Pluto Diameter:   2390 km, 0.2 Earth Diameters

Planetary Mass:   1.25x1022 kg, 0.0025 Earth masses

Average Distance from Sun:   5.913 billion km, 39.53 AU (astronomical units)

Length of Day:    about 6.4 Earth Days

Length of Year:    248.53 Earth Years

Day/Night Surface Temperature:    54-59 degrees Kelvin

Number of natural satellites:    1 - Charon

Planetary ring system:    No

Average temperature:    ~50 K (-223 C)

Atmospheric composition:    Methane (CH4), Nitrogen (N2)



AU stands for astronomical unit.

One AU is the average distance from the center of the Earth to the center of the Sun:  149,597,870 km

Information on Pluto

Mass (1024 kg)                    0.0125

Volume (1010 km3)                 0.715

Equatorial radius (km)	       1195

Polar radius (km)                  1195

Ellipticity (Flattening)          0.0000

Mean density (kg/m3)               1750

Surface gravity (m/s2)            0.58

Escape velocity (km/s)            1.1

Number of natural satellites      1 - Charon

Planetary ring system            No

Who discovered Pluto?             Clyde Tombaugh discovered Pluto on February 18, 1930.

Pluto Orbital parameters

Semimajor axis (106 km)         5869.66

Sidereal orbit period (days)     90,465

Perihelion (106 km)             4434.99

Aphelion (106 km)               7304.33

Synodic period (days)            366.73

Orbit inclination (deg)           17.16

Orbit eccentricity                 0.2444

Sidereal rotation period (hrs)  -153.2928

Length of day (hrs)              153.2820

Obliquity to orbit (deg)         122.53



Semimajor axis (106 km)          Mean distance of Pluto the planet from the Sun

                                 from center to center in 10^6 kilometers

Sidereal orbit period (days)     The time it takes the body to make one revolution about

                                 the Sun relative to the fixed stars in days.

Synodic period (days)            The time interval between similar configurations in the

                                 orbit (e.g. opposition) of the body and Earth, in days.

Perihelion (106 km)              The point in a body's orbit closest to the

                                 Sun, in 10^6 kilometers.

Aphelion (106 km)                The point in a body's orbit furthest from

                                 the Sun, in 10^6 kilometers.

Orbit inclination (deg)          The inclination of the orbit to the ecliptic, in degrees.

                                 For Plutos moon, this is with respect to Pluto's equator.

Orbit eccentricity               A measure of the circularity of the orbit, equal to

                                 (aphelion - perihelion distance)/(2 x semi-major axis)

                                 For a circular orbit, eccentricity = 0.

Sidereal rotation period (hrs)   The time for one rotation of the body on its axis

                                 relative to the fixed stars, in hours.  A minus sign

                                 indicates retrograde rotation.

Length of day (hrs)              The average time in hours for the Sun to move from the

                                 noon position in the sky at a point on the equator back

                                 to the same position, on Earth this defines a 24 hour day.

Obliquity to orbit (deg)         The tilt of Plutos moon's equator relative to its

                                 orbital plane, in degrees.

Pluto Observational Parameters

Discoverer:      Clyde Tombaugh

Discovery Date:  18 February 1930



Distance from Earth

        Minimum (106 km)         4293.7

        Maximum (106 km)         7533.3

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





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.

Pluto's Atmosphere

Surface Pressure: ~3 microbar

Average temperature: ~50 K (-223 C)

Atmospheric composition:  Methane (CH4), Nitrogen (N2)

Charon

Mean distance from Pluto (km)     19,600

Sidereal orbit period (days)        6.38725

Sidereal rotation period (days)     6.38725

Orbital inclination to Pluto (deg)  0.0

Orbital eccentricity                0.0



Equatorial radius (km)              593

Mass (1021 kg)                      1.9

Mean density (kg/m3)               2000

Surface gravity (m/s2)              0.21

Escape velocity (km/s)              0.58

Albedo                              0.5

Apparent visual magnitude          16.8

Information about Pluto supplied by the NASA Goddard Space Flight Center.

Alternative constants for Pluto by the U.S. Geological Survey: Includes: Radius, orbital period, rotation period, etc.