Light ElementsThe light elements 2H, 3He, 4He, and 7Li are expected to be produced during the era of primordial nucleosynthesis and then further processed by stars over many generations. Observations of the light elements can in principle be used to constrain models of stellar and Galactic evolution and cosmology.
Below are results from observations of the 3He+ hyperfine transition at 3.5 cm toward Galactic HII regions and planetary nebula. The solid points and crosses are Galactic HII region 3He/H abundance ratios representing the present day abundances. The triangle is the 3He/H abundance ratio toward the PNe NGC3242. The solid line indicates the primordial 3He/H abundance predicted by Big Bang nucleosynthesis assuming the WMAP baryon-to-photon ratio. (See Balser et al. 2006, ApJ, 640, 360; Bania et al. 2002, Nature, 415, 54)
Modified on Friday, 17-Nov-2006 15:13:46 EST