Uranus Fact Sheet

Uranus/Earth Comparison

Bulk parameters

                                    Uranus      Earth   Ratio (Uranus/Earth)
Mass (1024 kg)                      86.83       5.9736        14.536
Volume (1010 km3)                    6,833    108.321         63.08
Radius (1 bar level) (km)
    Equatorial                      25,559      6,378          4.007
    Polar                           24,973      6,356          3.929
Volumetric mean radius (km)         25,362      6,371          3.981
Ellipticity                          0.023      0.0034         6.76
Mean density (kg/m3)                 1,318      5,520          0.239
Gravity (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                          0.90       0.385          2.338
Visual geometric albedo              0.51       0.367          1.390
Visual magnitude V(1,0)             -7.19      -3.86             -
Solar irradiance (W/m2)              3.71       1,380          0.0027
Black-body temperature (K)          35.9      247.3            0.145
Moment of inertia (I/MR2)            0.225      0.3308         0.680
J2 (x 10-6)                       3343.43    1082.63           3.088    

Orbital parameters

                                    Uranus      Earth   Ratio (Uranus/Earth)
Semimajor axis (106 km)            2,871.0       149.6        19.191
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)                2,734.0       147.1        18.59
Aphelion (106 km)                  3,005.2       152.1        19.76
Synodic period (days)                369.66        -             -
Mean orbital velocity (km/s)           6.82       29.79        0.229
Orbit inclination (deg)                0.770       0.00          -
Orbit eccentricity                     0.04718     0.0167      2.825
Sidereal rotation period (hours)      17.24*      23.9345      0.720
Obliquity to orbit (deg)              97.86       23.45        4.173

* Magnetic coordinates (as determined by the Voyager 2 Radio Science experiment)

Uranus Observational Parameters

Discoverer:      William Herschel
Discovery Date:  13 March 1781

Apparent diameter from Earth
        Maximum (seconds of arc)    4.1
        Minimum (seconds of arc)    3.3
Distance from Earth
        Minimum (106 km)         2581.9
        Maximum (106 km)         3157.3
Apparent magnitude at opposition    5.5      

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

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: >>100 bars
Average temperature: ~58 K
Temperature at 1 bar: ~76 K
Density at 1 bar: ~0.42 kg/m3
Wind speeds: 0-200 m/s
Scale height: 27.7 km
Mean molecular weight: 2.64 g/mole
Atmospheric composition (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(?)

NASA Official: J. H. King, joseph.h.king@gsfc.nasa.gov
Last Updated: 27 November 1998, DRW