Where does the heat of a protostar originate before fusion begins?
Answer
Ongoing process of gravitational contraction
A protostar is defined as the very dense, hot core formed during the sustained gravitational collapse of a cloud fragment. Crucially, a protostar is not yet considered a true star because its core temperature and pressure are insufficient to initiate sustained nuclear fusion. Instead, the heat observed is a direct result of energy conversion during the collapse itself. As massive amounts of matter fall inward due to gravity, gravitational potential energy is transformed into kinetic energy, which subsequently converts into thermal energy, causing the central core temperature to steadily increase.
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