What is the defining characteristic that separates a true star from a brown dwarf?

Answer

Achieving core temperature and pressure sufficient for sustained hydrogen fusion.

The demarcation between a star and a stellar remnant like a brown dwarf is strictly whether the object can ignite and maintain the nuclear burning of hydrogen in its core, which requires specific critical core conditions.

What is the defining characteristic that separates a true star from a brown dwarf?

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How Do Stars Form? - YouTube

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