Styx，Nyx，Hydra和Kerberos是微小的世界，其轨道距离是Charon与冥王星的距离的两到四倍。它们形状奇特，这使得它们形成了冥王星过去碰撞的一部分。 Styx是在2012年被发现的，因为天文学家正在使用哈勃太空望远镜在系统中搜索冥王星周围的卫星和环。它似乎有一个细长的形状，大约3乘4.3英里。 Nyx的轨道超出了Styx，并于2006年与远处的Hydra一起被发现。这是大约33乘25乘22英里，使它有点奇怪的形状，并制作一个冥王星轨道需要将近25天。它可能有一些与Charon在其表面上蔓延相同的tholins，但New Horizo ns并没有足够接近以获得许多细节。 Hydra是冥王星五个卫星中距离最远的地方，而New Horizo ns在航天器经过时能够获得相当好的形象。在其粗糙的表面上似乎有一些陨石坑。 Hydra的测量值大约为34乘25英里，大约需要39天才能在冥王星周围进行一次轨道运动。最神秘的月亮是Kerberos，在New Horizo ns任务图像中看起来像块状和畸形。它似乎是一个双叶的世界，大约11 12 x 3英里。在冥王星周围旅行需要5天多的时间。关于Kerberos的知之甚少，这是由天文学家在2011年使用哈勃太空望远镜发现的。
Styx, Nyx, Hydra and Kerberos are tiny worlds that orbit between two and four times the distance that Charon does from Pluto. They’re oddly shaped, which lends credence to the idea that they formed as part of a collision in Pluto’s past. Styx was discovered in 2012 as astronomers were using Hubble Space Telescope to search the system for moons and rings around Pluto. It appears to have an elongated shape, and is about 3 by 4.3 miles. Nyx orbits out beyond Styx, and was found in 2006 along with distant Hydra. It’s about 33 by 25 by 22 miles across, making it somewhat oddly shaped, and it takes nearly 25 days to make one orbit of Pluto. It may have some of the same tholins as Charon spread across its surface, but New Horizons didn’t get close enough to get many details. Hydra is the most distant of Pluto’s five moons, and New Horizons was able to get a fairly good image of it as the spacecraft went by. There appear to be a few craters on its lumpy surface. Hydra measures about 34 by 25 miles and takes about 39 days to make one orbit around Pluto. The most mysterious-looking moon is Kerberos, which looks lumpy and misshapen in the New Horizons mission image. It appears to be a double-lobed world about 11 12 x 3 miles across. It takes just over 5 days to make one trip around Pluto. Not much else is known about Kerberos, which was discovered in 2011 by astronomers using Hubble Space Telescope.