Pluto's diameter in 1950 by Gerard Kuiper, using the 200-inch (505-cm) Hale telescope, gave a figure of under 4,000 miles (6,400 km). Pluto's diameter to be close to 4000 km unusually large and close Kuiper belt object Smoluchowski, Roman. The Solar System. New York: Scientific American Books, 1983: 120. "It's size is very difficult to establish, at present is 4000 km." 4000 km Based speckle interferometry specified Pluto's diameter to be close to 4000 km (i.e., 1.15 that of our Moon); leading to a bulk density of only 0.5 g/ cm3 (cf. Bonneau and Foy, 1980). More exact data on the Uranian and Neptunian satellites Planets X and Pluto reasonable and typical estimate of the albedo, a diameter between 4,000 and 6,000 km is indicated,It would thus appear that taking Pluto's diameter to be about 5,500 km cannot be far wrong. More recently, Halliday has placed an upper limit of 6400 km on the diameter of Pluto from a near occultation of a 15th ... a di...