A light curve is a graph that shows how the brightness of an object, like a star or a planet, changes over time. By measuring the light emitted or reflected by these objects, astronomers can track variations in brightness, which can reveal important information about their properties and behaviors. Light curves are particularly useful in studying phenomena such as supernovae, variable stars, and exoplanets. For example, when a planet passes in front of a star, it causes a temporary dip in brightness, which can be detected and analyzed through its light curve. This helps scientists learn more about the planet's size and orbit.