What must happen to a collapsing cloud of gas and dust, now a protostar, to ignite sustained hydrogen fusion?

Answer

The core must reach the critical temperature, around 15 million degrees Celsius for a Sun-like star

A collapsing cloud continues to heat up until its core reaches the critical temperature required to ignite sustained hydrogen fusion, cited as around 15 million degrees Celsius for a star like our Sun.

What must happen to a collapsing cloud of gas and dust, now a protostar, to ignite sustained hydrogen fusion?
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