68 Sidereal Explorations
The relative infrequency of Class B stars, already shown
in Figure 3, is well illustrated in Figure 5. For a first ap-
proximation we can consider the Class B stars in this in-
Figure 6. Class A stars of magnitudes 10.1 to 11.0 in the Taurus
region of the Henry Draper Extension. In this and the four follow-
ing diagrams the crosses indicate stars taken from the Henry
Draper Catalogue.
terval of apparent magnitude as approximately five thou-
sand light years from the Sun; brighter Class B stars are
of course generally nearer, and those fainter than the
eleventh magnitude more remote. Similarly for the other