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 from Earth.
But it is a mini-moon. It is only eight to 21 miles 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.
The announcement comes on the 42nd anniversary of NASA's Apollo 11 astronauts Neil Armstrong and Buzz Aldrin landing on our moon.