In astronomy, extinction refers to the reduction in observed brightness of a celestial object, such as a star or galaxy, due to the absorption and scattering of light by intervening material. This material, commonly interstellar dust or gas, is not uniform and varies greatly in composition and density throughout a given region of space. The process is wavelength-dependent, meaning that shorter wavelengths of light (such as blue light) are generally scattered more efficiently than longer wavelengths (like infrared light), causing the observed stellar spectrum to appear redder than its intrinsic color. Measurements of this extinction are crucial for determining the true luminosity and distance of cosmic sources, allowing astronomers to accurately model the composition and density of the interstellar medium.