Final answer:
Photometry is the measurement of the brightness of celestial objects using instruments like telescopes and photometers. It helps astronomers gather information about properties such as composition, temperature, and distance.
Step-by-step explanation:
Photometry is the measurement of the brightness of celestial objects. It is a technique used by astronomers to study stars and other celestial bodies. The process involves measuring the amount of light emitted or reflected by an object using instruments such as telescopes and photometers. By analyzing and comparing the brightness of different objects, astronomers can gather valuable information about their properties, such as their composition, temperature, and distance.