by Sa Ji Tario » Sun Sep 03, 2023 2:53 pm
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Poynting–Robertson effect
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The Poynting-Robertson effect is a process by which interplanetary dust particles are slowly spiraled toward the Sun by solar radiation. This is because the orbital motion of the dust grains is counteracted by the radiation pressure component tangent to the motion.
Interpretation
The effect can be interpreted in two ways, depending on the reference system from which it is described.
From the perspective of the dust grain, the Sun's radiation appears to come from a slightly tilted angle toward the direction of motion (see light aberration); therefore, the absorption of this incident radiation by the grain (in other words, the transfer of momentum from it to it) results in a net force that opposes its orbital motion. This action is slow, since the angle of aberration is very small (solar radiation moves at the speed of light and the particle moves at a much lower speed).
From the perspective of the Sun (reference system at rest), the dust grain absorbs all the sunlight it receives from the radial direction, perpendicular to its movement and, therefore, its angular momentum does not change; however, the absorbing photons acquire mass (mass-energy equivalence), so to conserve angular momentum, their distance from the Sun must decrease.
Considering the re-emission of the energy absorbed by the grain, note that in the first case (seen from the grain) said re-emission is isotropic (same in all directions), and does not affect the movement. But seen from the Sun, the re-emission is anisotropic and the photons "carry" the angular momentum of the particle, a loss that must be compensated by approaching the Sun.
The action described is very slow, although its effect is cumulative over time: if a particle of a few micrometers (μm) is located at a distance from the Sun equivalent to Earth's orbit (one astronomical unit), it will need about seven thousand years to complete. the spiral towards the Sun. In very small particles (on the order of a fraction of μm or less) the radiation pressure of the Sun predominates and they have, therefore, outward motions. The Poynting-Robertson effect is also more intense near the Sun and tends to reduce the eccentricity of elliptical orbits.
References
JH Poynting (1903). Radiation in the Solar System: its effect on temperature and its pressure on small bodies. Philosophical Transactions of the Royal Society of London. ISBN 202 525-552.
HP Robertson (1937). Dynamic effects of radiation in the solar system. Monthly Notices of the Royal Astronomical Society. Number 97: pages 423-438.
emc.
Poynting–Robertson effect
Article
Discussion
Lascivious look
Edit
view history
Tools
The Poynting-Robertson effect is a process by which interplanetary dust particles are slowly spiraled toward the Sun by solar radiation. This is because the orbital motion of the dust grains is counteracted by the radiation pressure component tangent to the motion.
Interpretation
The effect can be interpreted in two ways, depending on the reference system from which it is described.
From the perspective of the dust grain, the Sun's radiation appears to come from a slightly tilted angle toward the direction of motion (see light aberration); therefore, the absorption of this incident radiation by the grain (in other words, the transfer of momentum from it to it) results in a net force that opposes its orbital motion. This action is slow, since the angle of aberration is very small (solar radiation moves at the speed of light and the particle moves at a much lower speed).
From the perspective of the Sun (reference system at rest), the dust grain absorbs all the sunlight it receives from the radial direction, perpendicular to its movement and, therefore, its angular momentum does not change; however, the absorbing photons acquire mass (mass-energy equivalence), so to conserve angular momentum, their distance from the Sun must decrease.
Considering the re-emission of the energy absorbed by the grain, note that in the first case (seen from the grain) said re-emission is isotropic (same in all directions), and does not affect the movement. But seen from the Sun, the re-emission is anisotropic and the photons "carry" the angular momentum of the particle, a loss that must be compensated by approaching the Sun.
The action described is very slow, although its effect is cumulative over time: if a particle of a few micrometers (μm) is located at a distance from the Sun equivalent to Earth's orbit (one astronomical unit), it will need about seven thousand years to complete. the spiral towards the Sun. In very small particles (on the order of a fraction of μm or less) the radiation pressure of the Sun predominates and they have, therefore, outward motions. The Poynting-Robertson effect is also more intense near the Sun and tends to reduce the eccentricity of elliptical orbits.
References
JH Poynting (1903). Radiation in the Solar System: its effect on temperature and its pressure on small bodies. Philosophical Transactions of the Royal Society of London. ISBN 202 525-552.
HP Robertson (1937). Dynamic effects of radiation in the solar system. Monthly Notices of the Royal Astronomical Society. Number 97: pages 423-438.