A recent study by the Weizman Institute of Science in collaboration with the Southwest Research Institute suggests that Neptune’s largest moon, Triton,might have disrupted a primordial satellite system around the ice-giant.
For a long time, scientists suspected Triton to having been captured, rather than accumulated like the other moons of Neptune, since it’s so big, inclined, and orbits the planet retrograde; they assumed Triton actually formed in the Kuiper Belt as a binary and was captured by Neptune’s gravity when it passed by.
For the study, the team ran simulations to determine how the moon’s arrival would have altered the previous system; those were based on disruption scaling laws which considered how non-hit-and-run impacts between Triton and the other moons would have led to the distribution of matter in the sub-system; they found, after 200 simulations, that the system which had a mass ratio similar to the Uranian system or smaller would most likely have produced the current sub-system of Neptune. They also found that the interaction of Triton with this system offers an explanation for how the moon’s initial orbit might have been decreased to preserve the orbits of small, irregular satellites, like Nereid, which would have been ejected out of their orbits otherwise.