From the NASA science news article:
The dwarf planet’s entire moon system is believed to have formed by a collision between Pluto and another planet-sized body early in the history of the solar system. The smashup flung material that coalesced into the family of satellites observed around Pluto.
"This surprising observation is a powerful reminder of Hubble's ability as a general purpose astronomical observatory to make astounding, unintended discoveries," said Jon Morse, astrophysics division director at NASA Headquarters in Washington.The Hubble Space Telescope is such a great instrument. It is capable of such a great amount of observations and has really revolutionized our understanding of the our solar system and galaxy. It has also been utilized as a great science outreach tool. The vast majority of the beautiful pictures of space floating around the internet are courtesy of Hubble. See some of them here: http://www.nasa.gov/hubble.
P4 was first seen in a photo taken with Hubble's Wide Field Camera 3 on June 28. It was confirmed in subsequent Hubble pictures taken on July 3 and July 18. The moon was not seen in earlier Hubble images because the exposure times were shorter. There is a chance it appeared as a very faint smudge in 2006 images, but was overlooked because it was obscured.
The Hubble will eventually fall out of orbit, due mainly to atmospheric drag, sometime between 2019 and 2032. The large range is due to the uncertainty of how active the Sun will be, which effects the amount of drag on the satellite.
The James Webb Space Telescope