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A

Stars classified under the
Morgan-Keenan (MK) system use the letters
O, B, A, F, G, K, and M,
a sequence used to identify the hottest (O type) to the coolest (M type) stars


Class—A stars are among the more common naked eye stars, and are white or bluish-white. They have strong hydrogen lines, at a maximum by A0, and also lines of ionized metals (Fe II, Mg II, Si II) at a maximum at A5. The presence of Ca II lines is notably strengthening by this point. About 1 in 160 (0.625%) of the main-sequence stars in the solar neighborhood are A-type stars.[1][2]

Spectral standards:[3]
  • A0Van – Gamma Ursae Majoris
  • A0Va – Vega
  • A0Ib – Eta Leonis
  • A0Ia – HD 21389
  • A2Ia – Deneb
  • A3Va – Fomalhaut

See also

References

  1. ↑ Ledrew, Glenn (February 2001). "The Real Starry Sky". Journal of the Royal Astronomical Society of Canada 95: 32. Bibcode: 2001JRASC..95...32L. 
  2. ↑ "SIMBAD Object query : CCDM J02319+8915". SIMBAD. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=CCDM+J02319%2B8915&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id. Retrieved 10 June 2010. 
  3. ↑ Garrison, R. F. (1994). "A Hierarchy of Standards for the MK Process". Astronomical Society of the Pacific 60: 3. Bibcode: 1994ASPC...60....3G.