Planetary Nebulae and the Pregalactic Helium Abundance

  • Walter J. Maciel
Conference paper
Part of the International Astronomical Union / Union Astronomique Internationale book series (IAUS, volume 131)


Recent work has emphasized the determination of the pregalactic helium abundance by mass Yp and the slope ΔY/ΔZ based on the chemical composition of both galactic and extragalactic H II regions (Pagel, 1987; Pagel et al., 1986).


Recent Work Late Stage Stellar Evolution Planetary Nebula Kinematical Property 
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Copyright information

© International Astronomical Union 1989

Authors and Affiliations

  • Walter J. Maciel
    • 1
  1. 1.Instituto Astronômico e Geofísico da USPSão PauloBrasil

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