Photometry is a branch of astronomy that involves measuring the intensity of light emitted or reflected by celestial objects. This can include measurements of the brightness or luminosity of stars, galaxies, and other astronomical bodies across different wavelengths of light. Photometry is important in determining the physical properties of celestial objects, such as their temperature, mass, and distance from Earth. It is also used to study the variability of objects, such as variable stars or active galactic nuclei. Techniques used in photometry include imaging, spectroscopy, and polarimetry.