A giant star has a substantially larger radius and luminosity than a main-sequence (or dwarf) star of the same surface temperature.[1] They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III.[2] The terms giant and dwarf were coined for stars of quite different luminosity despite similar temperature or spectral type by Ejnar Hertzsprung about 1905.[3]
Giant stars have radii up to a few hundred times the Sun and luminosities between 10 and a few thousand times that of the Sun. 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, but any main-sequence star is properly called a dwarf, regardless of how large and luminous it is.[4]
^Giant star, entry in Astronomy Encyclopedia, ed. Patrick Moore, New York: Oxford University Press, 2002. ISBN 0-19-521833-7.
^giant, entry in The Facts on File Dictionary of Astronomy, ed. John Daintith and William Gould, New York: Facts On File, Inc., 5th ed., 2006. ISBN 0-8160-5998-5.
^Russell, Henry Norris (1914). "Relations Between the Spectra and Other Characteristics of the Stars". Popular Astronomy. 22: 275–294. Bibcode:1914PA.....22..275R.
^Giant star, entry in Cambridge Dictionary of Astronomy, Jacqueline Mitton, Cambridge: Cambridge University Press, 2001. ISBN 0-521-80045-5.
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