List of Solar System objects by size
This is a partial list of Solar System objects by size, arranged in descending order of mean volumetric radius, and subdivided into several size classes. These lists can also be sorted according to an object's mass and, for the largest objects, volume, density and surface gravity, insofar as these values are available. This list contains the Sun, the planets, dwarf planets, many of the larger small Solar System bodies (which includes the asteroids), all named natural satellites, and a number of smaller objects of historical or scientific interest, such as comets and near-Earth objects.
The ordering may be different depending on whether one chooses radius or mass, because some objects are denser than others. For instance, Uranus is larger than Neptune but less massive, and although Ganymede and Titan are larger than Mercury, they have less than half Mercury's mass. This means some objects in the lower tables, despite their smaller radii, may be more massive than objects in the upper tables because they have a higher density.
Many trans-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 System objects more massive than 1021kilograms (one yottagram [Yg]) are known or expected to be approximately spherical. Astronomical bodies relax into rounded shapes (ellipsoids), achieving hydrostatic 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 km in radius.
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