Nix, formal designation (134340) Pluto II, is a natural satellite of Pluto, with a diameter of 49.8 km across its longest dimension. It was discovered along with Pluto's outermost moon Hydra on 15 May 2005 by astronomers using the Hubble Space Telescope, and was named after Nyx, the Greek goddess of the night.
Nix is the third moon of Pluto by distance, orbiting between the moons Styx and Kerberos.
Nix was imaged along with Pluto and its other moons by the New Horizons spacecraft as it flew by the Pluto system in July 2015. These images reveal a large reddish area on Nix that is likely an impact crater.
Nix was independently discovered by Max Mutchler and Andrew Steffl, members of the Pluto Companion Search Team, using the Hubble Space Telescope. The New Horizons team had suspected that Pluto and its moon Charon might be accompanied by other moons, hence they used Hubble to search for faint moons around Pluto in 2005. Since Nix's brightness is about 5,000 times fainter than Pluto, long exposure images were taken in order to find it.
The discovery images were taken on 15 May 2005 and 18 May 2005. The discoveries were announced on 31 October 2005, after confirmation by precovering archival Hubble images of Pluto from 2002. The two newly announced moons of Pluto were subsequently provisionally designated S/2005 P 1 for Hydra and S/2005 P 2 for Nix. The moons were informally referred to as "P1" and "P2", respectively by the discovery team.
The name Nix was approved by the International Astronomical Union (IAU) and was announced on 21 June 2006 along with the naming of Hydra in the IAU Circular 8723.
Nix was named after Nyx, the Greek goddess of darkness and night and mother of Charon, the ferryman of Hades in Greek mythology. The original proposal for the naming of Nix was to use the classical spelling Nyx, but to avoid confusion with the asteroid 3908 Nyx, the spelling was changed to Nix, the Coptic spelling of the name. The adjectival form of the name is Nictian (cf. Russian Никта Nikta).
More information: NASA
Hydra, formal designation (134340) Pluto III, is a natural satellite of Pluto, with a diameter of approximately 51 km across its longest dimension. It is the second-largest moon of Pluto, being slightly larger than Nix. Hydra was discovered along with Nix by astronomers using the Hubble Space Telescope on 15 May 2005, and was named after the Hydra, the nine-headed underworld serpent in Greek mythology. By distance, Hydra is the fifth and outermost moon of Pluto, orbiting beyond Pluto's fourth moon Kerberos.
Hydra has a highly reflective surface caused by the presence of water ice, similar to other Plutonian moons. Hydra's reflectivity is intermediate, in between those of Pluto and Charon. The New Horizons spacecraft imaged Pluto and its moons in July 2015 and returned multiple images of Hydra.
Members of the New Horizons team suspected that Pluto and Charon might be accompanied by other small, distant moons, weakly bound to the Pluto system. They used the Hubble Space Telescope to test this hypothesis. This led to the discovery of Nix and Hydra -both surprisingly close to Pluto/Charon- and that no significant moons existed in Pluto's extended sphere of influence.
The discovery images were taken on 15 May 2005 and 18 May 2005. Hydra and Nix were independently discovered by Max J. Mutchler on 15 June 2005 and by Andrew J. Steffl on 15 August 2005. The discoveries were announced on 31 October 2005, after confirmation by precovering archival Hubble images of Pluto from 2002. The two newly discovered moons were subsequently provisionally designated S/2005 P 1 for Hydra and S/2005 P 2 for Nix. The moons were informally referred to as "P1" and "P2" respectively, by the discovery team.
The name Hydra was approved on 21 June 2006 by the International Astronomical Union (IAU) and was announced along with the naming of Nix in the IAU Circular 8723.
Hydra was named after the Lernaean Hydra, a multi-headed serpent that battled Heracles/Hercules in Greek and Roman mythology. Particularly, the nine heads of Hydra subtly references Pluto's former ninth planetary status. The two newly named moons were intentionally named that the order of their initials N and H honors the New Horizons mission to Pluto, similarly to how the first two letters of Pluto's name honors Percival Lowell.
The names of features on the bodies in the Pluto system are related to mythology and the literature and history of exploration. In particular, the names of features on Hydra must be related to legendary serpents and dragons from literature, mythology, and history.
More information: NASA
as presents sitting under a Christmas tree.
They're wrapped, and from Earth
all we can do is look at the boxes
to see whether they're light or heavy,
to see if something maybe jiggles a bit inside.
We're seeing intriguing things,
but we really don't know what's in there.
Alan Stern
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