A comet is an object that looks rather large (not simply a dot, like the stars), and kind of cloudy and blurred. It moves daily with the stars, but changes its position among them fairly rapidly (as compared, say, to planets). It grows in brightness over a period of weeks or months, reaches a peak, then subsides and disappears. It may reappear after several or many years, or it may never reappear. The brightest comets can be seen in the day time.