•Envelope
of red giant very loosely held
–Star
is so big, gravity very weak at the surface
•Degenerate
core makes nuclear “thermostat” sluggish
–Core
doesn’t quickly expand and cool when fusion is to fast
–Energy
can be generated in “thermal pulses”
•Low
temperature opaque envelope can also “oscillate”
–Energy
is transmitted in “pulses” as envelope expands and contracts
–Main
cause of “Variable Stars”
•Some Red Giants
have very strong stellar winds
ejecting envelopes,
forming “Planetary Nebulae”
•PN called this because some looked like planets in poor telescopes
•PN don’t have anything to do with formation of
planets