A brief review of some recent results on planetary nebulae research is presented. The following results are stressed: a) Type I PN form a homogeneous group with initial masses in the 2.4 to 8 M@ range; b) recent observations of NGC 2346, NGC 6302 and CRL 618 are discussed which are in agreement with the hypothesis of the production of Type I PN by at least two stages of mass loss, with the last one being confined by a toroid produced by the previous one; c) Type I PN seem to be 0 deficient which would imply that most of their excess N is of secondary origin, but produced from 0 and not from C; d) Type IV PN, halo population, present freshly made C in their envelopes, producing it at a rate 1.5 < AY/ Ax < 7, therefore from their excess C alone it is not possible to accurately determine their excess helium; e) PN are responsible for most of the C production present in the interstellar medium of the solar vicinity.
Revista Mexicana de Astronomia y Astrofisica, vol. 10
- Pub Date:
- March 1985