Overview of New Star Formation

1 -- Large Interstellar Gas and Dust Cloud is unstable and would collapse under the self pull of gravity but embedded magnetic fields of the galaxy stop the collapse and stabilize the cloud.
2 -- The magnetic field slowly diffuse out of the cloud and the cloud becomes unstable to gravitational collapse so the cloud gets smaller and more dense.
3 -- The gas cloud is very slowly rotation and as it collapses, the rate of rotation increase to conserve angular momentum. The density of the inner part increases more than the outer parts and a protostar begins to form at the center with a flat, slowly-rotating accretion disk in the plane perpendicular to the rotational axis.
4 -- As the protostar collapses and heats to thousands of degrees, it becomes visible but is usually still masked by the dust in the accretion disk. The infall of the gas and dust from the accretion disk is channeled to bipolar jets that eject material out the rotational poles of the protostar.
5 -- The central star brightens and the accretion disk is either accreted onto the star or dispersed. Planetismal bodies are accreted through out the former accretion disk.
6 -- Finally, the density and temperature of the star increases to the point the thermonuclear fusion takes place in the core of the star. Radiation pressure and stellar winds disperse remaining gas to the outer limits of the system and planets from from the planetismals.
Graphics adapted form "Deciphering the Mysteries of Stellar Origins" by Charles Lada
Sky and Telescope, May 1993, pp18-24
by Larry Bogan - Feb 2000