Poynting–Robertson effect

The gradual loss of orbital energy and angular momentum by a particle absorbing and re-emitting starlight, causing it to spiral toward its star.

Radiation pressure: Force exerted on matter when photons transfer momentum through absorption, reflection, or scattering. It supplies the photon momentum whose direction is aberrated by the dust’s orbital motion.
Keplerian orbit: An ideal orbit governed by Newtonian gravity around a central mass. The effect slowly modifies the nearly Keplerian paths followed by circumstellar dust.
Interplanetary dust cloud: The diffuse population of microscopic solid particles distributed throughout a planetary system. Solar Poynting–Robertson drag causes small grains in this cloud to drift toward the Sun.
Radiation pressure blowout: The ejection of small grains from a stellar system when radiation pressure overcomes stellar gravity. Blowout expels grains, whereas Poynting–Robertson drag gradually draws bound grains inward.
Relativistic aberration: The apparent change in a light source’s direction caused by relative motion between source and observer. The particle’s motion makes incoming stellar radiation appear slightly displaced from the radial direction.
Photon momentum: Momentum carried by a photon, proportional to its energy and inversely proportional to the speed of light. Absorbed and emitted photons transfer momentum to the orbiting particle.
Zodiacal light: Faint sunlight scattered by interplanetary dust, visible along the ecliptic after twilight or before dawn. The dust producing this glow is continually redistributed by radiation forces.
Yarkovsky effect: A thermal recoil force that changes an asteroid’s orbit because its rotating surface emits heat unevenly. Both effects arise from photon recoil, but Yarkovsky drift depends on delayed thermal emission and rotation.
Radiative transfer: The physical description of how radiation is emitted, absorbed, scattered, and transported through matter. Absorption and re-emission determine how photon momentum becomes a drag force.
Optical absorption: The transfer of electromagnetic energy from radiation to matter. Absorption is the first step in the photon-momentum exchange that produces the effect.

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