Editing Poynting–Robertson effect (section)

{{Short description|Process whereby solar radiation causes orbiting dust grains to lose angular momentum}}
The '''Poynting–Robertson effect''', also known as '''Poynting–Robertson drag''', named after [[John Henry Poynting]] and [[Howard P. Robertson]], is a process by which [[solar radiation]] causes a dust grain orbiting a star to lose [[angular momentum]] relative to its orbit around the star. This is related to [[radiation pressure]] tangential to the grain's motion.

This causes dust that is small enough to be affected by this drag, but too large to be blown away from the star by radiation pressure, to spiral slowly into the star. In the [[Solar System]], this affects dust grains from about {{Val|1|ul=um}} to {{val|1|ul=mm}} in diameter. Larger dust is likely to collide with another object long before such drag can have an effect.

Poynting initially gave a description of the effect in 1903 based on the [[luminiferous aether]] theory, which was superseded by the [[theory of relativity|theories of relativity]] in 1905–1915. In 1937 Robertson described the effect in terms of [[general relativity]].