Kerberos (moon)

Kerberos is a small natural satellite of Pluto, about 12 km (7.5 mi) in its longest dimension. It was the fourth moon of Pluto to be discovered and its existence was announced on 20 July 2011. It was imaged, along with Pluto and its four other moons, by the New Horizons spacecraft in July 2015. The first image of Kerberos was released to the public on 22 October 2015.
== History ==
=== Discovery ===
Kerberos was discovered by the Pluto Companion Search Team using the Hubble Space Telescope on 28 June 2011, using the Wide Field Camera 3, during an attempt to find any rings that Pluto might possess. Further observations were made on 3 and 18 July 2011 and Kerberos was verified as a new moon on 20 July 2011. It was later 'precovered' (identified in earlier archival Hubble images) in images from 15 February 2006 and 25 June 2010. Kerberos's brightness is only about 10% of that of Nix, and it was only found because the discovery team took 8-minute exposures; earlier observations had used shorter exposures.
The provisional designation of the satellite varied based on the source used. The International Astronomical Union announced it as S/2011 (134340) 1, whereas the New Horizons mission website announced it as S/2011 P 1.
=== Naming ===
Upon discovery, Kerberos received the minor planet designation S/2011 (134340) 1 because it was the first satellite (S) discovered orbiting minor planet (134340) in 2011. It was initially called "P4", meaning the fourth Plutonian moon to be discovered.
The convention for naming Plutonian moons is to use names associated with the god Pluto in classical mythology. To decide on names for P4 and P5, Mark Showalter and the SETI Institute, on behalf of the discovery team, conducted a non-binding Internet poll in 2013, in which the general public was invited to vote for their favourite names. The public could choose from a selection of Greek mythological names related to the god Pluto, or could propose their own names. After the initial announcement, Cerberus, (the dog that guards Pluto's underworld) came first and Styx (the goddess of the river of the underworld) came second. The winning names were submitted to the International Astronomical Union. However, Cerberus was already the name of an asteroid, 1865 Cerberus, but the Greek form of the name, Kerberos, was acceptable to the IAU.
On 2 July 2013, the IAU announced that it formally approved the names Kerberos for P4 and Styx for P5.
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 Kerberos must be related to dogs from literature, mythology and history.
== Physical Properties ==
Kerberos has a double-lobed shape and is approximately 7.4 mi (11.9 km) across in its long dimension and 2.8 mi (4.5 km) in its shortest dimension. Kerberos has an albedo similar to the other three small moons. Until the New Horizons flyby it was thought that Kerberos was larger and darker. Like the other small Plutonian satellites, Kerberos is not tidally locked; its rotational period was about 5.33 days at the time of the New Horizons flyby, although this varies quickly over geological timescales.
== Orbit ==
Observations indicate a circular, equatorial orbit with a radius of approximately 58,000 km (36,000 mi). Kerberos orbits between Nix and Hydra and makes a complete orbit around Pluto roughly every 32.1 days. This period is close to a 1:5 orbital resonance with Charon, with the timing discrepancy being about 0.7%. As with the near resonances between Nix or Hydra and Charon (1:4 and 1:6, respectively), determining how close this relationship is to a true resonance will require more-accurate knowledge of Kerberos's orbit, in particular its rate of precession.
== Origin ==
Like Pluto's other satellites, it is suspected that Kerberos coalesced from the debris of a massive collision between Pluto and another Kuiper belt object, similar to the giant impact thought to have created the Moon.
== Exploration and Use in Space Exploration ==
The New Horizons spacecraft took images of Kerberos during its flyby of the Pluto system on 14 July 2015. Three months later, on 22 October, the first image of the moon was published. It is the last moon to have its picture released.
In the 2130s Kerberos was planned to be used to test a new ship capable of continuous system travel. Whether or not it was actually used in the testing process is unknown.
== In Science Fiction (non-canon) ==
Author Edmond Hamilton referred to three moons of Pluto in his 1940 novel Calling Captain Future, naming them Charon, Styx, and Cerberus.
Kerberos was where the plot of Voltron: Legendary Defender began, though it is incorrectly depicted as spherical. The moon's description was not properly taken into account, yet it remained such a minor detail that the issue was dropped when the show aired.
== In the Timeline ==
=== Space Travel (1969) ===
In Space Travel a ship is tested by travelling to and landing on various planets and moons within the Solar System. Pluto was one such planet used in the testing process so it is probable that some of its moons were used as well.
== Notes ==
* This page was originally taken from Wikipedia. Link: https://en.wikipedia.org/wiki/Kerberos_(moon)