As a cloud collapses to form a protostar, the forces of...

Name: Problem 26, Chapter 15: 21st Century Astronomy
Uploaded: 2020-07-15T17:54:54-08:00
Duration: 2 min 40 s
Channel: Sarah Mccrumb
Description: As a cloud collapses to form a protostar, the forces of gravity felt by all parts of the cloud (which follow an inverse square law become stronger and stronger. One might argue that under these conditions, the cloud should keep collapsing until it becomes a single massive object. Why doesn't this happen?

As a cloud collapses to form a protostar, the forces of gravity felt by all parts of the cloud (which follow an inverse square law become stronger and stronger. One might argue that under these conditions, the cloud should keep collapsing until it becomes a single massive object. Why doesn't this happen?

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Key Concepts

Hydrostatic Equilibrium

In star formation, hydrostatic equilibrium refers to the balance between the inward pull of gravity and the outward pressure forces (such as thermal pressure) generated by the gas and radiation. When a segment of a collapsing molecular cloud reaches this balance, it stops contracting further in that region, effectively resisting a complete collapse into a single massive object.

Fragmentation of Collapsing Clouds

As a molecular cloud collapses under gravity, local density fluctuations can lead to different regions collapsing at different rates. This process, known as fragmentation, results in the cloud breaking up into multiple smaller cores rather than collapsing into one monolithic object. Fragmentation is a key process in star formation, as it allows clusters of stars to form instead of a single massive star.

Angular Momentum Conservation

During the collapse of a cloud, any small initial rotation is amplified due to the conservation of angular momentum. This rotational motion acts to flatten the collapsing material into a disk and can lead to the development of multiple centers of mass. The resulting centrifugal forces oppose the complete collapse along the rotational axis, further contributing to the formation of separate stellar objects rather than a single massive body.

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