What structure surrounds a protostar and contributes energy via infalling matter?

Answer

An accretion disk

A protostar is almost always surrounded by an accretion disk—a flattened swirl of gas and dust—where material spirals inward, gaining speed before slamming into the surface and converting kinetic energy into thermal energy.

What structure surrounds a protostar and contributes energy via infalling matter?
protostarstar formationastrophysicsenergy generation