Hubble Telescope Spies Fifth Moon around Pluto

There's something lurking around distant and icy dwarf planet Pluto: a fifth moon.

A team of scientists using the Hubble Space Telescope said Wednesday they have discovered the tiniest moon yet around Pluto. That brings the number of known moons to five.

The mini-moon is estimated to be 6 to 15 miles across, smaller than the one that scientists spotted last year, which is 8 to 21 miles wide. Pluto's largest moon, Charon, is about 650 miles across.

Until the newly found moon gets a name, it will be known as P5.

A NASA spacecraft named New Horizons is speeding toward Pluto where it will arrive in 2015. When New Horizons launched in 2006, Pluto was a full-fledged planet, but astronomers have since demoted it to dwarf planet.