New but tiny moon found circling distant Pluto

Distant and tiny Pluto has been hiding something from Earth: another moon.

Nasa announced Wednesday that the Hubble Space Telescope has found a fourth moon circling Pluto, which had been demoted from full planet to dwarf planet. Astronomers had been looking to see if Pluto had a ring, but instead they found another object circling the dwarf planet that is 3 billion miles (4.8 billion kilometers) from Earth.

But it is a mini-moon. It is only eight to 21 miles (33 kilometers) wide. Pluto's biggest moon, Charon, is 80 times bigger. The other two moons are Nix and Hydra.

Until astronomers decide a name, this moon is called P4.