Uranus/Earth Comparison
Bulk parameters
Uranus Earth Ratio (Uranus/Earth)
Mass (1024 kg) 86.816 5.9726 14.536
Volume (1010 km3) 6,833 108.321 63.08
Radius (1 bar level) (km)
Equatorial 25,559 6,378.1 4.007
Polar 24,973 6,356.8 3.929
Volumetric mean radius (km) 25,362 6,371.0 3.981
Ellipticity (Flattening) 0.02293 0.00335 6.84
Mean density (kg/m3) 1,271 5,514 0.231
Gravity (eq., 1 bar) (m/s2) 8.87 9.80 0.905
Acceleration (eq., 1 bar) (m/s2) 8.69 9.78 0.889
Escape velocity (km/s) 21.3 11.19 1.903
GM (x 106 km3/s2) 5.794 0.3986 14.536
Bond albedo 0.300 0.306 0.980
Visual geometric albedo 0.51 0.367 1.390
Visual magnitude V(1,0) -7.19 -3.86 -
Solar irradiance (W/m2) 3.71 1,367.6 0.0027
Black-body temperature (K) 58.2 254.3 0.229
Moment of inertia (I/MR2) 0.225 0.3308 0.680
J2 (x 10-6) 3343.43 1082.63 3.088
Number of natural satellites 27 1
Planetary ring system Yes No
Orbital parameters
Uranus Earth Ratio (Uranus/Earth)
Semimajor axis (106 km) 2,872.46 149.60 19.201
Sidereal orbit period (days) 30,685.4 365.256 84.011
Tropical orbit period (days) 30,588.740 365.242 83.749
Perihelion (106 km) 2,741.30 147.09 18.637
Aphelion (106 km) 3,003.62 152.10 19.748
Synodic period (days) 369.66 - -
Mean orbital velocity (km/s) 6.80 29.78 0.228
Max. orbital velocity (km/s) 7.11 30.29 0.235
Min. orbital velocity (km/s) 6.49 29.29 0.222
Orbit inclination (deg) 0.772 0.000 -
Orbit eccentricity 0.0457 0.0167 2.737
Sidereal rotation period (hours) -17.24* 23.9345 0.720
Length of day (hrs) 17.24 24.0000 0.718
Obliquity to orbit (deg) 97.77 23.44 4.171
* Magnetic coordinates (as determined by the Voyager 2 Radio Science experiment)
Uranus Observational Parameters
Discoverer: William Herschel
Discovery Date: 13 March 1781
Distance from Earth
Minimum (106 km) 2581.9
Maximum (106 km) 3157.3
Apparent diameter from Earth
Maximum (seconds of arc) 4.1
Minimum (seconds of arc) 3.3
Mean values at opposition from Earth
Distance from Earth (106 km) 2719.99
Apparent diameter (seconds of arc) 3.9
Apparent visual magnitude 5.5
Maximum apparent visual magnitude 5.32
Uranus Mean Orbital Elements (J2000)
Semimajor axis (AU) 19.19126393 Orbital eccentricity 0.04716771 Orbital inclination (deg) 0.76986 Longitude of ascending node (deg) 74.22988 Longitude of perihelion (deg) 170.96424 Mean Longitude (deg) 313.23218
North Pole of Rotation
Right Ascension: 257.43 Declination : -15.10 Reference Date : 12:00 UT 1 Jan 2000 (JD 2451545.0)
Uranian Magnetosphere
Dipole field strength: 0.228 gauss-Ru3 Dipole tilt to rotational axis: 58.6 degrees Dipole offset (planet center to dipole center) distance: 0.3 Ru along the rotation axis
Note: Ru denotes Uranian radii, here defined to be 25,600 km
Uranian Atmosphere
Surface Pressure: >>1000 bars
Temperature at 1 bar: 76 K (-197 C)
Temperature at 0.1 bar: 53 K (-220 C)
Density at 1 bar: 0.42 kg/m3
Wind speeds: 0-250 m/s
Scale height: 27.7 km
Mean molecular weight: 2.64 g/mole
Atmospheric composition (by volume, uncertainty in parentheses)
Major: Molecular hydrogen (H2) - 82.5% (3.3%); Helium (He) - 15.2% (3.3%)
Methane (CH4) - 2.3%
Minor (ppm): Hydrogen Deuteride (HD) - 148
Aerosols: Ammonia ice, water ice, ammonia hydrosulfide, methane ice(?)
AEROSPACE and ASTRONAUTICS 