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Alan Stern calls these satellite planets, although the term major moon is more common. The smallest natural satellite that is gravitationally rounded is Saturn I Mimas (radius 198.2 ± 0.4 km). This is smaller than the largest natural satellite that is known not to be gravitationally rounded, Neptune VIII Proteus (radius 210 ± 7 km).
This structure is thought to arise, in several different ways, from the gravitational pull of Saturn's many moons. Some gaps are cleared out by the passage of tiny moonlets such as Pan , [ 48 ] many more of which may yet be discovered, and some ringlets seem to be maintained by the gravitational effects of small shepherd satellites (similar to ...
The examination of Saturn's gravitational moment, in combination with physical models of the interior, has allowed constraints to be placed on the mass of Saturn's core. In 2004, scientists estimated that the core must be 9–22 times the mass of Earth, [ 44 ] [ 45 ] which corresponds to a diameter of about 25,000 km (16,000 mi). [ 46 ]
Figure 4: Saturn's rings are inside the orbits of its principal moons. Tidal forces oppose gravitational coalescence of the material in the rings to form moons. [12] In the case of an infinitesimally small elastic sphere, the effect of a tidal force is to distort the shape of the body without any change in volume.
Mimas, also designated Saturn I, is the seventh-largest natural satellite of Saturn. With a mean diameter of 396.4 kilometres or 246.3 miles, Mimas is the smallest astronomical body known to be roughly rounded in shape due to its own gravity.
G is the universal gravitational constant (G ≈ 6.67 × 10 −11 m 3 ⋅kg −1 ⋅s −2 [4]) g = GM/d 2 is the local gravitational acceleration (or the surface gravity, when d = r). The value GM is called the standard gravitational parameter, or μ, and is often known more accurately than either G or M separately.
Several prominent examples of secular resonance involve Saturn. There is a near-resonance between the precession of Saturn's rotational axis and that of Neptune's orbital axis (both of which have periods of about 1.87 million years), which has been identified as the likely source of Saturn's large axial tilt (26.7°).
In 2019, twenty new irregular satellites of Saturn were reported, resulting in Saturn overtaking Jupiter as the planet with the most known moons for the first time since 2000. [ 13 ] [ 3 ] In 2019, researchers Edward Ashton, Brett Gladman, and Matthew Beaudoin conducted a survey of Saturn's Hill sphere using the 3.6-meter Canada–France ...