Pluto Fact Sheet

Pluto/Earth Comparison

Bulk parameters

                                  Pluto          Earth      Ratio (Pluto/Earth)
Mass (1024 kg)                    0.0125         5.9736         0.0021
Volume (1010 km3)                 0.616        108.321          0.0057
Volumetric mean radius (km)        1137           6371          0.1785
Mean density (kg/m3)               2050           5520          0.3714
Surface gravity (m/s2)            0.66           9.78           0.0675
Escape velocity (km/s)            1.1           11.19           0.0983
GM (x 106 km3/s2)                 0.00083        0.3986         0.0021
Bond albedo                       0.145          0.385          0.377
Visual geometric albedo           0.3            0.367          0.817
Solar irradiance (W/m2)           0.9            1380           0.0007
Black-body temperature (K)       42.7          247.3            0.1653

Orbital parameters

                                  Pluto           Earth      Ratio (Pluto/Earth)
Semimajor axis (106 km)         5906.4           149.6           39.48
Sidereal orbit period (days)     90,465          365.256        247.68
Tropical orbit period (days)     90,588          365.242        248.02
Perihelion (106 km)             4445.8           147.1           30.22
Aphelion (106 km)               7381.2           152.1           48.53
Synodic period (days)            366.73             -              -
Mean orbital velocity (km/s)       4.75           29.79           0.1594
Orbit inclination (deg)           17.14            0.00            -
Orbit eccentricity                 0.2488          0.0167        14.898
Sidereal rotation period (hrs)   153.2928         23.9345         6.4047
Obliquity to orbit (deg)         122.46           23.45          (2.4563)

Pluto Observational Parameters

Discoverer:      Clyde Tombaugh
Discovery Date:  18 February 1930

Apparent diameter from Earth
        Maximum (seconds of arc)    0.11
        Minimum (seconds of arc)    0.06
Distance from Earth
        Minimum (106 km)         4293.7
        Maximum (106 km)         7533.3
Apparent magnitude at opposition   15.1      

Pluto Mean Orbital Elements (J2000)

Semimajor axis (AU)                 39.48168677
Orbital eccentricity                 0.24880766
Orbital inclination (deg)           17.14175
Longitude of ascending node (deg)  110.30347
Longitude of perihelion (deg)      224.06676
Mean longitude (deg)               238.92881

On 11 February 1999 at 11:22 UT, Pluto passes Neptune as the
furthest planet from the Sun once again for the next 228 years.

Pluto Atmosphere

Surface Pressure: ~3 microbar
Average temperature: ~50 K
Scale height: ~60 km
Mean molecular weight: ~16-25 g/mole
Atmospheric composition:  Methane (CH4), Nitrogen (N2)

Charon

Mean distance from Pluto (km)    19,405
Sidereal orbit period (days)       6.387
Orbital inclination (deg)         96.56
Orbital eccentricity               0.0
Equatorial radius (km)             586
Mass (1021 kg)                     1.7
Mean density (kg/m3)              1800
Surface gravity (m/s2)             0.21
Escape velocity (km/s)             0.58
Albedo                             0.375

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