A dredge-up is any one of several stages in the evolution of some stars. By definition, during a dredge-up, a convection zone extends all the way from the star's surface down to the layers of material that have undergone fusion. Consequently, the fusion products are mixed into the outer layers of the star's atmosphere, where they can be seen in stellar spectra.

Multiple stages

Note: The names of the dredge-ups are set by the evolutionary and structural state of the star in which each occurs, not by the sequence in which they occur in any one star. Some lower-mass stars experience the first and third dredge-ups in their evolution without ever having gone through the second.


  1. ^ Lambert, D.L. (1992). "Observational effects of nucleosynthesis in evolved stars". In Edmunds, Mike G.; Terlevich, Roberto J. (eds.). Elements and the Cosmos. University of Cambridge. pp. 92–109. ISBN 0-521-41475-X.
  2. ^ a b Kwok, Sun (2000). The origin and evolution of planetary nebulae. Cambridge University Press. p. 199. ISBN 0-521-62313-8.