Stellar carbon cycle

Figure 2.3 Dust production and gas mass return rate by different stellar types in solar masses per year and kpc-2 in the galaxy at the solar cycle. Stars produce mainly silicate or carbon dust only in some cases is a different kind of dust material formed, probably iron or some iron alloy (peculiar dust). Many additional dust components with much smaller abundance are formed in most cases (Data from Tielens 1999 Zhukovska el al. 2008). Abbreviations of stellar types AGB = asymptotic giant branch stars of spectral types M, S, or C OB = massive stars of spectral types O and B on or close to the main sequence RGB = massive stars on the red giant branch LBV = luminous blue variables WCL = Wolf-Rayet stars from the lower temperature range Novae = mass ejecta from novae SN = mass ejecta from supemovae.

When the stellar core has been depleted of carbon and oxygen and is rich in silicon, the silicon-burning phase can begin, and silicon is converted to sulfur, argon, and other heavier elements. If contraction can raise the temperature of the interior to about 3 billion degrees, then the so-called equilibrium phase of the star s life cycle begins, and elements close to iron are formed. Iron is the most stable nucleus of all as noted, if a star were to burn to its end, it would become a ball of iron. 

CNO cycle CNO = carbon, nitrogen, and oxygen refers to the stellar nuclear fusion sequence in which nitrogen and oxygen nuclei are created from carbon nuclei. 

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