Pluto Fact Sheet

PLUTO

Pluto/Earth Comparison

Bulk parameters

                                  Pluto          Earth      Ratio (Pluto/Earth)
Mass (10²⁴ kg)                    0.0131         5.9726         0.0022
Volume (10¹⁰ km³)                 0.715        108.321          0.0066
Equatorial radius (km)	           1195           6378.1        0.187
Polar radius (km)                  1195           6356.8        0.188
Volumetric mean radius (km)        1195           6371.0        0.188         
Ellipticity (Flattening)          0.0000         0.00335        0.0
Mean density (kg/m³)               1830           5514          0.332
Surface gravity (m/s²)            0.58           9.80           0.059
Surface acceleration (m/s²)       0.58           9.78           0.059
Escape velocity (km/s)            1.2           11.19           0.107
GM (x 10⁶ km³/s²)                 0.00087        0.3986         0.0022  
Bond albedo                    0.4 - 0.6         0.306        1.3 - 2.0
Visual geometric albedo        0.5 - 0.7         0.367        1.4 - 1.9
Visual magnitude V(1,0)          -1.0           -3.86             -
Solar irradiance (W/m²)           0.89           1367.6         0.0007
Black-body temperature (K)       37.5          254.3            0.147
Number of natural satellites      5              1
Planetary ring system            No             No

Orbital parameters

                                  Pluto           Earth      Ratio (Pluto/Earth)
Semimajor axis (10⁶ km)         5906.38          149.60          39.482
Sidereal orbit period (days)     90,465          365.256        247.68
Tropical orbit period (days)     90,588          365.242        248.02
Perihelion (10⁶ km)             4436.82          147.09          30.164       
Aphelion (10⁶ km)               7375.93          152.10          48.494
Synodic period (days)            366.73             -              -
Mean orbital velocity (km/s)       4.67           29.78           0.157 
Max. orbital velocity (km/s)       6.10           30.29           0.201     
Min. orbital velocity (km/s)       3.71           29.29           0.127    
Orbit inclination (deg)           17.16            0.000           -
Orbit eccentricity                 0.2488          0.0167        14.899
Sidereal rotation period (hrs)  -153.2928         23.9345         6.405
Length of day (hrs)              153.2820         24.0000         6.387
Obliquity to orbit (deg)         122.53           23.44          (2.452)

Pluto Observational Parameters

Discoverer:      Clyde Tombaugh
Discovery Date:  18 February 1930

Distance from Earth
        Minimum (10⁶ km)         4284.7
        Maximum (10⁶ km)         7528.0
Apparent diameter from Earth
        Maximum (seconds of arc)    0.11
        Minimum (seconds of arc)    0.06
Mean values at opposition from Earth
        Distance from Earth (10⁶ km)       5750.54    
        Apparent diameter (seconds of arc)    0.08
        Apparent visual magnitude            15.1      
Maximum apparent visual magnitude            13.65

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 (6:22 a.m. EST), Pluto passed Neptune as the 
furthest planet from the Sun once again and will remain so until 5 April 2231.

North Pole of Rotation

Right Ascension: 313.02
Declination    :   9.09
Reference Date : 12:00 UT 1 Jan 2000 (JD 2451545.0)

Pluto Atmosphere

Surface Pressure: ~3 microbar
Average temperature: ~50 K (-223 C)
Scale height: ~60 km
Mean molecular weight: ~16-25 g/mole
Atmospheric composition:  Methane (CH₄), Nitrogen (N₂)

Charon (P1)

Mean distance from Pluto (km)     19,600        
Sidereal orbit period (days)        6.3872        
Sidereal rotation period (days)     6.3872        
Orbital inclination to Pluto (deg)  0.0       
Orbital eccentricity                0.0
Equatorial radius (km)              593          
Mass (10²¹ kg)                      1.62        
Mean density (kg/m³)               1850
Surface gravity (m/s²)              0.31
Escape velocity (km/s)              0.60  
Geometric albedo                    0.38
Apparent visual magnitude          16.8

Other Moons of Pluto

                Semi-Major    Orbital     Mean Diameter
                Axis (km)  Period (days)      (km)
Nix (P2)          48,700       24.9         46 - 137 
Hydra (P3)        64,750       38.2         61 - 167
Kerberos (P4)     59,000       32.1         13 - 34
Styx (P5)         42,000       20.2         10 - 25