Before Pluto was only known to have 1 satellite, But now Scientists add Two more, that are much further Charon (Pluto's 1st known moon). The two new Satellites orbit about 27,000 miles from pluto, which is twice as far as Charon and they are 5 times dimmer than Charon. So its understandable why they werent seen. The moons were found using the Hubble Space Telescope.
Read More about it here [ Space.com ]
View a Short and Two Long Exposures [ View Images ]