Collapse of a Protostar

Stars form from the collapse of “dense” (~1000 atoms/cm3) molecular clouds
- Cloud has few 100,000 or a million solar masses of material
- Temperature ~ 10K (COLD!)
Why do they collapse? GRAVITY
- Sitting in gravitational equilibrium, compressed slightly, gravity takes over!
- Converts gravitational potential energy to THERMAL energy (infalling material heats up)
- Cloud fragments as it collapses – each fragment becomes a PROTOSTAR, emitting radiation because it is hot

Stars form from the collapse of “dense” (~1000 atoms/cm3) molecular clouds