, Yong-Cheol; Yi, Sukyoung K. (December 2004). "Y 2 Isochrones with an Improved Core Overshoot Treatment". The Astrophysical Journal Supplement Series. 155 (2): 667–674. arXiv:astro-ph/0409024. Bibcode:2004ApJS..155..667D. doi:10.1086/424966. ISSN 1538-4357.
  12. ^ Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
  13. ^ a b * alf Mic -- Star in double system, database entry, SIMBAD. Accessed on line September 4, 2008.
  14. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. ISSN 0004-6256.
  15. ^ Kaler, James B. (September 21, 2007). "Alpha Microscopii". STARS. University of Illinois. Retrieved 2017-08-14.
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