What process generates the initial glow of a protostar before sustained nuclear fusion begins?

Answer

Gravitational contraction

A protostar forms as gravity causes the molecular cloud clump to contract, which increases the density and temperature, making the object glow from the heat of this contraction.

What process generates the initial glow of a protostar before sustained nuclear fusion begins?
astrophysicscelestial bodystar evolutionstellar massStar lifecycle