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MATERIAL FROM CLASS 18: Wednesday November 8
Color magnitude diagrams for the Pleiades and M92
The Pleiades is a young cluster, about 100 Myr old and with roughly the Sun's
abundance of elements heavier than helium. The color-magnitude diagram shows
that B stars are just beginning to leave the main sequence. The green line is
an isochrone, showing what we expect for stars of different masses that
are all 100Myr old.
M92 is a globular cluster, 12-14 billion years old and
with roughly 1% of the Sun's heavy element abundance.
The color-magnitude diagram shows that stars of roughly the Sun's mass
leaving the main sequence; more massive stars have become red giants (H burns
in a shell), horizontal branch stars (He burns in the core) and even white
dwarfs.
The green line is an isochrone, showing what we expect for stars of
different masses that are all 13Byr old.