Styx MoonEdit
Styx Moon is a small natural satellite orbiting the dwarf planet Pluto. Together with its larger siblings, Styx helps round out the compact system that orbits one of the most distant and least understood members of the Kuiper belt population. Discovered in the early 2010s through observations with the Hubble Space Telescope, Styx was given its mythological name by the International Astronomical Union to reflect the convention of naming Pluto’s moons after figures and places associated with the underworld in classical lore.
Styx is among the smaller moons of Pluto, and it is notable for its place in the chain of bodies that circle the dwarf planet at increasing distances. While Charon is the dominant moon and lies closest to Pluto’s barycenter, Styx sits farther out and is surrounded by a family of even smaller moons, including Nix (moon), Kerberos (moon), and Hydra (moon). The small-moon system around Pluto offers a natural laboratory for studying how satellite systems form and evolve in the outer Solar System, far from the warmth and radiation of the Sun.
Discovery and naming
Styx was identified as a distinct moon in data gathered by the Hubble Space Telescope in the early 2010s as part of a dedicated search for additional satellites of Pluto. Its provisional designation was S/2012 P 1 before it received an official name. In 2013 the IAU approved the name Styx, drawn from the river Styx of Styx (mythology) and aligned with the broader naming scheme for Pluto’s moons—often connected to underworld figures and places. This naming convention mirrors the cultural tradition of linking distant celestial bodies to human myths, and it helps communicate the sense of scale and distance involved in the Pluto system.
Physical characteristics
Styx is a small, irregularly shaped body. Its exact size is not sharply resolved by the available imagery, but estimates place its diameter on the order of tens of kilometers, making it one of the tiniest confirmed moons in the Pluto system. The surface is thought to be a mix of ices and rocky material, with a relatively low albedo typical of many outer Solar System bodies. Because Styx is small and distant, it has not been the subject of a dedicated spacecraft flyby, and most of what is known comes from remote sensing data collected by telescopes and by interpretation of Pluto’s satellite system as a whole.
Orbit and dynamics
Styx orbits Pluto at a distance that places it well beyond Charon yet within the inner portion of the Pluto satellite system. Its orbital period is on the order of a few tens of days, with a fairly low orbital eccentricity and an inclination that keeps its path close to Pluto’s equatorial plane. The ensemble of Styx, Nix, Kerberos, and Hydra forms a compact, near-resonant configuration with Charon that has attracted attention for what it reveals about the formation and long-term stability of the system. The prevailing view is that these moons likely coalesced from the debris of a cataclysmic event in Pluto’s early history—a giant-impact scenario that produced a disk from which multiple moons accreted. This scenario helps explain the near-cooperative orbital relationships among the small moons and their relatively regular orbital spacing.
Formation and evolution context
The Pluto-moon system, including Styx, sits in a region of the Solar System where collisions and gravitational interactions can sculpt compact satellite families. The leading formation model posits that a large impact in Pluto’s distant past ejected material into orbit around the planet, forming a disk from which Styx and its siblings accreted. This model also accounts for the dynamic interplay among the moons, including their resonant-like orbits and the overall stability of the system over long timescales. Studying Styx thus informs broader questions about how satellite systems assemble around icy dwarfs and how such systems endure in the outer Solar System.
Observational history and current status
Direct visits by spacecraft to Styx have not occurred; however, the Pluto system has been scrutinized in detail by the New Horizons mission, which conducted a historic flyby of Pluto in 2015 and provided high-resolution imaging and data about Pluto and its moons. While New Horizons did not perform close maneuvers for Styx specifically, the mission significantly advanced understanding of the system’s geometry, mass distribution, and surface compositions. Ongoing analyses of telescope data continue to refine estimates of Styx’s size, shape, and reflectivity, contributing to a more complete picture of how Styx fits into the Pluto system.