This is apartial list of Solar System objects by size, arranged in descending order of mean volumetricradius, and subdivided into several size classes. These lists can also be sorted according to an object'smassand, for the largest objects,volume,densityandsurface gravity, insofar as these values are available. This list contains theSun, theplanets,dwarf planets, many of the largersmall Solar System bodies(which includestheasteroids), all namednatural satellites, and a number of smaller objects of historical or scientific interest, such ascometsandnear-Earth objects.The ordering may be different depending on whether one chooses radius ormass, because some objects are denser than others. For instance,Uranusis larger thanNeptunebut less massive, and larger thanMercury, they have less than half Mercury's mass. This means some objectsin the lower tables, despite their smaller radii, may be more massive than objects inthe upper tables because they have a higher density.Manytrans-Neptunian objects(TNOs) have been discovered, and their approximate locations in this list are shown, even though there can be a large uncertainty in their measurement.Solar Systemobjects more massive than 1021kilograms(oneyottagram [Yg]) are known or expected to be approximately spherical. Astronomical bodies relax into rounded shapes (ellipsoids), achievinghydrostatic equilibrium, when the gravity of their mass is sufficient to overcome the structural strength of their material. Objects made of ice become round more easily than those made of rock, and many icy objects are spheroidal at far lower sizes. The cutoff boundary for roundness is somewhere between 100 km and 200 kmin radius.[1]The larger objects in the mass range between 1018kgto 1021 kg (1 to 1000zettagrams [Zg]), such asTethys,Ceres, andMimas, have relaxed to anoblate-spheroidequilibrium due to their gravity, whereas the less massiverubble piles(e.g.AmaltheaandJanus) are roughly rounded,but not spherical, dubbed "irregular".
