Figure adopted from Reid (2000).
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Masses > 0.08 MSun:
Core temperatures during contraction increase enough to maintain PPI and hydrostatic equilibrium
- True stars - Type M (red dwarfs)
0.06 MSun < Masses < 0.08 MSun:
Core temperatures initially high enough for lithium burning (Li7 + p -> 2 He4)
- Partial degeneracy absorbs energy from contraction then fusion, eventually causes downturn below critical temperature
- "Transition Objects" - Late M, Early L
Masses < 0.06 MSun
Core temperatures never achieved lithium fusion.
- Because dwarfs are fully convective, Li 6707å visible in their spectra - "the lithium test".
- Late L, All T
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