Eight stages to the formation of a low mass star like our sun.

The Stages:

1. The Cloud: 10 pc, 104 Msun , 108 yr
(supersonic)turbulence, magnetic (ambipolar) diffusion
2. The Clumps: 2-5 pc, 103 Msun, 107 yr
magnetic energy, rotational braking
3. Cores: 0.1 pc, 1 Msun
thermal support
4. Collapse:
isothermal free-fall phase, 3 105 yr
adiabatic phase, optically thick
second collapse phase: dissociation of H2
5. Class 0: 104 yr
mass in envelope
accretion onto small core
molecular jets and shocks
6. Class 1: 105 yr
embedded IR source
disk, outflow
7. Class 2: 106 yr
IR+UV excesses
atomic jets
8. Class 3: 107 yr
naked, surface activity
starspots, giant flares

Last Revised: 2009 November 2nd