Planetary Nebulae and the Pregalactic Helium Abundance
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).
KeywordsRecent Work Late Stage Stellar Evolution Planetary Nebula Kinematical Property
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© International Astronomical Union 1989