Shape
Proteus is the largest irregularly shaped natural satellite. All other known natural satellites the size of Miranda and above have lapsed into a rounded ellipsoid under hydrostatic equilibrium. The planets are not truly spherical but oblate spheroids, squatter at the pole than at the equator, but with a constant equatorial diameter. The larger natural satellites, however, since they are all tidally locked, are scalene, squat at the poles but with the equatorial axis directed at their planet longer than the axis along their direction of motion. The most distorted natural satellite is Mimas, where the major axis is 9% greater than its polar axis and 5% greater than its other equatorial axis, giving it a notable egg shape. The effect is smaller with the largest natural satellites, where self gravity is greater relative to tidal distortion, especially when they orbit a less massive planet or at a greater distance, as the Moon does.
| Name | Satellite of | Difference in axes | |
|---|---|---|---|
| (km) | (% of mean diameter) | ||
| Mimas | Saturn | 33.4 (20.4, 13.0) | 8.4% (5.1%, 3.3%) |
| Enceladus | Saturn | 16.6 | 3.3% |
| Miranda | Uranus | 14.2 | 3.0% |
| Tethys | Saturn | 25.8 | 2.4% |
| Io | Jupiter | 29.4 | 0.8% |
| The Moon | Earth | 4.3 | 0.1% |
Read more about this topic: Natural Satellite
Famous quotes containing the word shape:
“The work of the world is common as mud.
Botched, it smears the hands, crumbles to dust.
But the thing worth doing well done
has a shape that satisfies, clean and evident.
...
The pitcher cries for water to carry
and a person for work that is real.”
—Marge Piercy (b. 1936)
“And yonder in the gymnasts’ garden thrives
The self-sown, self-begotten shape that gives
Athenian intellect its mastery,
Even the grey-leaved olive-tree
Miracle-bred out of the living stone....”
—William Butler Yeats (1865–1939)
“The gay world that flourished in the half-century between 1890 and the beginning of the Second World War, a highly visible, remarkably complex, and continually changing gay male world, took shape in New York City.... It is not supposed to have existed.”
—George Chauncey, U.S. educator, author. Gay New York: Gender, Urban Culture, and the Making of the Gay Male World, 1890-1940, p. 1, Basic Books (1994)