A Color-Magnitude Diagram for Late-Type Stars Near the Sun.

A color-magnitude diagram for late-type stars in the solar neighborhood is derived from measures of the widths of the bright H and K reversals in the spectra of stars for which photoelectric values of B - V are available. The diagram is filled out by the inclusion of stars with trigonometric parallaxes >0'oso. From the plotted points it is possible to delineate with fair accuracy the limiting evolutionary track for the oldest galactic stars and to estimate the location of the break-off point from the main sequence. The corresponding age of the galaxy is about lOiS years, but this estimate is subject to improvement with the addition of further observations.