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Rotation of Protostars and Stellar Disks



The July-August issue of American Scientist has an interesting article on
protostars. Unfortunately it fails to answer a question I have had for some
time. Why do protostars and their circumstellar disks rotate after
gravitational collapse from an interstellar cloud? Is it because the
gravitational collapse process is not completely radially symmetric? Is it
the rotation of the collapsing cloud which causes the flattened disk to form
from a, presumably, three-dimensional cloud? What determines the direction
of the axis of rotation? Are these rotation and flattening processes the
same processes which cause the rotation and flattening of spiral galaxies?
Since not all galaxies are flat spirals, presumably, rotation and flattening
are not obligatory after gravitational collapse.

Don Polvani
Physical Science Department
Anne Arundel Community College
Arnold, MD