Name: d c whitbeck
Date: 1993 - 1999
What are Plutos dimensions?
Based on images taken with the repaired Hubble Space Telescope, Pluto has a
diameter of 2320 kilometers (about 3730 miles), to an accuracy of about 1%.
It is thus quite a bit smaller than our Moon, which has a diameter of
3476 km, and much smaller than Earth, which has a diameter of 12,756 km.
As you may know, Earth has a slight equatorial "bulge" (it is not a
sphere, but has an equatorial diameter slightly larger than its polar
diameter). Pluto is probably too small, and rotates too slowly, to have
such a bulge so it is probably almost perfectly spherical.
Pluto has a satellite named Charon which has a diameter of 1270 km. It's
pretty astounding that Hubble can "see" such a small, distant object!
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Update: June 2012