The brightness of an astronomical object, expressed on a unique numerical scale. The stellar magnitude scale is logarithmic and is inverted in that fainter objects have numerically larger magnitudes. The term “magnitude” in this context refers to brightness only and has nothing to do with the size or other quantities. Although used primarily for stars, the stellar magnitude scale can also be used to express the brightness of the Sun, planets, asteroids, comets, nebulae, galaxies, and even background radiation.