NASA – With the New Horizon probe approaching the dwarf planet of Pluto, scientists are learning more and more about the celestial object that’s roughly 3.7 billion miles away from Earth. But while we wait for New Horizon to reach Pluto, scientists are using information from the Hubble telescope to learn more about Pluto’s moons.
Pluto and Charon, its largest moon, orbit a shared center of mass that’s due to their mutual gravitational influence on one another. Four other moons, Styx, Nix, Kerberos, and Hydra, also orbit this common gravitational center, and not Pluto itself. This is a distinct difference from the other moons in the solar system, as these moons tend to wobble in near-circular orbits.
This oddity of Pluto’s moons continue to confuse scientists with regard to how this distant set of celestial objects originally formed. Most believe that at some point a large object crashed into Pluto, with the moons forming from the debris, but what transpired after that is still a mystery.
New evidence collected from Hubble supports the impact theory, as there is reason to believe that Styx is locked in orbital resonance with Nix and Hydra, meaning these bodies exert gravitational influence on one another, creating a predictable pattern in their orbits. However, while these moons appear to be locked in resonance, Nix and Hydra are sometimes disrupted and thrown into chaos without a known cause.
The binary relationship between Pluto and Charon may cause the non-spherical moons of Nix and Hydra to have chaotic rotations, which supports the impact theory for the formation of this group of celestial bodies. However, the moon Kerberos does not fit the impact theory due to the fact that it does not have similar size and brightness with the rest of Pluto’s satellites.
Scientists are hoping to gain clarity when New horizon reaches Pluto on July 14. The probe should shed some light on the darkness of Kerberos, the orbital mechanics of Pluto and its satellites, and the possible existence of any other moons or rings under Pluto’s gravitational pull.