Often, a bright planet that is visible over the horizon will be mistaken for a star. Some believe they can tell the difference between a star and a planet because stars twinkle, or scintillate, and planets do not. In actuality however, both will twinkle because any light that passes through our atmosphere, whether it be reflected from a planet or generated by a star, will be interfered with by the atmospheric elements. This month's column sheds light on this "scintillating" subject and engages students in a research activity that revolves around the question: Is Pluto a planet?