Gravitational scattering

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Gravitational scattering refers to the process by which two or more celestial objects interact through their gravitational fields, causing their trajectories to alter. [1] This phenomenon is fundamental in astrophysics and the study of dynamic systems. [1] When objects like stars, planets, or black holes pass close enough to influence each other’s motions, their paths can shift dramatically. [2] These interactions typically result in either bound systems, like binary star systems, or unbound systems, where the objects continue moving apart after the interaction. [3] An example of a body ejected from a planetary system by this process would be Kuiper belt bodies pushed from the Solar System by Jupiter. [4]

Contents

Observing gravitational scattering

Gravitational scattering events are usually studied using simulations and mathematical models of the gravitational field interactions between bodies. [1] [4] One significant feature of gravitational scattering is the effect of energy exchange. [5] For instance, a high-velocity object may transfer some of its kinetic energy to a slower-moving object, resulting in a slingshot effect. [6] This principle is utilized in space exploration for gravitational assists, where spacecraft gain momentum by passing close to a planet. [6]

Observing gravitational scattering has provided insight into many astrophysical phenomena. [1] In dense regions like star clusters or galactic cores, gravitational scattering plays a role in star formation and the distribution of stellar populations. [7] For instance, hypervelocity stars, which are ejected from their galaxies, are often a result of gravitational scattering involving massive objects like black holes. [3] In more extreme cases, close interactions between compact objects, such as black holes, can lead to the emission of gravitational waves, detectable by instruments like the Laser Interferometer Gravitational-Wave Observatory (LIGO). [8] [9]

Gravitational scattering is analyzed through both Newtonian mechanics and general relativity, with the latter being necessary for systems involving high mass or velocity. [10]

Gravitational scattering impacts

Gravitational scattering can cause orbits to change or even cause celestial bodies to depart their native planetary systems. [3] A possible mechanism that may move planets over large orbital radii is gravitational scattering by larger planets or, in a protoplanetary disk, gravitational scattering by over-densities in the fluid of the disk. [11] In the case of the Solar System, Uranus and Neptune may have been gravitationally scattered onto larger orbits by close encounters with Jupiter and/or Saturn. [8] [4] Systems of exoplanets can undergo similar dynamical instabilities following the dissipation of the gas disk that alter their orbits and in some cases result in planets being ejected or colliding with the star. [8] [4]

Planets scattered gravitationally can end on highly eccentric orbits with perihelia close to the star, enabling their orbits to be altered by the gravitational tides they raise on the star. [12] The eccentricities and inclinations of these planets are also excited during these encounters, providing one possible explanation for the observed eccentricity distribution of the closely orbiting exoplanets. [12] The resulting systems are often near the limits of stability. [13] As in the Nice model, systems of exoplanets with an outer disk of planetesimals can also undergo dynamical instabilities following resonance crossings during planetesimal-driven migration. [4] [14] The eccentricities and inclinations of the planets on distant orbits can be damped by dynamical friction with the planetesimals with the final values depending on the relative masses of the disk and the planets that had gravitational encounters. [14]

See also

Related Research Articles

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<span class="mw-page-title-main">Pebble accretion</span>

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In planetary science a streaming instability is a hypothetical mechanism for the formation of planetesimals in which the drag felt by solid particles orbiting in a gas disk leads to their spontaneous concentration into clumps which can gravitationally collapse. Small initial clumps increase the orbital velocity of the gas, slowing radial drift locally, leading to their growth as they are joined by faster drifting isolated particles. Massive filaments form that reach densities sufficient for the gravitational collapse into planetesimals the size of large asteroids, bypassing a number of barriers to the traditional formation mechanisms. The formation of streaming instabilities requires solids that are moderately coupled to the gas and a local solid to gas ratio of one or greater. The growth of solids large enough to become moderately coupled to the gas is more likely outside the ice line and in regions with limited turbulence. An initial concentration of solids with respect to the gas is necessary to suppress turbulence sufficiently to allow the solid to gas ratio to reach greater than one at the mid-plane. A wide variety of mechanisms to selectively remove gas or to concentrate solids have been proposed. In the inner Solar System the formation of streaming instabilities requires a greater initial concentration of solids or the growth of solid beyond the size of chondrules.

References

PD-icon.svg This article incorporates public domain material from websites or documents of the United States Government .

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