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History. The innermost and largest moon, Charon, was discovered by James Christy on 22 June 1978, nearly half a century after Pluto was discovered. This led to a substantial revision in estimates of Pluto's size, which had previously assumed that the observed mass and reflected light of the system were all attributable to Pluto alone.


When New Horizons arrived at Pluto, it measured the diameter of the world to be 1,473 miles (2,370 kilometers) across, about two-thirds the diameter of Earth's moon.


A new study provides the best estimate to date of the diameter and heft of Pluto's moon Charon and suggests the satellite likely has no atmosphere. Charon is the largest known moon in relation to ...


NASA’s New Horizons mission has answered one of the most basic questions about Pluto—its size. NASA’s New Horizons mission has answered one of the most basic questions about Pluto—its size. ...


The diameter of Pluto is only 2,390 km across. Just for comparison, that’s about 70% the diameter of the Moon. And it’s a fraction of the size of the Earth; about 18% of the Earth’s diameter.


Pluto has 66% of the diameter of the Earth’s moon and 18% of its mass. While it is now confirmed that Pluto is the largest dwarf planet for around 10 years it was thought that this was Eris. Pluto has a eccentric and inclined orbit.


The same surfaces of Charon and Pluto always face each other, a phenomenon called mutual tidal locking. Charon orbits Pluto every 6.4 Earth days. In Depth. Charon is almost half the size of Pluto. The little moon is so big that Pluto and Charon are sometimes referred to as a double dwarf planet system.


Pluto is more than twice the diameter and a dozen times the mass of the dwarf planet Ceres, the largest object in the asteroid belt. It is less massive than the dwarf planet Eris, a trans-Neptunian object discovered in 2005, though Pluto has a larger diameter of 2376.6 km compared to Eris's approximate diameter of 2326 km.


Because the International Astronomical Union has decided that “planets” and “dwarf planets” are objects that orbit the sun - and anything that orbits a planet (or a dwarf planet) is a “moon”. The size of the object isn’t a part of their definition...


Pluto’s Fifth Moon The Hubble Telescope has discovered a fifth moon in orbit around Pluto. This adds to its current satellites Charon, Nix, Hydra and the unnamed... Charon Moon Facts Charon is the largest and innermost moon of Pluto. It was discovered in 1978 by astronomer James Christy and is nearly 1/8 the mass...