Page 6, Star Formation & Structure: [Previous Page] [Next Page] [Class Home Page] Text Pages 286-287

What we really see in nature during the collapse of the molecular cloud is a bit more complicated than outlined previously. The most important issue to be discussed is that of Angular Momentum.




Angular Momentum. You know it in day-to-day experiences: It's difficult to walk to the center of a merry-go-round ONLY when its spinning. All material from the molecular cloud can't just drop to the center because most of it will have at least some component of rotation relative to the center of the cloud. As it moves in, the rotation speeds up, inhibiting further infall.




Instead of falling directly onto the protostar, most of the material from the molecular cloud builds up in an extended disk, first. The material in the disk heats up due to collisions, and thereby converts its ANGULAR MOMENTUM to thermal energy. This allows the material in the disk to move further and further in. We directly see these disks (shown in green light) around very young stars called T Tauri stars. These T Tauri stars also show bipolar flows and jets (perpendicular to the disks, seen here in red light). All of these observed phenomenon are predicted from the collapse formation of stars.




These jets, or bipolar flows, can contain bright knots called Herbig-Haro objects, and are seen to extend to ENORMOUS distances from the central star (seen to the left below).


A Real HR Diagram of a Young Cluster Young stars still lie in a region cooler and more luminous than Main sequence stars. Newly formed proto-stars are still heating up and contracting.