Final answer:
Protostars shine brightest in the infrared spectrum, as the dusty envelope surrounding them during formation allows infrared radiation to pass through, making it detectable by astronomical instruments.
Step-by-step explanation:
Protostars are observed to shine brightest in the infrared spectrum. This is because during the early stages of formation, a protostar is surrounded by a dusty envelope that blocks visible light. However, infrared radiation can penetrate this dust, making it possible for us to detect the glowing protostar. Additionally, the very cool temperatures of these objects also mean they emit most strongly in the infrared. Instruments designed to operate at infrared wavelengths are essential for astronomers to study these early stages of star formation.