Nereid: Neptune’s Ancient Survivor

Scientists announced that Neptune’s moon Nereid might be one of the few original moons of the planet to have survived after a cosmic collision event. With 16 known moons orbiting Neptune, the planet’s largest moon, Triton, is believed to have disrupted the original moons, forcing them into collision paths.

The investigation team, from the California Institute of Technology, employed NASA’s Webb Space Telescope to examine Nereid. Findings suggest that unlike the intruding Triton, Nereid is an original satellite, enduring through its extreme elliptical orbit around Neptune.

What we know about Nereid is very limited. For its size, Nereid is extremely understudied, commented Matthew Belyakov from Caltech.

Nereid’s discovery dates back to 40 years before Voyager 2’s 1989 flyby of Neptune, credited to Dutch astronomer Gerard Kuiper, who named it after Greek sea nymphs. Measuring around 220 miles (350 kilometers) in diameter, Nereid orbits Neptune in nearly a year on an elongated path. It swings from just under 1 million miles (1.4 million kilometers) to 6 million miles (9.6 million kilometers) away from Neptune.

Nereid, suspected of originating from the Kuiper Belt, was found inconsistent with Kuiper Belt objects due to its icy composition as revealed by the Webb telescope. This points to its formation within Neptune’s system.

We don’t have all that much evidence left around Neptune – the system doesn’t have many moons left, stated Belyakov. He highlighted that current observations strongly negate the idea of Nereid being randomly captured by Neptune.

According to Carnegie Science astronomer Scott Sheppard, who was not involved in the study, this research marks a significant development. He emphasizes that Nereid’s orbit corresponds with the history typical of a moon originating near Neptune. He believes it later moved outward due to Triton’s capture.

Belyakov and his team propose that Neptune’s inner moons may have formed from the debris of Triton’s destructive aftermath. In contrast, Neptune has fewer moons, while other giant planets like Saturn have far more, with 292.

Future missions could reveal more about Neptune’s moons, although none are currently in the pipeline.