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 ...

Pluto was once considered one of the solar system’s planets but was later downgraded to the status of ‘dwarf’ planet after several more similarly sized objects were discovered throughout our solar ...

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 ...

As elementary schoolers, we learned the order of the planets. Maybe your teacher even had a snappy mnemonic like “My Very Educated Mother Just Served Us Nine Pizzas” or “My Very Educated Mother Just ...

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 ...

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) may have detected the dusty hallmarks of an entire family of Pluto-size objects swarming around an adolescent version of our ...