| OBJECT |
ORBITAL SEMI-MAJOR AXIS (A.U.) |
ORBIT PERIOD (Earth years) |
MASS (Earth masses) |
RADIUS (Earth radii) |
NUMBER OF KNOWN MOONS |
ROTATION PERIOD* (days) |
AVERAGE DENSITY |
| (kg/m3) |
(g/cm3) |
| Mercury |
0.39 |
0.24 |
0.055 |
0.38 |
0 |
59 |
5400 |
5.4 |
| Venus |
0.72 |
0.62 |
0.82 |
0.95 |
0 |
-243 |
5200 |
5.2 |
| Earth |
1.0 |
1.0 |
1.0 |
1.0 |
1 |
1.0 |
5500 |
5.5 |
| Moon |
— |
— |
0.012 |
0.27 |
— |
27.3 |
3300 |
3.3 |
| Mars |
1.5 |
1.9 |
0.11 |
0.53 |
2 |
1.0 |
3900 |
3.9 |
| Ceres (asteroid) |
2.8 |
4.7 |
0.00015 |
0.073 |
0 |
0.38 |
2700 |
2.7 |
| Jupiter |
5.2 |
11.9 |
318 |
11.2 |
17(a) |
0.41 |
1300 |
1.3 |
| Saturn |
9.5 |
29.4 |
95 |
9.5 |
18 |
0.44 |
700 |
0.7 |
| Uranus |
19.2 |
84 |
15 |
4.0 |
21(b) |
-0.72 |
1300 |
1.3 |
| Neptune |
30.1 |
164 |
17 |
3.9 |
8 |
-0.67 |
1600 |
1.6 |
| Pluto |
39.5 |
248 |
0.002 |
0.2 |
1 |
-6.4 |
2100 |
2.1 |
| Comet Hale-Bopp |
180 |
2400 |
1.0x 10-9 |
0.004 |
— |
0.47 |
100 |
0.1 |
| Sun |
— |
— |
332,000 |
109 |
— |
25.8 |
1400 |
1.4 |
*A negative rotation period indicates retrograde (backward) rotation relative to the sense in which all planets orbit the Sun.
(a) The 17th moon of Jupiter was discovered in 1999.
(b) Discovering moons of Uranus is an active field.
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