Pluto
P
luto Facts

  • Pluto is too faint to be seen with the naked eye. When viewed through a telescope, it looks like a star.
  • Stellar occultations have revealed a tenuous atmosphere on Pluto composed primarily of nitrogen and methane gas.
  • Pluto is cold: -233° C (-390 ° F), just 40° C (72 ° F) above absolute zero. At this temperature, all elements would be frozen but neon, hydrogen, and helium.
  • Measurements indicate Pluto is the smallest planet, 2320 kilometers (1440 miles) in diameter. It is smaller than Earth's Moon.


Discoverer:
Clyde Tombaugh - January 23, 1930
Spacecraft Encounter:
none
Average distance from Sun
39.48 AU 5.906 billion km (3.670 billion mi)
Length of year
248.5 years
Rotation period
6.4 days
Average orbital velocity 4.7 km/sec (3 mi/sec)
Inclination of axis 122.46 degrees
Diameter
2340 km (1454 mi)
Number of satellites 1


Comparisons with Earth
Average distance from Sun
39.5 x Earth
Diameter
0.18 x Earth
Mass
0.002 x Earth
Density
0.36 x Earth

Pluto's Unusual Orbit


The orbit of Pluto is unusual in several ways. It is inclined more than 17° from the ecliptic (the plane in which the orbits of the planets lie). The orbit is also more eccentric (far from circular) than any other planetary orbit. At times, Pluto is closer to the Sun than the orbit of Neptune.

Pluto's Orbit


Every 228 years, Pluto's orbit brings it closer to the Sun than Neptune for a period of 20 years. From 1979 to March 1999, Neptune was the farthest planet from the Sun. 





All information and images on this page were obtained from the National Air and Space Museum.


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