How many moons does Pluto have?
Pluto has five known moons. In order of distance from Pluto, they are Charon, Styx, Nix, Kerberos, and Hydra.
Questions about Moons of Pluto
Short answers, pulled from the story.
Who discovered Charon, Pluto's largest moon?
Charon was discovered by James Christy on the 22nd of June 1978, nearly half a century after Pluto itself was found. Its discovery forced a major revision in estimates of Pluto's size, since previous calculations had incorrectly attributed the entire mass and reflected light of the Pluto-Charon system to Pluto alone.
Why are Pluto and Charon sometimes called a binary dwarf planet?
Charon is massive enough relative to Pluto that the gravitational center of their system lies in open space roughly 960 kilometers above Pluto's surface, not inside either body. Both worlds are also mutually tidally locked, each permanently facing the other. A formal proposal to reclassify them as a double planet was considered at the International Astronomical Union's General Assembly in August 2006 but was ultimately abandoned.
When was the New Horizons spacecraft's Pluto flyby?
New Horizons visited the Pluto system in July 2015. It returned images of Nix at resolutions as fine as 330 meters per pixel and confirmed that no moons larger than 4.5 kilometers in diameter exist within 180,000 kilometers of Pluto.
How were Pluto's moons formed?
Pluto's satellite system is thought to have formed from a massive collision, similar to the impact thought to have created Earth's Moon. The nearly circular orbits and high angular momenta of the moons support a collision origin rather than capture from the Kuiper Belt. The moons' grey color, distinct from Pluto's reddish surface, is attributed to loss of volatile materials during or after the impact, leaving surfaces dominated by water ice.
Do Pluto's moons rotate chaotically?
New Horizons confirmed that Nix, Hydra, Styx, and Kerberos had not tidally spun down and were found at high obliquity. Mark R. Showalter speculated that Nix can flip its entire pole, making its rotation appear almost random. Only Saturn's moon Hyperion is otherwise known to tumble in a similar way.