摘要
Planetary nebulae are the progenetors of white dwarfs in the final evolution stage of stars with intermediate initial mass ( 1M_⊙【M_*【9M_⊙). The planetary nebulae can be devided into different groups according to the spectral type of their core stars. One of these groups, in which the spectrum is dominated by the carbon lines of different levels of ionization, is similar to the carbon-rich Wolf-Rayet stars. According to Van der Hucht
