G-pluto.T.gif (1179 bytes) Exploring The Planets

Pluto 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

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1998 National Air and Space Museum