Pluto has long been one of the most debated celestial bodies in our solar system. Once classified as the ninth planet, it was redefined in 2006 as a dwarf planet, a decision that still sparks ...

Since Pluto remains in the sun’s orbit, it should be considered a planet due to the fact that it is still a part of the solar system. And since Pluto is still hanging on at the end of the system, it ...

Washington: NASA's New Horizons probe has settled one of the most basic questions about Pluto - its size. Mission scientists have found Pluto to be 2,370 kms in diameter, somewhat larger than many ...

Editor’s note: A version of this story originally appeared in Astronomy’s 2007 special issue 50 Greatest Mysteries of the Universe. For a more recent discussion of Pluto’s planethood, see “An ...

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