Poynting-Robertson effect

The Poynting-Robertson effect, also called Poynting-Robertson drag, is an effect of radiation pressure on a small particle orbiting a star that causes it to spiral slowly into the star. The radiation falls preferentially on the leading edge of the orbiting particle and acts as a drag force. For example, a dust grain one micron wide located at the position of Earth would spiral into the Sun in a period of about 3,000 years.