What process causes interplanetary dust grains to slowly spiral inward toward the Sun?
The Poynting-Robertson effect caused by sunlight pressure
The movement and ultimate fate of the smallest interplanetary dust grains are significantly affected by the pressure exerted by the Sun's radiation and the drag force from the solar wind. A particularly crucial process governing the long-term orbital decay of these particles is the Poynting-Robertson effect. This effect dictates that the pressure exerted by sunlight on the dust grains generates a continuous drag force. Over extended periods, this drag causes the dust particles to gradually lose angular momentum, resulting in a slow, inward spiral trajectory directly toward the Sun. This continuous inward movement is responsible for feeding the zodiacal light phenomenon observed near the Sun.
