When Does a Protostar Become a Main- Sequence Star

question 72

Multiple Choice

When does a protostar become a main- sequence star?

• A)at the instant that the first hydrogen fusion reactions occur in the protostar's core
• B)when it becomes luminous enough to emit thermal radiation
• C)when a piece of a molecular cloud first begins to contract into a star
• D)when the rate of hydrogen fusion becomes high enough to balance the rate at which the star radiates energy into space

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Definitions:

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Condition in which a patient is aware and awake but cannot move or communicate verbally because of complete paralysis of nearly all voluntary muscles except the eyes.

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The central trunk of the brain, continuing downwards to form the spinal cord, which controls fundamental life functions such as breathing and heart rate.

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