Facts about Pluto’s moons

Facts about Pluto's moons

Pluto has the following 5 moons:

  • Charon
  • Styx
  • Nix
  • Kerberos
  • Hydra

(ordered by distance from Pluto with Charon as the closest and Hydra as the furthest)

Fact: The moon Charon is large compared to Pluto and its other moons
Attribution: Mysid – Wikipedia.org

Fact: The image shows the relative sizes and colors of Pluto and the moons Charon, Nix and Hydra


The table below provides an overview of the characteristics of the moons. The moons are sorted by date of discovery. Below the table you can read more about the individual moons and the origin of their names.

Your name Discovery date Diameter in km Average distance to the sun Turnaround time in days Eccentricity
Charon 22.06.1978 1.207 17.536 6,387230 0,0022
Nix 15.06.2005 46 or 137 48.708 24,856 0,0030
Hydra 15.06.2005 61 or 167 64.749 38,206 0,0051
Kerberos 28.06.2011 13 or 34 59.000 32,1 Unknown
Styx 11.07.2012 10 or 25 42.000 20,2 Unknown



Descriptions of the individual moons


Pluto’s largest moon, Charon, was discovered in 1978 and is a relatively large moon, being almost half the size of Pluto. The distance between Pluto and Charon is only 19,640 km – in comparison, the distance between Earth and its moon is 384,000 (on average).

Charon has an orbital period of 6 days and 9 hours around Pluto (the same time as 1 day on Pluto). This means that Charon is “locked” around Pluto and is therefore always in the same place in the sky as seen from Pluto. Similarly, Pluto will always be in the same place in the sky as seen from Charon. On Charon, however, there will be some places from which Pluto cannot be seen.

Due to the long distance, Pluto and Charon are difficult to see from Earth. In the late 1980s, Pluto and Charon repeatedly passed each other, giving astronomers some improved opportunities to observe the two.


Nix and Hydra

In 2005, while scientists were studying Pluto as part of the New Horizon mission, they discovered 2 new moons around Pluto. The moons were named Nix and Hydra and are 2-3 times further away from Pluto than Charon.


Cerberus and Styx

In 2011 and 2012, scientists discovered two more moons around Pluto. Their original titles were P4 and P5, but they were later renamed Kerberos and Styx respectively. Like Nix and Hydra, Kerberos and Styx were also found using the Hubble Telescope.


Names of the moons

The name Pluto comes from Roman mythology, where Pluto was the god of the underworld. Similarly, Pluto’s moons are named after other mythological figures from the underworld:

  • Charon is the name of the boatman who sails souls across the river Styx into the underworld
  • Styx is the name of the river that separates the world of the living from the dead
  • Nix is the name of Charon’s mother, who is also the goddess of darkness and night
  • Hydra is the name of a nine-headed serpent that guards the underworld
  • Cerberus is the name of a three-headed dog from Greek mythology