The farthest planet from the Sun has a rather strange collection of satellites in its orbit. This may be because Triton, Neptune’s largest moon, caused a disturbance billions of years ago when it forced its way into the planet’s orbit. Scientists now suggest that, with one exception, Neptune’s original suite of moons was violently destroyed by Triton’s violent intrusion.
Using data from the Webb Space Telescope, a team of researchers believes that Neptune’s moon Nereid is the only moon that survived the ancient lunar collision that rewrote the history of the planet’s orbital satellites. Recently to learn In a paper published in the journal Science Advances, researchers provide new insights into the solar system’s chaotic history and how it has changed over billions of years.
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Neptune’s moon Triton was discovered just 17 days after the planet itself. It is almost the size of Earth’s Moon, much larger than Neptune’s other moons. Triton orbits in the opposite direction of its planet’s rotation, making it the only large moon in the Solar System to exhibit such strange behavior.
Because of its strange qualities, scientists believe that Triton did not form from the remnants of the formation of Neptune. Instead, it may be a Kuiper belt object that was pulled and captured by Neptune’s gravity about 4 billion years ago. Triton entering orbit around Neptune can cause quite a bit of chaos by disrupting the planet’s satellite system.
Another strange moon orbiting Neptune is the Nereid. The third largest of Neptune’s moons, it has the most eccentric orbit of all the moons in the Solar System. As one of the outermost moons around Neptune, it takes 360 Earth days to complete one orbit around its host planet. Its strange orbit suggests that the Nereid is also captured by Neptune’s gravity.
But new research suggests that rather than sharing a common origin story, Triton and the Nereid may have been enemies for a long time.
Surviving Triton
The researchers behind the study, led by first author Matthew Belyakov of the California Institute of Technology, used Webb’s infrared capabilities to observe the Nereid for just 10 minutes and 40 seconds. They found that the moon is rich in water on its surface and is brighter than many Kuiper belt objects. Instead, the overall Nereid signature was more similar to the moons found around Uranus.
The researchers then ran computer simulations to test whether the Nereid was part of Neptune’s first crew of moons. In simulations where Triton crashed through Neptune’s satellite system, one or more satellites survived in irregular orbits 20% of the time.
The study suggests that Triton’s forced entry into Neptune’s orbit during the Solar System’s first 200 million years would likely have destroyed the planet’s first set of moons. On the other hand, the Nereid may have been rescued and thrown into an eccentric orbit.
This leaves Nereid as the sole survivor of an ancient lunar collision that destroyed its fellow moons and left it further away from its home planet. It’s a hellish story, with young Neptune thrown into chaos by the arrival of Triton and Nereid emerging as the sole survivor of the planet’s original lunar family.
