P5 is the Pluto’s fifth satellite which was detected in nine sets of images taken by Hubble’s Wide Field Camera 3 during June and July 2012.
The moon is estimated to have an irregular shape and be between 10km and 25km across.
Seen as a speck of light in Hubble images, the moon is believed to be the result of a collision between Pluto and another large icy object billions of years ago.
“The moons form a series of neatly nested orbits, a bit like Russian dolls,” said leader of the team Mark Showalter of the Seti Institute in Mountain View, US.
Pluto’s largest moon, Charon, was discovered in 1978.
The other three moons, spotted by Hubble in 2006 and 2011, were named Nix, Hydra and P4.
Pluto was discovered by the American Clyde Tombaugh in 1930. It was originally classified as the ninth planet in the Solar System, but was recategorized as a dwarf planet and plutoid due to the discovery that it is only one of several large bodies within the Kuiper belt.
The NASA spacecraft, New Horizons, is currently en route to Pluto to take detailed images of the planet’s system.