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List of gravitationally rounded objects of the Solar System

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In 2006, the International Astronomical Union defined a planet as a body in orbit around the Sun that was large enough to have achieved hydrostatic equilibrium and to have cleared its neighborhood of similar-sized objects.[1] By this definition, there are eight planets in our Solar System, with those objects in orbit around the Sun that had achieved hydrostatic equilibrium but had not cleared their neighborhoods classified as dwarf planets and the remainder termed small Solar System bodies. However, many other objects in the Solar System, including the Sun itself, up to 20 natural satellites and potentially dozens of small Solar System bodies, are also large enough to have achieved hydrostatic equilibrium. All known spherical or spheroidal objects in the Solar System are listed below, with a sample of the largest objects in the Solar System whose shape has yet to be accurately determined. The Sun's orbital characteristics are listed in relation to the Galactic centre. All other objects are listed in order of their distance from the Sun.

Sun

The Sun is a yellow dwarf star. It contains almost 99.9 percent of all the mass in the Solar System.

Sun
Astronomical symbol Mercury
Mean distance
from Galactic center 		km
light years 		~2.5×1017
~26,000
Mean radius km
:E[2] 		1,392,000,000
109
Surface area km²
:E[2] 		6.0877×1018
11,990
Volume km3
:E[2] 		1.4122×1027
1,300,000
Mass kg
:E[2] 		1.9891×1030
332,946
Density g/cm3 1.141
Equatorial gravity m/s2 274.0
Escape velocity km/s 617.7
Rotation period days[3] 25.38
Orbital period about Galactic center years 2.25–2.50×108
Mean orbital speed km/s ~2.20×105
Axial tilt[4] to the ecliptic deg. 7.25
Axial tilt[4] to the galactic plane deg. 67.23
Mean surface temp. K 5,778
Mean coronal temp. K ~5×106
Photospheric composition H, He, O, C, Fe, S

Planets

These objects both are large enough to have achieved hydrostatic equilibrium, and have cleared their neighborhoods of similar objects. The four gas giants combined comprise more than 99 percent of the mass in the Solar System other than the Sun.

Key
¿
terrestrial planet 		†
gas giant
¿ Mercury ¿ Venus ¿ Earth ¿ Mars †Jupiter †Saturn †Uranus †Neptune
File:Uranus Voyager 2.jpg
Astronomical symbol Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune
Mean distance
from Sun 		km
AU 		57,909,175
0.38709893 		108,208,930
0.72333199 		149,597,870
1 		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
Mean radius km
:E[2] 		2,439.64
0.3825 		6,051.59
0.9488 		6,378.15
1 		3,397.00
0.53226 		71,492.68
11.209 		60,267.14
9.449 		25,557.25
4.007 		24,766.36
3.883
Surface area km²
:E[2] 		75,000,000
0.1471 		460,000,000
0.9010 		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[2] 		6.083×1010
0.056 		9.28×1011
0.87 		1.083×1012
1 		1.6318×1011
0.151 		1.431×1015
1,321.3 		8.27×1014
763.59 		6.834×1013
63.086 		6.254×1013
57.74
Mass kg
:E[2] 		3.302×1023
0.055 		4.8690×1024
0.815 		5.9742×1024
1 		6.4191×1023
0.107 		1.8987×1027
318 		5.6851×1026
95 		8.6849×1025
14 		1.0244×1026
17
Density g/cm3 5.43 5.24 5.515 3.940 1.33 0.70 1.30 1.76
Equatorial gravity m/s2 3.70 8.87 9.81 3.71 23.12 8.96 8.69 11.00
Escape velocity km/s 4.25 10.36 11.18 5.02 59.54 35.49 21.29 23.71
Rotation period days[3] 58.646225 -243.0187[5] 0.99726968 1.02595675 0.41354 0.44401 -0.71833[5] 0.67125
Orbital period years[3] 0.2408467 0.61519726 1.0000174 1.8808476 11.862615 29.447498 84.016846 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. 7.00487 3.39471 0.00005 1.85061 1.30530 2.48446 0.76986 1.76917
Axial tilt[4] deg. 0.0 177.3 23.45 25.19 3.12 26.73 97.86 29.58
Mean surface temp. K 440 730 288-293 186-268 152 134 [6] 76 [6] 72 [6]
Mean air temp.[7] K 288 165 135 76 73
Atmospheric composition He  Na+  P+  CO2  N2 N2  O2 CO2  N2  Ar H2  He H2  He H2  He  CH4 H2  He  CH4
Number of known moons 0 0 1 2 63 60 27 13
Rings? No No No No Yes Yes Yes Yes
Planetary discriminant[8] 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

These objects are large enough to have achieved hydrostatic equilibrium, but have not cleared their neighborhoods of similar objects. Ceres is an asteroid between the orbits of Mars and Jupiter. The others all lie beyond Neptune's orbit.

Key
‡
Main belt asteroid 		♠
Trans-Neptunian object
‡ Ceres ♠ Pluto ♠ Haumea ♠ Makemake ♠ Eris
Astronomical symbol Ceres Pluto
Mean distance
from Sun 		km
AU 		413.7 million 
2.766 		5,906 million 
39.482 		6,484,000,000
43.335 		6,850 million 
45.792 		10,210 million 
67.668
Mean radius km
:E[2] 		471
0.0738 		1,148.07
0.180 		980
0.1537 		750+200
−100
0.12 		1,200
0.19
Volume km3
:E[2] 		4.37×108
0.0005 		6.33×109
0.007 		1.3–1.6×109
0.001 		1.8×109
0.002 		7.23×109
0.008
Surface area km²
:E[2] 		2,800,000
0.0055 		17,000,000
0.0333 		7,000,000
0.015 		18,000,000
0.0353
Mass kg
:E[2] 		9.5×1020
0.00016 		1.3×1022
0.0022 		4.2 ± 0.1×1021
0.0007 		4×1021
0.0007 		1.7×1022
0.0028
Density g/cm3 2.08 2.0 2.6–3.3[9] 2.0 2.25
Equatorial gravity m/s2 0.27 0.60 0.44 0.5 ~0.8
Escape velocity km/s 0.51 1.2 0.44 0.8
Rotation period days[3] 0.3781 -6.38718[5] 0.167 >0.33?
Orbital period years[3] 4.599 247.92065 285.4 309.9 557
Mean orbital speed km/s 17.882 4.7490 4.484 4.4 3.436
Eccentricity 0.080 0.24880766 0.18874 0.159 0.44177
Inclination deg. 10.587 17.14175 28.19 28.96 44.187
Axial tilt[4] deg. 4 119.61
Mean surface temp. K 167 40 <50 30 30
Mean air temp.[7] K
Atmospheric composition H2O, O2 N2, CH4 N2, CH4 N2, CH4
Number of known moons No 3 2 No 1
Planetary discriminant[8] 0.33 0.077 0.023 0.02 0.10

Spheric satellites

This table lists the 20 natural satellites in the Solar System large enough to have achieved hydrostatic equilibrium. Proteus, though irregular, is nonetheless larger than Mimas, which is spheroid. Satellites are listed first in order from the Sun, and second in order from their parent body.

Key
€
Satellite of Earth 		₤
Satellite of Jupiter 		$
Satellite of Saturn 		₩
Satellite of Uranus 		₫
Satellite of Neptune
Satellite of Pluto


€ Moon ₤ Io ₤ Europa ₤ Ganymede ₤ Callisto $ Mimas $ Enceladus $ Tethys $ Dione $ Rhea
File:TethysV2.jpg
Astronomical symbol Moon
Mean distance
from primary: 		km 384,399 421,700 670,900 1,070,400 1,882,700 185,520 237,948 294,619 377,396 527,108
Mean radius km
:E[2] 		1,737.1
0.273 		1,821.3
0.286 		1,569
0.245 		2634.1
0.413 		2410.3
0.378 		198.30
0.031 		252.1
0.04 		533
0.083 		561.7
0.088 		764.3
0.12
Surface area km²
:E[2] 		37,930,000
0.074 		41,910,000
0.082 		30,900,000
0.061 		87,000,000
0.143 		73,000,000
0.143 		490,000
0.0001[10] 		799,000
0.0016[10] 		4,940,000
0.001[10] 		3,965,000
0.0078[10] 		7,337,000
0.0144[10]
Volume km3
:E[2] 		2.2×1010
0.02 		2.53×1010
0.02 		1.59×1010
0.07 		7.6×1010
0.15 		5.9×1010
0.05 		3.3×107
0.00003 		6.7×107
0.00006 		6.3×108
0.0006 		7.4×108
0.0007 		1.9 ×109
0.0017
Mass kg
:E[2] 		7.3477×1022
0.0123 		8.9319×1022
0.015 		4.80×1022
0.008 		1.4819×1023
0.025 		1.0758×1023
0.018 		3.75×1019
0.000006 		1.08×1020
0.000018 		1.0244×1020
0.000017 		1.095×1021
0.0003 		2.306×1021
0.0004
Density g/cm3 3.3464 3.528 3.01 1.936 1.83 1.15 1.61 1.15 1.48 1.23
Equatorial gravity m/s2 1.622 1.796 1.314 1.428 1.235 0.0636 0.111 0.064 0.231 0.264
Escape velocity km/s 2.38 2.56 2.025 2.741 2.440 0.159 0.239 0.159 0.510 0.635
Rotation period days[3] 27.321582
(sync)[11] 		1.7691378
(sync) 		3.551181
(sync) 		7.154553
(sync) 		16.68902
(sync) 		0.942422
(sync) 		1.370218
(sync) 		0.942422
(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 1.887 802 2.736915 4.518212
Mean orbital speed km/s 1.022 17.334 13.740 10.880 8.204 14.32[12] 12.63[12] 11.35[12] 10.03[12] 8.48[12]
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 0.05 0.47 1.85 0.2 1.51 0.02 1.51 0.019 0.345
Axial tilt to orbital plane deg. 6.687 0 0.1 0–0.33 0 0 0 0 0 0
Mean surface temp. K 220 130 102 110 134 64 75 64 87 76
Atmospheric composition H  He Na+  K+ Ar 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 ₫ Proteus ₫ Triton Charon
Mean distance
from primary: 		km 1,221,870 3,560,820 129,390 190,900 266,000 436,300 583,519 117,647 354,759 17,536
Mean radius km
:E[2] 		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 		210
0.033 		1353.4
0.212 		603.5
0.095
Surface area km²
:E[2] 		83,000,000
0.163 		6,700,000
0.013 		700,000
0.0014 		4,211,300
0.008 		4,296,000
0.008 		7,820,000
0.015 		7,285,000
0.014 		554,000
0.001[13] 		23,018,000
0.045 		4,580,000
0.009
Volume km3
:E[2] 		7.16×1010
0.066 		1.67×109
0.0015 		5.5×107
0.00005 		8.1×108
0.0008 		8.4×108
0.0008 		2.06×109
0.0019 		1.85×109
0.0017 		3.4×107
0.00003 		1×1010
0.00958 		9.2×108
0.00085
Mass kg
:E[2] 		1.3452×1023
0.023 		1.8053×1021
0.0003 		6.59×1019
0.00001 		1.35×1021
0.00022 		1.2×1021
0.0002 		3.5×1021
0.0006 		3.014×1021
0.00046 		8×1017
0.0000001? 		2.14×1022
0.00358 		1.52×1021
0.00025
Density g/cm3 1.88 1.08 1.20 1.67 1.40 1.72 1.63 0.02? 2.061 1.65
Equatorial gravity m/s2 1.35 0.22 0.08 0.27 0.23 0.39 0.35 0.06 0.78 0.28
Escape velocity km/s 2.64 0.57 0.19 0.56 0.52 0.77 0.73 0.16 1.46 0.58
Rotation period days[3] 15.945
(sync) 		79.322
(sync) 		1.414
(sync) 		2.52
(sync) 		4.144
(sync) 		8.706
(sync) 		13.46
(sync) 		1.122
(sync) 		5.877
(sync) 		6.387
(sync)
Orbital period about primary days 15.945 79.322 1.4135 2.520 4.144 8.706 13.46 1.122 5.877
(retro)[14] 		6.387
Mean orbital speed km/s 5.57[12] 3.265[12] 6.657[12] 5.50898[12] 4.66797[12] 3.644[12] 3.152[12] 7.623[12] 4.39[12] 0.2[12]
Eccentricity 0.0288 0.0286 0.0013 0.0012 0.005[15] 0.0011 0.0014 0.0005 0.00002 0.0022
Inclination to primary's equator deg. 18.29–28.58 0.34854 15.47 4.2 0.26 0.36[15] 0.34 0.52 157 0?
Axial tilt[4] deg. 0 0 0 0? 0 0 0? 0 0
Mean surface temp. K 93.7 130 59 58 61 60 61 51 38 53
Atmospheric composition N2, CH4 N2, CH4

Largest small Solar System bodies

See also: Small Solar System bodies

These trans-Neptunian objects are hypothetically large enough to be given dwarf planet status in future. A further 30 or so TNOs could also eventually be included.[16]

Key
♠
Trans-Neptunian object
♠90482 Orcus ♠28978 Ixion ♠(55637) 2002 UX25 ♠2002 MS4 ♠(145452) 2005 RN43 ♠20000 Varuna ♠(55636) 2002 TX300 ♠50000 Quaoar ♠(55565) 2002 AW197 ♠90377 Sedna
File:Nasa sedna art.jpg
Semi-major axis km
AU 		5,896,946,000
39.419 		5,935,999,000
39.68 		6,212,804,940
41.53 		6,268,156,200
41.9 		6,362,402,940
42.53 		6,451,398,000
43.13 		6,453,572,000
43.14 		6,493,296,000
43.6 		7,073,647,000
47.28 		78,668,000,000
525.86
Mean radius km
:E[2] 		473
0.0742 		411
0.0644 		~325
0.051 		~363
0.057 		~365
0.057 		294
0.0462 		437
0.0685 		625
0.0980 		350
0.0550 		745
0.0117
Surface area km²
:E[2] 		2,812,000
0.0055 		2,122,000
0.00415 		1,327,000
0.0026 		1,655,900
0.0032 		1,674,000
0.0033 		1,091,000
0.00214 		2,399,000
0.00469 		4,906,000
0.0096 		1,359,000
0.0030 		6,971,000
0.0136
Volume km3
:E[2] 		443,506,000
0.0004 		290,689,000
0.0002 		143,793,000
0.0001 		200,358,829
0.0001 		203,689,000
0.0001 		107,217,000
0.0001 		349,420,000
0.0003 		1,022,217,000
0.0009 		179,518,000
0.0001 		1,731,298,000
0.0016
Mass kg
:E[2] 		6.2×1020
0.0001 		6×1020
0.0001 		8×1020
0.00013 		~1.3×1020
0.00001 		? 2.65×1020
0.00004 		5.9×1020
0.0001 		2×1021
0.0003 		5.2×1020
0.00009 		3 ×1021
0005
Density g/cm3 1.5 2.0 2.0 2.0 ? 2.0 1.0 2.6–3.3 2.0 2.0
Equatorial gravity m/s2 0.2 0.23 0.25 0.12–0.33 ? 0.39 0.15–0.20 0.28–0.38 0.22 0.33–0.50
Escape velocity km/s ~0.44 <0.4346? 0.4811 0.22–0.63 ? 0.39 0.28–0.37? 0.276-0.376 0.2216? 0.62-0.95
Rotation period days[3] 0.55 ? 0.6–0.7 ? ? 0.13216 0.33 or 0.66 ? ? 0.42
Orbital period years[3] 247.492 249.95 277.31 271.48 267.60 283.20 283.35 287.97 325.15 12,059.06
Mean orbital speed km/s 4.68 4.66 4.54 4.58 4.63 4.53 4.52 4.52 4.31 1.04
Eccentricity 0.22552 0.242 0.142 0.139 0.023 0.051 0.124 0.0384 0.132 0.855
Inclination deg. 0.22552 19.584 19.482 17.667 19.3 17.2 25.856 7.988 24.410 11.934
Mean surface temp. K ~45 ~44 ~43 ~43 ~43–41 <41 ~43 ~39–40 <33
Number of known moons 1 ? 1 ? ? ? ? 1 ? ?
Planetary discriminant[8] 0.003 0.003 0.003 0.003 0.003 0.0013 0.003 0.01 0.003 ?

Notes

  1. ^ "IAU 2006 General Assembly: Result of the IAU Resolution votes" (Press release). International Astronomical Union (News Release - IAU0603). 2006-08-24. Retrieved 2007-12-31. (orig link)
  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x relative to Earth.
  3. ^ a b c d e f g h i sidereal.
  4. ^ a b c d e The inclination of the body's equator from its orbit.
  5. ^ a b c retrograde orbit.
  6. ^ a b c At pressure of 1 bar
  7. ^ a b At sea level.
  8. ^ a b c Used to distinguish between planet and dwarf planet.
  9. ^ D. L. Rabinowitz, K. M. Barkume, M. E. Brown, H. G. Roe, M. Schwartz, S. W. Tourtellotte, C. A. Trujillo (2006). "Photometric Observations Constraining the Size, Shape, and Albedo of 2003 EL61, a Rapidly Rotating, Pluto-Sized Object in the Kuiper Belt". The Astrophysical Journal. 639 (2): 1238–1251. doi:10.1086/499575. {{cite journal}}: |format= requires |url= (help); External link in |format= (help)CS1 maint: multiple names: authors list (link)
  10. ^ a b c d e Assuming sphericity
  11. ^ This object's rotation is synchronous with its orbital period, meaning that it only ever shows one face to its primary.
  12. ^ a b c d e f g h i j k l m n o Assuming a circular orbit)
  13. ^ Assuming sphericity
  14. ^ retrograde orbit; it orbits opposite to the primary's rotation
  15. ^ a b Umbriel NASA factsheet
  16. ^ Mike Brown. "The Dwarf Planets". CalTech. Retrieved 2008-09-25.

See also

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