Photometry (astronomy)

Photometry is the field of astronomy concerned with the measurement of an astronomical object's electromagnetic radiation intensity. Usually, photometry refers to measurement over large wavelength bands of radiation, but when coupled with spectroscopy, meaning good wavelength resolution, the term spectrophotometry is used.

When the distance of the measured object can be estimated, photometry can give information about the total energy emitted by the object, its size, its temperature and other physical properties. Photometry of very distant objects is notoriously difficult, lots of hard to estimate parameters must be taken into account.

Photometry can be used as a technique to discover exoplanets. By measuring the strength of a star's light over a period of time, astronomers can examine deviations in its spectral output and determine the causes.