G-dwarf problemThe observed lack of metal-poor stars in our Galaxy. There are expected to be some stars that formed early in the life of our Galaxy and, if of less than one solar mass (i.e. dwarf stars of spectral type G), have not yet evolved away from the main sequence. There should thus be a population of low-mass stars that display the very low metal abundances expected to be typical of the conditions at the time of the formation of the Galaxy. Subsequent generations of more massive population I stars have since enriched the environment. The lack of observed stars of the expected metallicity may be understood if the early initial mass function (see stellar mass) was radically different, consisting of only massive stars, or by invoking a hypothetical population III whose very rapid evolution enriched the Galaxy as it formed.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006