This is a list of most likely gravitationally rounded objects (GRO) of the Solar System, which are objects that have a rounded, ellipsoidal shape due to their own gravity (but are not necessarily in hydrostatic equilibrium). Apart from the Sun itself, these objects qualify as planets according to common geophysical definitions of that term. The radii of these objects range over three orders of magnitude, from planetary-mass objects like dwarf planets and some 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.

  SunNASA Solar System exploration Sun factsheet and NASA Sun factsheet NASA Retrieved 2008-11-17 (unless otherwise cited) Symbol (image) Symbol (Unicode) ☉ Discovery year Prehistoric Mean distancefrom the Galactic Center km light years ≈ 2.5 ≈ 26,000 Mean radius km :E 695,508 109.3 Surface area km2 :E 6.0877 11,990 Volume km3 :E 1.4122 1,300,000 Mass kg :E 1.9855 332,978.9Gravitational parameterm3/s21.327×1020 Density g/cm3 1.409 Equatorial gravity m/s2 g 274.027.94 Escape velocity km/s 617.7 Rotation period days 25.38 Orbital period about Galactic Center million years 225–250 Mean orbital speed km/s ≈ 220 Axial tilt to the ecliptic deg. 7.25 Axial tilt to the galactic plane deg. 67.23 Mean surface temperature K 5,778 Mean coronal temperature K 1–2 Photospheric composition H, He, O, C, Fe, S

Planets

In 2006, the International Astronomical Union (IAU) defined 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. In practice, the term "hydrostatic equilibrium" is interpreted more loosely as a requirement for rounding by gravity. Mercury is round but not actually in hydrostatic equilibrium; it is universally regarded as a planet nonetheless.

According to the IAU's explicit count, there are eight planets in the Solar System; four terrestrial planets (Mercury, Venus, Earth, and Mars) and four giant planets, which can be divided further into two gas giants (Jupiter and Saturn) and two ice giants (Uranus and Neptune). When excluding the Sun, the four giant planets account for more than 99% of the mass of the Solar System.

+Key * Terrestrial planet ° Gas giant × Ice giant

  *Mercury *Venus *Earth *Mars °Jupiter °Saturn ×Uranus ×Neptune Symbol or Symbol (Unicode) ☿ ♀ 🜨 ♂ ♃ ♄ ⛢ or ♅ ♆ Discovery year Prehistoric Prehistoric Prehistoric Prehistoric Prehistoric Prehistoric 1781 1846 Mean distancefrom the Sun km AU 57,909,175 0.38709893 108,208,930 0.72333199 149,597,890 1.00000011 227,936,640 1.52366231 778,412,010 5.20336301 1,426,725,400 9.53707032 2,870,972,200 19.19126393 4,498,252,900 30.06896348 Equatorial radius km :E 2,440.53 0.3826 6,051.8 0.9488 6,378.1366 1 3,396.19 0.53247 71,492 11.209 60,268 9.449 25,559 4.007 24,764 3.883 Surface area km2 :E 75,000,000 0.1471 460,000,000 0.9020 510,000,000 1 140,000,000 0.2745 64,000,000,000 125.5 44,000,000,000 86.27 8,100,000,000 15.88 7,700,000,000 15.10 Volume km3 :E 6.083 0.056 9.28 0.857 1.083 1 1.6318 0.151 1.431 1,321.3 8.27 763.62 6.834 63.102 6.254 57.747 Mass kg :E 3.302 0.055 4.8690 0.815 5.972 1 6.4191 0.107 1.8987 318 5.6851 95 8.6849 14.5 1.0244 17Gravitational parameterm3/s22.203×10133.249×10143.986×10144.283×10131.267×10173.793×10165.794×10156.837×1015 Density g/cm3 5.43 5.24 5.52 3.940 1.33 0.70 1.30 1.76 Equatorial gravity m/s2g 3.700.377 8.870.904 9.81.00 3.710.378 24.792.528 10.441.065 8.870.904 11.151.137 Escape velocity km/s 4.25 10.36 11.18 5.02 59.54 35.49 21.29 23.71 Rotation period days 58.646225 243.0187 0.99726968 1.02595675 0.41354 0.44401 0.71833 0.67125 Orbital period days years 87.969 0.2408467 224.701 0.61519726 365.256363 1.0000174 686.971 1.8808476 4,332.59 11.862615 10,759.22 29.447498 30,688.5 84.016846 60,182 164.79132 Mean orbital speed km/s 47.8725 35.0214 29.7859 24.1309 13.0697 9.6724 6.8352 5.4778 Eccentricity 0.20563069 0.00677323 0.01671022 0.09341233 0.04839266 0.05415060 0.04716771 0.00858587 Inclination deg. 7.00 3.39 0 1.85 1.31 2.48 0.76 1.77 Axial tilt deg. 0.0 177.3 23.44 25.19 3.12 26.73 97.86 28.32 Mean surface temperature K 440–100 730 287 227 152 134 76 73 Mean air temperature K 288 165 135 76 73 Atmospheric composition He, Na+K+  CO2, N2, SO2 N2, O2, Ar, CO2 CO2, N2Ar H2, He H2, He H2, HeCH4 H2, HeCH4 Number of known moons 0 0 1 2 115 293 29 16 Rings? No No No No Yes Yes Yes Yes Planetary discriminant 9.1 1.35 1.7 1.8 6.25 1.9 2.9 2.4 Apsidal precession timeperiod asec per yr years 5.75 225,391 2.04 635,294 11.45 113,188 16.28 79,607 6.55 197,862 19.50 66,461 3.34 388,024 0.36 3,600,000 Axial precession timeperiod years 550 29,000 25,600 173,000 473,500 1,800,000 0.72 1,870,000

Dwarf planets

Dwarf planets are bodies orbiting the Sun 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, although only Pluto has actually been confirmed to be in hydrostatic equilibrium (Ceres is close to equilibrium, though some anomalies remain unexplained). Ceres orbits in the asteroid belt, between Mars and Jupiter. The others all orbit beyond Neptune.

+Key† Asteroid belt‡ Kuiper belt§ Scattered disc× Sednoid

  † ‡ ‡ ‡ (unless otherwise cited) § (unless otherwise cited) Symbol or Symbol (Unicode) ⚳ ♇ or ⯓ 🝻 🝼 ⯰ Minor planet number 1 134340 136108 136472 136199 Discovery year 1801 1930 2004 2005 2005 Mean distancefrom the Sun km AU 413,700,000 2.766 5,906,380,000 39.482 6,484,000,000 43.335 6,850,000,000 45.792 10,210,000,000 67.668 Mean radius km :E 0.0737 1,188.30.186 772 0.12 715 0.11 1,163 0.18 Volume km3 :E 4.21 0.00039 6.99 0.0065 1.98 0.0018 1.7 0.0016 6.59 0.0061 Surface area km2 :E 2,770,000 0.0054 17,700,000 0.035 8,140,000 0.016 6,900,000 0.0135 17,000,000 0.0333 Mass kg :E ≈ 0.0002 0.0022 0.0007 ≈ 3.1 0.0005 1.65 0.0028 Gravitational parameter m3/s2 6.263 × 1010 8.710 × 1011 2.674 × 1011 2.069 × 1011 1.108 × 1012 Density g/cm3 2.03 2.43 Equatorial gravity m/s2g 0.270.028 0.620.063 0.630.064 0.400.041 0.820.084 Escape velocity km/s 0.51 1.21 0.91 0.54 1.37 Rotation period days 0.3781 6.3872 0.1631 0.9511 15.7859 Orbital period years 4.599 247.9 283.8 306.2 559 Mean orbital speed km/s 17.882 4.75 4.48 4.40 3.44 Eccentricity 0.080 0.249 0.195 0.161 0.436 Inclination deg. 10.59 17.14 28.21 28.98 44.04 Axial tilt deg. 4 119.6 ≈ 126 ? ≈ 78 Mean surface temperature K 167 40 <50 30 30 Atmospheric composition H2O N2, CH4, CO? N2, CH4 N2, CH4 Number of known moons 0 5 21 1 Rings? No No Yes ? ? Planetary discriminant 0.33 0.077 0.023 0.02 0.10

Astronomers usually refer to solid bodies such as Ceres as dwarf planets, even if they are not strictly in hydrostatic equilibrium. They generally agree that several other trans-Neptunian objects (TNOs) may be large enough to be dwarf planets, given current uncertainties. However, there has been disagreement on the required size. Early speculations were based on the small moons of the giant planets, which attain roundness around a threshold of 200 km radius. However, these moons are at higher temperatures than TNOs and are icier than TNOs are likely to be. Estimates from an IAU question-and-answer press release from 2006, giving 800 km radius and mass as cut-offs that normally would be enough for hydrostatic equilibrium, while stating that observation would be needed to determine the status of borderline cases. Many TNOs in the 200–500 km radius range are dark and low-density bodies, which suggests that they retain internal porosity from their formation, and hence are not planetary bodies (as planetary bodies have sufficient gravitation to collapse out such porosity).W.M. Grundy, K.S. Noll, M.W. Buie, S.D. Benecchi, D. Ragozzine & H.G. Roe, 'The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ()', Icarus (forthcoming, available online 30 March 2019) DOI: 10.1016/j.icarus.2018.12.037,

In 2023, Emery et al. wrote that near-infrared spectroscopy by the James Webb Space Telescope (JWST) in 2022 suggests that Sedna, Gonggong, and Quaoar underwent internal melting, differentiation, and chemical evolution, like the larger dwarf planets Pluto, Eris, Haumea, and Makemake, but unlike "all smaller KBOs". This is because light hydrocarbons are present on their surfaces (e.g. ethane, acetylene, and ethylene), which implies that methane is continuously being resupplied, and that methane would likely come from internal geochemistry. On the other hand, the surfaces of Sedna, Gonggong, and Quaoar have low abundances of CO and CO2, similar to Pluto, Eris, and Makemake, but in contrast to smaller bodies. This suggests that the threshold for dwarf planethood in the trans-Neptunian region is around 500 km radius.

In 2024, Kiss et al. found that Quaoar has an ellipsoidal shape incompatible with hydrostatic equilibrium for its current spin. They hypothesised that Quaoar originally had a rapid rotation and was in hydrostatic equilibrium, but that its shape became "frozen in" and did not change as it spun down due to tidal forces from its moon Weywot. If so, this would resemble the situation of Saturn's moon Iapetus, which is too oblate for its current spin.Cowen, R. (2007). Idiosyncratic Iapetus, Science News vol. 172, pp. 104–106. references Iapetus is generally still considered a planetary-mass moon nonetheless, though not always.

The table below gives Orcus, Quaoar, Gonggong, and Sedna as additional consensus dwarf planets. Slightly smaller Salacia, which is larger than 400 km radius is not often given as a confident dwarf planet candidate, therefore has not been included.

  ‡Orcus ‡Quaoar §Gonggong ×Sedna Symbol Symbol (Unicode) 🝿 🝾 🝽 ⯲ Minor-planet number 90482 50000 225088 90377 Discovery year 2004 2002 2007 2003 Mean distancefrom the Sun km AU 5,896,946,000 39.419 6,535,930,000 43.69 10,072,433,340 67.33 78,668,000,000 525.86 Mean radius km :E 458.5 0.0720 0.0871 615 0.0982 497.5 0.0780 Surface area km2 :E 2,641,700 0.005179 3,870,800 0.007589 4,932,300 0.009671 3,110,200 0.006098 Volume km3 :E 403,744,500 0.000373 716,089,900 0.000661 1,030,034,600 0.000951 515,784,000 0.000476 Mass kg :E 5.48 0.0001 0.0002 1.750.0003 ? Density g/cm3 ≈ ? Equatorial gravity m/s2g 0.017 0.025 0.029 ? Escape velocity km/s ? Rotation period days 9.54? 0.7367 0.9333 0.4280 Orbital period years 247.49 287.97 552.52 12,059 Mean orbital speed km/s 4.68 4.52 3.63 1.04 Eccentricity 0.226 0.038 0.506 0.855 Inclination deg. 20.59 7.99 30.74 11.93 Axial tilt deg. ? 13.6 or 14.0 ? ? Mean surface temperature K ≈ 42 ≈ 41 ≈ 30 ≈ 12 Number of known moons 1 1 (2?) 1 0 Rings? ? Yes ? ? Planetary discriminant 0.003 0.0015 <0.1 ? Absolute magnitude (H) 2.3 2.71 1.8 1.5