Final answer:
A blackbody does not reflect, scatter, or refract radiation. It's an idealized object that completely absorbs and emits radiation; hence a black T-shirt isn't a perfect blackbody as it reflects some light. Stars are often considered blackbodies due to their similar absorption and re-emission across various wavelengths.
Step-by-step explanation:
A blackbody is an idealized object in physics that does not reflect, scatter, or refract radiation but instead absorbs all the electromagnetic energy that falls onto it. Since a black T-shirt reflects some light, it cannot be considered a perfect blackbody.
Absorptive surfaces, rather than reflective surfaces, more closely model a perfect blackbody. A blackbody will radiate energy across the electromagnetic spectrum, which will peak at a certain wavelength depending on the temperature.
Astronomers refer to certain objects, like stars, as blackbodies because they absorb all incident light and re-emit energy across a spectrum of wavelengths. The term reflects the fact that in theory, if a blackbody did not emit any radiation, it would appear completely black, as it would not be reflecting any light at all. However, in reality, stars emit a wide range of colors based on their temperatures.