Styx (moon)

Styx is a small natural satellite of Pluto whose discovery was announced on 11 July 2012. It was discovered by use of the Hubble Space Telescope, and is the smallest of the five known moons of Pluto. It was imaged along with Pluto and Pluto's other moons by the New Horizons spacecraft in July 2015, albeit poorly with only a single image of Styx obtained. Styx is the second-closest known satellite to Pluto, and the fifth discovered. It was discovered one year after Kerberos. Styx is approximately across its longest dimension, and its orbital period is 20.1 days. Styx was discovered by a team led by astronomer Mark R. Showalter, using fourteen sets of images taken between 26 June and 9 July 2012 by the Wide Field Camera 3 fitted to the Hubble. The discovery was announced on 11 July 2012. Styx is about half as bright as the dimmest previously known object in the system, Kerberos, and about one hundred thousandth as bright as Pluto. It was designated S/2012 (134340) 1, and informally referred to as P5. The survey work leading to the discovery of Styx was in preparation for the mission of the uncrewed New Horizons spacecraft, which flew by the Pluto system on 14 July 2015. The discovery of another small Plutonian moon heightened concerns that this region of space may harbor more bodies too small to be detected, and that the spacecraft could be damaged by an uncharted body or planetary ring as it traversed the system at a speed of over 13 km/s. Tiny moons, such as Saturn's moon Pallene, tend to be associated with tenuous rings or arcs, because their gravity is unable to hold on to material ejected by meteoroid impacts and such diffuse material represents the chief navigational hazard. However, the New Horizons spacecraft did not detect any smaller moons or rings and it passed through the Pluto system safely. The unexpectedly complex moon system around Pluto may be the result of a collision between Pluto and another sizable Kuiper belt object in the distant past.