Giant star

From Simple English Wikipedia, the free encyclopedia
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.

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

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. The giant luminosity class is given the Roman numeral III, for bright giants it is II.

Types of giants[change | change source]

Red giants[change | change source]

These have spectral types K to M.

Yellow giants[change | change source]

These have spectral types F and G.

The Cepheid variables are yellow giants.

Blue giants[change | change source]

These have spectral types A, B, and O.

Bright giants[change | change source]

Giants nearly as bright as supergiants. They can have many spectral types.

References[change | change source]

  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