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Revision as of 14:52, 11 June 2002 by Bryan Derksen (talk | contribs) (links)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)A red giant is a large star of spectral class K or M which is off the main sequence. They are believed to be stars of solar mass or higher which have started helium fusion which causes the outer layers of the star to massively expand. This expansion is consistently predicted by numerical simulations of stellar evolution, yet astronomers find it difficult to state in words why it happens.