Kerberos (moon)

Kerberos (formerly known as S/2011 (134340) 1 and informally as P4) is a small moon of the dwarf planet Pluto. The satellite was discovered on 28 June 2011. It is the fourth moon of Pluto to be discovered. The others are Charon, discovered in 1978, Nix and Hydra, which were discovered in 2005, and Styx, discovered in 2012.
Discovery.
The moon was discovered by a Hubble Space Telescope observing team led by Mark Showalter, while they were trying to find out if Pluto had any rings. Kerberos was first seen in a photo taken with Hubble's Wide Field Camera 3, on June 28, 2011. More photos were taken on July 3 and July 18, 2011, to confirm that it exists. The moon was officially verified and announced on July 20, 2011. Kerberos was not seen in earlier Hubble photos because the exposure times were shorter. The moon may have appeared as a very faint smudge in photos taken in 2006, but was ignored because it was not clear. Kerberos is possibly also visible in images taken in 2010.
Structure.
Kerberos has an estimated diameter of 13–34 km (8–21 miles).
Kerberos and Pluto's other moons are thought to have been created by a cosmic collision between the dwarf planet and another celestial body early in the Solar System's history.