Search results
Results from the WOW.Com Content Network
It was once expected that any icy body larger than approximately 200 km in radius was likely to be in hydrostatic equilibrium (HE). [7] However, Ceres (r = 470 km) is the smallest body for which detailed measurements are consistent with hydrostatic equilibrium, [ 8 ] whereas Iapetus (r = 735 km) is the largest icy body that has been found to ...
A size comparison of Neptune and Earth. Neptune's mass of 1.0243 × 10 26 kg [8] is intermediate between Earth and the larger gas giants: it is 17 times that of Earth but just 1/19th that of Jupiter. [g] Its gravity at 1 bar is 11.15 m/s 2, 1.14 times the surface gravity of Earth, [71] and surpassed only by Jupiter. [72]
The moons of the trans-Neptunian objects (other than Charon) have not been included, because they appear to follow the normal situation for TNOs rather than the moons of Saturn and Uranus, and become solid at a larger size (900–1000 km diameter, rather than 400 km as for the moons of Saturn and Uranus).
Jupiter and Saturn are principally made of hydrogen and helium, whilst Uranus and Neptune consist of water, ammonia, and methane. The defining differences between a very low-mass brown dwarf and a massive gas giant (~13 M J) are debated. One school of thought is based on planetary formation; the other, on the physics of the interior of planets.
The temperature of Triton's upper atmosphere, at 95 ± 5 K, is higher than that at its surface, due to heat absorbed from solar radiation and Neptune's magnetosphere. [ 48 ] [ 53 ] A haze permeates most of Triton's troposphere, thought to be composed largely of hydrocarbons and nitriles created by the action of sunlight on methane.
The lower average density and temperature of these objects give them lower index values. Only Titan (a moon of Saturn) is known to hold on to a significant atmosphere despite an overall lower size and density. While Io (a moon of Jupiter) has a low average temperature, surface temperature on the moon varies wildly due to geologic activity. [10]
Saturn has an observed magnetic field generated within its metallic core. [3] Metallic hydrogen is present within the core (in lower abundances than Jupiter). [3] Saturn has a rock and or ice core 10–30 times the mass of the Earth, and this core is likely soluble in the gas envelope above, and therefore it is primordial in composition.
At about 400 km in diameter, it is larger than the Saturnian moon Mimas, which is fully ellipsoidal. This difference may be due to a past collisional disruption of Proteus. [24] The surface of Proteus is heavily cratered and shows a number of linear features. Its largest crater, Pharos, is more than 150 km in diameter. [6] [23]