It has also been suggested that magnetic fields may constrain the outflowing material. The outflows carve out cavities in the surrounding interstellar medium and cause reflection nebulae to be produced. Black body radiation . The radiation emitted after a perfect absorber reaches a temperature which is higher than that of its surroundings. A perfect absorber does not reflect any electromagnetic radiation which falls upon it.
All radiation is absorbed and converted into internal energy, or heat, as it is commonly known.
It then re-radiates that heat energy as black body radiation. Perfect absorbers are often referred to as black bodies since anything black will tend to absorb radiation rather than reflect it. A close approximation is a very small hole into a constant temperature cavity, such as the human eye. The radiation emitted from stars approximates to that of a black body. This is why the colour of a star, which corresponds to its peak emission, can be used to determine its effective temperature.