Roche limit

American  

[rohsh, rawsh] / roʊʃ, rɔʃ /

noun

Astronomy.

1. the minimum distance below which a moon orbiting a celestial body would be disrupted by tidal forces or below which a moon would not have formed.

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Roche limit British  

/ rɒʃ /

noun

1. astronomy the distance from the centre of a body, such as a planet, at which the tidal forces are stronger than the mutual gravitational attraction between two adjacent orbiting objects

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Roche limit Scientific  

/ rōsh /

1. The shortest distance at which a satellite not held together by any force other than its own gravity can orbit another celestial body without being torn apart by the tidal force between them. The distance depends on the densities of the two bodies and the orbit of the satellite. If the satellite and the object are of similar densities, the Roche limit is about two and a half times the radius of the larger object. Since most natural satellites are rigid bodies, their tensile strength allows them to orbit much closer than their Roche limit; however, rigid bodies too may be broken up by tidal forces. The rings surrounding Saturn and the other gas giants in the outer solar system may be the orbiting debris of moons that approached much closer than the Roche limit and were fragmented by tidal forces. The limit is named after the French mathematician Edouard Roche (1820–83).

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Etymology

Origin of Roche limit

1885–90; named after French astronomer Édouard Roche (1820–83), who first calculated it

Example Sentences

"With this discovery, we have a ring not just outside the Roche limit, but way beyond it."

From Scientific American • Feb. 11, 2023

Previously, it was thought that rings past the Roche limit wouldn't be able to survive this far out from their parent body.

From Scientific American • Feb. 11, 2023

Among the distant smaller worlds, Chariklo’s rings actually lie a bit beyond the Roche limit.

From New York Times • Feb. 8, 2023

Thus, a ring within the Roche limit would tend to remain a ring, while a ring of debris outside the Roche limit would usually coalesce into a moon.

From New York Times • Feb. 8, 2023

“The Roche limit is when you have so much stress that it shreds physical objects and pulls them apart,” McKinnon explained.

From Slate • Feb. 4, 2022