List of gravitationally rounded objects of the Solar System


This is a list of possibly gravitationally rounded objects of the Solar System, which are objects that have a rounded, ellipsoidal shape due to their own gravity. Their sizes range from former dwarf planets and moons to the planets and the Sun. This list does not include small Solar System bodies, but it does include a sample of possible planetary-mass objects whose shapes have yet to be determined. The Sun's orbital characteristics are listed in relation to the Galactic Center, while all other objects are listed in order of their distance from the Sun.

Star

The Sun is a G-type main-sequence star. It contains almost 99.9% of all the mass in the Solar System.

Planets

The 2006 International Astronomical Union defines a planet as a body in orbit around the Sun that was large enough to have achieved hydrostatic equilibrium and to have "cleared the neighbourhood around its orbit". The practical meaning of "cleared the neighborhood" is that a planet is comparatively massive enough for its gravitation to control the orbits of all objects in its vicinity. By the IAU's definition, there are eight planets in the Solar System; four terrestrial planets and four giant planets, which can be divided further into two gas giants and two ice giants. When excluding the Sun, the four giant planets account for more than 99% of the mass of the Solar System.

Dwarf planets

s are bodies that are massive and warm enough to have achieved hydrostatic equilibrium, but have not cleared their neighbourhoods of similar objects. Since 2008, there have been five dwarf planets recognized by the IAU, though of these only Ceres, which orbits in the asteroid belt between the orbits of Mars and Jupiter, has been confirmed. The others all orbit beyond Neptune. Astronomers generally agree that several other trans-Neptunian objects may be large enough to be dwarf planets, given current uncertainties. It seems that dark, low-density objects like Salacia retain internal porosity from their formation, and thus are not planetary bodies. Both Quaoar and Orcus have moons that have allowed their mass and density to be determined, and they are either bright enough to suggest resurfacing and thus planetary geology at least at some point in their past, or are dense enough that they are clearly solid bodies and thus at least potentially dwarf planets.
Of the remaining trans-Neptunian objects, the most likely dwarf planets include:

Satellites

There are 19 natural satellites in the Solar System that are known to be massive enough to be close to hydrostatic equilibrium. Alan Stern calls these satellite planets, although the term major moon is more common.
Several of these were once in equilibrium but are no longer: these include Earth's moon and all of the moons listed for Saturn apart from Titan and Rhea. The status of the moons of Uranus, Pluto and Eris are uncertain. Other moons that were once in equilibrium but are no longer very round, such as Saturn's Phoebe, are not included.
Satellites are listed first in order from the Sun, and second in order from their parent body.

Unless otherwise cited:

Manual calculations (unless otherwise cited)

Individual calculations

Other notes