Definition of "protostar" [protostar]

• A collection of gas and dust in space with high temperature that usually grows to the point of beginning nuclear fusion and becoming a star. (noun)

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• "Since then, stars have formed by the collapse of small, dense core regions in large, cold protostar, which is hot and bright because of energy generated by gravitational contraction."
• "Another unsurprising confirmation of stellar formation models is that forming cores in the nebula are notably warmer when they've reached the density sufficient to create fusion in the core and have an embedded protostar."
• "With this new movie, we can see changes over just a few months as gas clumps swarm around this young protostar, added Smithsonian astronomer and co-author Ciriaco Goddi."