Giant star

A giant star is a star with much larger radius and luminosity than a main-sequence star of the same surface temperature.[2][3]

Hertzsprung–Russell diagram.[1] with 23,000 stars plotted. Most stars are on the diagonal, going from the upper-left (hot and bright) to the lower-right (cooler and less bright), called the main sequence. Above and to the right are the giants. The Sun is on the main sequence, not a giant.
An HR diagram with the instability strip of variable stars highlighted.

Giant stars are up to a few hundred times the diameter of the Sun and between 10 and a few thousand times brighter than the Sun. They don't last as long as most main sequence stars. Stars still more luminous than giants are referred to as supergiants and hypergiants.

A hot, luminous main-sequence star may also be referred to as a giant.[4]

There are a wide range of giant class stars, and sub-divisions are often used to identify particular types. Astronomers use such terms as: sub-giants, bright giants, red giants, yellow giants and blue giants.

References
  1. Richard Powell with permission.
  2. Giant star. In Astronomy Encyclopedia, ed. Patrick Moore, New York: Oxford University Press, 2002. ISBN 0-19-521833-7
  3. Giant. In The Facts on File Dictionary of Astronomy, ed. John Daintith and William Gould. 5th ed, New York: Facts On File, 2006. ISBN 0-8160-5998-5
  4. Giant star. In Cambridge Dictionary of Astronomy, Mitton, Jacqueline. Cambridge University Press 2001. ISBN 0-521-80045-5
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