The two moons, called P1 and P2 for now, were discovered in May 2005 using the Hubble Space Telescope. Scientists now think the two moons are roughly 37 and 31 miles (60 and 50 km) in diameter. Charon has an estimated diameter of about 750 miles (1,200 km).More details over here
The moons’ tiny sizes raise the possibility that even more satellites might be discovered around Pluto in the future.
Planet Pluto may have rings
Posted on Wednesday, February 22 2006 @ 22:01 CET by Thomas De Maesschalck
Scientists say it is possible that Pluto is encircled by rings fashioned from debris ejected from the surface of its tiny moons.