⏾ Concept Map

K-Type ○ Entries

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K-Type ○｜Definition｜1st｜20260908165233-00-⌔

Stellar classification - Wikipedia#Class_K

Class K

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K-type stars are orangish stars that are slightly cooler than the Sun. They make up about 12% of the main-sequence stars in the solar neighborhood.12 There are also giant K-type stars, which range from hypergiants like RW Cephei, to giants and supergiants, such as Arcturus, whereas orange dwarfs, like Toliman, are main-sequence stars.

They have extremely weak hydrogen lines, if those are present at all, and mostly neutral metals (Mn I, Fe I, Si I). By late K, molecular bands of titanium oxide become present. Mainstream theories (those rooted in lower harmful radioactivity and star longevity) would thus suggest such stars have the optimal chances of heavily evolved life developing on orbiting planets (if such life is directly analogous to Earth’s) due to a broad habitable zone yet much lower harmful periods of emission compared to those with the broadest such zones.34

Example spectral standards:5

  • K0V – Sigma Draconis
  • K0III – Pollux
  • K0III – Epsilon Cygni
  • K2V – Epsilon Eridani
  • K2III – Kappa Ophiuchi
  • K3III – Rho Boötis
  • K5V – 61 Cygni A
  • K5III – Gamma Draconis

Printed 2026-09-08.

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Footnotes

  1. These proportions are fractions of stars brighter than absolute magnitude 16; lowering this limit will render earlier types even rarer, whereas generally adding only to the M class. The proportions are calculated ignoring the value of 800 in the total column since the actual numbers add up to 824. ↩

  2. Ledrew, Glenn (February 2001). “The Real Starry Sky”. Journal of the Royal Astronomical Society of Canada. 95: 32. Bibcode:2001JRASC..95…32L. ↩

  3. “On a cosmological timescale, The Earth’s period of habitability is nearly over | International Space Fellowship”. Spacefellowship.com. Retrieved 22 May 2012. ↩

  4. ""Goldilocks”Stars May Be”Just Right”for Finding Habitable Worlds”. NASA.com. 7 March 2019. Retrieved 26 August 2021. ↩

  5. Garrison, R. F. (1994). “A Hierarchy of Standards for the MK Process” (PDF). In Corbally, C. J.; Gray, R. O.; Garrison, R. F. (eds.). The MK Process at 50 Years: A Powerful Tool for Astrophysical Insight. Astronomical Society of the Pacific conference series. Vol. 60. San Francisco: Astronomical Society of the Pacific. pp. 3–14. ISBN 978-1-58381-396-6. OCLC 680222523. ↩

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