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 (hydrostatic equilibrium). Their sizes range 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

Main article: Sun

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

Sun
Astronomical symbol
Mean distance from the Galactic Center	km light years	~2.5×1017 ~26,000
Mean radius	km :E	695,508 109.3
Surface area	km2 :E	6.0877×1012 11,990
Volume	km3 :E	1.4122×1018 1,300,000
Mass	kg :E	1.9855×1030 332,978.9
Gravitational parameter	m3/s2	1.327×1020
Density	g/cm3	1.409
Equatorial gravity	m/s2	274.0
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	1–2×106
Photospheric composition	H, He, O, C, Fe, S

Planets

Main article: Planet

Key
* Terrestrial planet	° Gas giant	‡ Ice giant

The 2006 International Astronomical Union (IAU) 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 (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.

*Mercury	*Venus	*Earth	*Mars	°Jupiter	°Saturn	‡Uranus	‡Neptune
Astronomical symbol
Mean distance from 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	6.083×1010 0.056	9.28×1011 0.857	1.083×1012 1	1.6318×1011 0.151	1.431×1015 1,321.3	8.27×1014 763.62	6.834×1013 63.102	6.254×1013 57.747
Mass	kg :E	3.302×1023 0.055	4.8690×1024 0.815	5.972×1024 1	6.4191×1023 0.107	1.8987×1027 318	5.6851×1026 95	8.6849×1025 14.5	1.0244×1026 17
Gravitational parameter	m3/s2	2.203×1013	3.249×1014	3.986×1014	4.283×1013	1.267×1017	3.793×1016	5.794×1015	6.837×1015
Density	g/cm3	5.43	5.24	5.52	3.940	1.33	0.70	1.30	1.76
Equatorial gravity	m/s2	3.70	8.87	9.8	3.71	24.79	10.44	8.87	11.15
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 1.000702364	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+ P+	CO2, N2, SO2	N2, O2, Ar, CO2	CO2, N2 Ar	H2, He	H2, He	H2, He CH4	H2, He CH4
Number of known moons	0	0	1	2	79	82	27	14
Rings?	No	No	No	No	Yes	Yes	Yes	Yes
Planetary discriminant	9.1×104	1.35×106	1.7×106	1.8×105	6.25×105	1.9×105	2.9×104	2.4×104

Dwarf planets

Main article: Dwarf planet

Key
† asteroid belt	‡ trans-Neptunian

Dwarf planets 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 using Kepler's third law, 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.

†Ceres	‡Pluto	‡Haumea	‡Makemake	‡Eris
Astronomical symbol
Minor planet number	1	134340	136108	136472	136199
Mean distance from 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	473 0.0742	1,188.3 0.186	816 (2100 × 1680 × 1074) 0.13	715 0.11	1,163 0.18
Volume	km3 :E	4.21×108 0.00039	6.99×109 0.0065	1.98×109 0.0018	1.7×109 0.0016	6.59×109 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	9.39×1020 0.00016	1.30×1022 0.0022	4.01 ± 0.04×1021 0.0007	< 4.4 ×1021 < 0.0007	1.65×1022 0.0028
Gravitational parameter	m3/s2	6.263 × 1010	8.710 × 1011	2.674 × 1011	< 2.937 × 1011	1.108 × 1012
Density	g/cm3	2.16	1.87	2.02	2.10	2.43
Equatorial gravity	m/s2	0.27	0.62	0.63	< 0.57	0.82
Escape velocity	km/s	0.51	1.21	0.91	< 0.91	1.37
Rotation period	days	0.3781	6.3872	0.1631	0.9511	14.560
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	2	1	1
Planetary discriminant	0.33	0.077	0.023	0.02	0.10

Of the remaining trans-Neptunian objects, the most likely dwarf planets include:

Orcus	Salacia	Quaoar	Gonggong	Sedna
Minor-planet number	90482	120347	50000	225088	90377
Semi-major axis	km AU	5,896,946,000 39.419	6,310,600,000 42.18	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	423 0.0664	560.5 0.0870	615 0.0982	497.5 0.0780
Surface area	km2 :E	2,641,700 0.005179	2,248,500 0.004408	3,948,000 0.007741	4,932,300 0.009671	3,110,200 0.006098
Volume	km3 :E	403,744,500 0.000373	317,036,800 0.000396	737,591,000 0.000681	1,030,034,600 0.000951	515,784,000 0.000476
Mass	kg :E	6.32×1020 0.0001	4.9×1020 0.0001	1.41×1021 0.0003	1.75×1021 0.0003	?
Density	g/cm3	1.5±0.3	1.50±0.12	1.99±0.46	1.74±0.16	?
Equatorial gravity	m/s2	0.27	0.18	0.24	0.285	?
Escape velocity	km/s	0.50	0.39	0.45	0.604	?
Rotation period	days	?	?	0.3683	0.9333	0.4280
Orbital period	years	247.49	273.98	287.97	552.52	12,059
Mean orbital speed	km/s	4.68	4.57	4.52	3.63	1.04
Eccentricity	0.226	0.106	0.038	0.506	0.855
Inclination	deg.	20.59	23.92	7.99	30.74	11.93
Mean surface temperature	K	~42	~43	~41	~30	~12
Number of known moons	1	1	1	1	0
Planetary discriminant	0.003	<0.1	0.0015	<0.1	?
Absolute magnitude (H)	2.3	4.1	2.71	1.8	1.5

Satellites

Key
🜨 Satellite of Earth	♃ Satellite of Jupiter	♄ Satellite of Saturn	⛢ Satellite of Uranus	♆ Satellite of Neptune	♇ Satellite of Pluto	E Satellite of Eris

Main article: Planetary-mass moon

See also: List of natural satellites of the Solar System

There are at least 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.^{[citation needed]} 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.

🜨Moon	♃Io	♃Europa	♃Ganymede	♃Callisto	♄Mimas	♄Enceladus	♄Tethys	♄Dione	♄Rhea
Astronomical symbol
Mean distance from primary:	km	384,399	421,600	670,900	1,070,400	1,882,700	185,520	237,948	294,619	377,396	527,108
Mean radius	km :E	1,737.1 0.272	1,815 0.285	1,569 0.246	2,634.1 0.413	2,410.3 0.378	198.30 0.031	252.1 0.04	533 0.084	561.7 0.088	764.3 0.12
Surface area	1×106 km2	37.93	41.910	30.9	87.0	73	0.49	0.799	3.57	3.965	7.337
Volume	1×109 km3	22	25.3	15.9	76	59	0.033	0.067	0.63	0.8	1.9
Mass	1×1022 kg	7.3477	8.94	4.80	14.819	10.758	0.00375	0.0108	0.06174	0.1095	0.2306
Density	g/cm3	3.3464	3.528	3.01	1.936	1.83	1.15	1.61	0.98	1.48	1.23
Equatorial gravity	m/s2	1.622	1.796	1.314	1.428	1.235	0.0636	0.111	0.145	0.231	0.264
Escape velocity	km/s	2.38	2.56	2.025	2.741	2.440	0.159	0.239	0.393	0.510	0.635
Rotation period	days	27.321582 (sync)	1.7691378 (sync)	3.551181 (sync)	7.154553 (sync)	16.68902 (sync)	0.942422 (sync)	1.370218 (sync)	1.887802 (sync)	2.736915 (sync)	4.518212 (sync)
Orbital period about primary	days	27.32158	1.769138	3.551181	7.154553	16.68902	0.942422	1.370218	1.887802	2.736915	4.518212
Mean orbital speed	km/s	1.022	17.34	13.740	10.880	8.204	14.32	12.63	11.35	10.03	8.48
Eccentricity	0.0549	0.0041	0.009	0.0013	0.0074	0.0202	0.0047	0.02	0.002	0.001
Inclination to primary's equator	deg.	18.29–28.58	0.04	0.47	1.85	0.2	1.51	0.02	1.51	0.019	0.345
Axial tilt	deg.	6.68	0	0	0–0.33	0	0	0	0	0	0
Mean surface temperature	K	220	130	102	110	134	64	75	64	87	76
Atmospheric composition	Ar, He Na, K, H	SO2	O2	O2	O2, CO2	H2O, N2 CO2, CH4
Rings?	No	No	No	No	No	No	No	No	No	Yes?

♄Titan	♄Iapetus	⛢Miranda	⛢Ariel	⛢Umbriel	⛢Titania	⛢Oberon	♆Triton	♇Charon	EDysnomia [citation needed]
Mean distance from primary:	km	1,221,870	3,560,820	129,390	190,900	266,000	436,300	583,519	354,759	17,536	37,300
Mean radius	km :E	2,576 0.404	735.60 0.115	235.8 0.037	578.9 0.091	584.7 0.092	788.9 0.124	761.4 0.119	1,353.4 0.212	603.5 0.095	350 0.057
Surface area	1×106 km2	83.0	6.7	0.70	4.211	4.296	7.82	7.285	23.018	4.580	1.5
Volume	1×109 km3	71.6	1.67	0.055	0.81	0.84	2.06	1.85	10	0.92	0.18
Mass	1×1022 kg	13.452	0.18053	0.00659	0.135	0.12	0.35	0.3014	2.14	0.152	0.143
Density	g/cm3	1.88	1.08	1.20	1.67	1.40	1.72	1.63	2.061	1.65	2.52
Equatorial gravity	m/s2	1.35	0.22	0.08	0.27	0.23	0.39	0.35	0.78	0.28	0.78
Escape velocity	km/s	2.64	0.57	0.19	0.56	0.52	0.77	0.73	1.46	0.58	0.74
Rotation period	days	15.945 (sync)	79.322 (sync)	1.414 (sync)	2.52 (sync)	4.144 (sync)	8.706 (sync)	13.46 (sync)	5.877 (sync)	6.387 (sync)	15.785 (sync)
Orbital period about primary	days	15.945	79.322	1.4135	2.520	4.144	8.706	13.46	5.877	6.387	15.785
Mean orbital speed	km/s	5.57	3.265	6.657	5.50898	4.66797	3.644	3.152	4.39	0.2	0.172
Eccentricity	0.0288	0.0286	0.0013	0.0012	0.005	0.0011	0.0014	0.00002	0.0022	0.0062
Inclination to primary's equator	deg.	0.33	14.72	4.22	0.31	0.36	0.14	0.10	157	0.001	0.15
Axial tilt	deg.	0	0	0	0	0	0	0	0	0	0
Mean surface temperature	K	93.7	130	59	58	61	60	61	38	53	34
Atmospheric composition	N2, CH4	N2, CH4

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.