A light curve records brightness over time. It can tell astronomers about the size, shape, and rotation of an object. This light curve shows ‘Oumuamua’s brightness during three days in October 2017; each color depicts measurements taken in a different filter, which views only specific wavelengths of visible or infrared light. The large dips in brightness tell astronomers that ‘Oumuamua is long but skinny, more like a cylinder than a ball. The dotted line represents the light curve of a model object that is 10 times longer than it is wide.