Planetology
In planetology, a light curve can be used to estimate the rotation period of a minor planet, moon, or comet nucleus. From the Earth there is often no way to resolve a small object in our Solar System, even in the most powerful of telescopes, since the apparent angular size of the object is smaller than one pixel in the detector. Thus, astronomers measure the amount of light produced by an object as a function of time (the light curve). The time separation of peaks in the light curve gives an estimate of the rotational period of the object. The difference between the maximum and minimum brightnesses (the amplitude of the light curve) can be due to the shape of the object, or to bright and dark areas on its surface. For example, an asymmetrical asteroid's light curve generally has more pronounced peaks, while a more spherical object's light curve will be flatter. When the light curve covers an extended period of time, it is called a secular light curve.
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