Stellar magnitude is measure of the brightness of a star or other celestial body.
The brighter the object, the lower the number assigned as a magnitude. In ancient times, stars were ranked in six magnitude classes, the first magnitude class containing the brightest stars. In 1850 the English astronomer Norman Robert Pogson proposed the system presently in use. Thus, a difference of five magnitudes corresponds to a brightness ratio of 100 to 1. After standardization and assignment of the zero point, the brightest class was found to contain too great a range of luminosities, and negative magnitudes were introduced to spread the range.