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The K dwarf problem. The plot
shows data from our survey of nearby K dwarfs, carefully selected
in a precise range by mass (approximately 0.73 to 0.80 solar masses).
The open circles show the relative number of nearby stars with a metallicity
[Fe/H], on a logarithmic scale relative to the Sun. On this scale, the
Sun has [Fe/H]=0, while a star with 10 times less metals than the
Sun has [Fe/H]=-1. Most stars are within a factor of a few of the Sun
in their metal content. The solid curve shows the results of a model
of the processes by which metals are built up in the gas of the Milky
Way (from which these stars have been born over the last 10 billion years)
and is a good match to the data; it assumes that the initial supply of
gas has been added to by fresh gas as the Milky Way has grown. A simple
mode, in which no extra gas is included, fails to reproduce the data (and
is known as the "G-dwarf problem").
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