Pluto may have been kicked out of the planet club but it has gained yet another companion.

Scientists announced the discovery of the smallest moon yet, around the icy orb, bringing the count of its known moons to five.

“We’re not finished searching yet,” said Hal Weaver of Johns Hopkins University, who thinks there may be more.

The discovery was made by a team of scientists who used the Hubble Space Telescope to scout out Pluto’s neighbourhood ahead of a Nasa spacecraft that is scheduled to arrive in 2015.

When the New Horizons craft launched in 2006, Pluto was a fully-fledged planet, but it has since been demoted to dwarf planet status by the International Astronomical Union.

The newfound moon – known as P5 until it gets a proper name – appeared as a faint fleck in the Hubble images. Scientists estimated the mini-moon to be nine to 24 kilometres across, smaller than the still nameless one that they spotted last year, which is 13 to 34 kilometres wide.