Astronomy:Mu Cassiopeiae

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Mu Cassiopeiae (μ Cassiopeiae, abbreviated μ Cas) is a binary star system in the constellation Cassiopeia. This system shares the name Marfak /ˈmɑːrfæk/ with Theta Cassiopeiae, and the name was from Al Marfik or Al Mirfaq (المرفق), meaning "the elbow".[1]

Mu Cassiopeiae is given as a standard star for the spectral class G5Vb,[2] although it is frequently described as a subdwarf, meaning it has a luminosity below that expected for a G5 main sequence star.[3]

There are five visible companions to Mu Cassiopeiae listed in the Washington Double Star Catalog. All are distant background objects fainter than 11th magnitude. The brightest of these is catalogued as component B, but the very high proper motion of Mu Cassiopeiae has caused it to almost double its distance from B. There are now two other stars brighter than magnitude 10 that are closer to Mu Cassiopeiae, although they are also background objects.[4] The companions C and D are separated from each-other by four arc seconds and form a binary system about 4,000 ly away.[5][6] Mu Cassiopeiae itself is known as an astrometric binary, a star that is observed to oscillate due to the gravitational influence of an unseen companion, and that companion has now been resolved.[7]

In 1961 the close binary nature of this system was discovered by Nicholas E. Wagman at the Allegheny Observatory.[8] Since then the orbital elements of the two stars have been fairly well established. The two stars are separated by a semimajor axis of 7.61 AUs with distance range of 3.3-11.9 AUs.[9] In 1966, the individual components were first resolved by the American astronomer Peter A. Wehinger using the 84-inch reflector at the Kitt Peak National Observatory, allowing an initial estimate of separate masses.[10] The companion is over six magnitudes (330 times) fainter than the primary star, and it is presumed to be a red dwarf, a class M main sequence or subdwarf star.[7]

Compared to other nearby stars, this pair are moving at a relatively high velocity of 167 km/s through the Milky Way galaxy. They are low metal, Population II stars that are thought to have formed before the galactic disk first appeared.

This star will move into the constellation Perseus around 5200 AD.[11]

References

  1. Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 148, ISBN 978-0-486-21079-7, https://archive.org/details/starnamestheirlo00alle/page/148, retrieved 2010-12-12 
  2. Keenan, Philip C; McNeil, Raymond C (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series 71: 245. doi:10.1086/191373. Bibcode1989ApJS...71..245K. 
  3. Boyajian, Tabetha S. et al. (August 2008), "Angular Diameters of the G Subdwarf μ Cassiopeiae A and the K Dwarfs σ Draconis and HR 511 from Interferometric Measurements with the CHARA Array", The Astrophysical Journal 683 (1): 424–432, doi:10.1086/589554, Bibcode2008ApJ...683..424B 
  4. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466. doi:10.1086/323920. Bibcode2001AJ....122.3466M. 
  5. Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  6. Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  7. 7.0 7.1 Drummond, Jack D; Christou, Julian C; Fugate, Robert Q (1995). "Full Adaptive Optics Images of ADS 9731 and MU Cassiopeiae: Orbits and Masses". Astrophysical Journal 450: 380. doi:10.1086/176148. Bibcode1995ApJ...450..380D. 
  8. Lippincott, S. L.; Wyckoff, S. (September 1964), "Parallax and orbital motion of the astrometric binary mu Cassiopeiae from photographs taken with the 24-inch Sproul refractor", Astronomical Journal 69: 471–474, doi:10.1086/109301, Bibcode1964AJ.....69..471L 
  9. Professor Jim Kaler, Mu Cassiopeiae, http://stars.astro.illinois.edu/sow/marfakw.html, retrieved 2019-02-13 
  10. Wehinger, Peter A.; Wyckoff, Susan (February 1966), "Preliminary Mass Determination of μ Cas", Astronomical Journal 71: 185, doi:10.1086/110028, Bibcode1966AJ.....71Q.185W, http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1966AJ.....71Q.185W&link_type=ARTICLE&db_key=AST&high= 
  11. Patrick Moore; Robin Rees (2011), Patrick Moore's Data Book of Astronomy, Cambridge University Press, https://books.google.com/books?id=2FNfjWKBZx8C 

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External links

https://en.wikipedia.org/wiki/Mu Cassiopeiae was the original source. Read more.