Why does an intensely luminous protostar shine brightly mainly in infrared light?

Answer

Infalling dust and gas traps heat, re-radiating it at longer wavelengths

The surrounding layer of obscuring infalling dust and gas traps the heat generated near the core, causing the system to re-radiate this energy primarily at longer, infrared wavelengths.

Why does an intensely luminous protostar shine brightly mainly in infrared light?
star formationastrophysicsprotostarsstellar physicsheat generation