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G

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—G stars, which includes the Sun,[1] have prominent spectral lines H and K of Ca II, which are most pronounced at G2. They have even weaker hydrogen lines than F, but along with the ionized metals, they have neutral metals. There is a prominent spike in the G band of CH molecules. Class G main-sequence stars make up about 7.5%, nearly one in thirteen, of the main-sequence stars in the solar neighborhood.[2]

G is host to the "Yellow Evolutionary Void".[3] Supergiant stars often swing between O or B (blue) and K or M (red). While they do this, they do not stay for long in the yellow supergiant G class, as this is an extremely unstable place for a supergiant to be.

Spectral standards:[4]
  • G0V – Beta Canum Venaticorum
  • G0IV – Eta Boötis
  • G0Ib – Beta Aquarii
  • G2V – Sun
  • G5V – Kappa Ceti
  • G5IV – Mu Herculis
  • G5Ib – 9 Pegasi
  • G8V – 61 Ursae Majoris
  • G8IV – Beta Aquilae
  • G8IIIa – Kappa Geminorum
  • G8IIIab – Epsilon Virginis
  • G8Ib – Epsilon Geminorum

See also

References

  1. ↑ Phillips, Kenneth J. H. (1995). Guide to the Sun. Cambridge University Press. pp. 47–53. ISBN 978-0-521-39788-9. 
  2. ↑ Ledrew, Glenn (February 2001). "The Real Starry Sky". Journal of the Royal Astronomical Society of Canada 95: 32. Bibcode: 2001JRASC..95...32L. 
  3. ↑ Nieuwenhuijzen, H.; De Jager, C. (2000). "Checking the yellow evolutionary void. Three evolutionary critical Hypergiants: HD 33579, HR 8752 & IRC +10420". Astronomy and Astrophysics 353: 163. Bibcode: 2000A&A...353..163N. 
  4. ↑ Garrison, R. F. (1994). "A Hierarchy of Standards for the MK Process". Astronomical Society of the Pacific 60: 3. Bibcode: 1994ASPC...60....3G.