cosmic abundanceThe relative proportion of each element found in the Universe. The standard cosmic abundance is based on that of the Solar System, determined from observations of the relative line strengths in the spectrum of solar radiation, from geological surveys of the Earth, and from analysis of meteorites (see table). The solar abundance in terms of numbers of atoms gives 90.8% hydrogen, 9.1% helium, and 0.1% other elements. Abundances deduced for most stars from their spectra usually agree quite well with the standard, although old stars tend to have rather less of the heavy elements (see population I, population II) and there are a number of odd stars with abundances quite unlike the rest. The abundances deduced from the absorption and emission lines of the interstellar medium do not agree so well, principally in that there is an apparent shortage of refractory elements such as iron. It is likely that these elements are present, however, but are bound up with the cosmic dust.
cosmic abundance[′käz·mik ə′bən·dəns]
The amount of a substance believed to be present in the entire universe, relative to other substances.