Nereid: Neptune’s Boomerang Moon With Eccentric Trajectory

MessageToEagle.com – Many moons in our Solar System have very special characteristics.

One of them is Nereid, Neptune’s third largest moon located behind Triton and Proteus.

View of Nereid obtained by Voyager 2 on Aug. 24, 1989 at a distance of 4.7 million kilometers (2.9 million miles). Image credit: NASA/JPL/Voyager 2
View of Nereid obtained by Voyager 2 on Aug. 24, 1989 at a distance of 4.7 million kilometers (2.9 million miles).
Image credit: NASA/JPL/Voyager 2

It has a diameter of approximately 340 kilometers (211 miles) and its most interesting characteristic is that it has the most fluctuating orbit of any moon in the Solar System!

Its orbital period is 360.16 Earth days and the age of this moon is estimated to be about 4.5 billion years.

See also:

Miranda: Probably The Strangest Of Uranus’ Moons 

Cosmic Mystery – What Happened To Earth’s Second Moon?

Cosmic Mystery – What Huge Object Caused The Hole In One Of Saturn’s Rings?

More About Astronomy

Nereid is an irregular satellite orbiting Neptune in a very eccentric and inclined orbit, varying from 9.65 million kilometers (6 million miles) away from the planet to just 1.37 million kilometers (854,000 miles) at its closest position.

It was discovered by Dutch-American astronomer Gerard Kuiper, in 1949, while he was working at the McDonald Observatory in Texas.

Neptune and its moon Nereid

Over the years, researchers have also reported Nereid’s unusual brightness according to observations conducted in different periods of time, also from night-to-night.

Nereid is the second of Neptune’s moons to be discovered (and last moon of Neptune to be discovered before the arrival of Voyager 2).

Why is Nereid’s Orbit Eccentric?

Astronomers have long tried to solve a mystery of Nereid’s eccentric trajectory.

Distant Moons of Neptune Orbital parameters for several of Neptune's more distant moons. Image credit: NASA
Distant Moons of Neptune. Orbital parameters for several of Neptune’s more distant moons. Image credit: NASA

According to one theory, the satellite might be an asteroid captured from the Kuiper asteroid belt in the outer Solar System, which could easier explain its unusual orbit.

It is also possible that Nereid was once an inner moon and was perturbed during the capture of Neptune’s largest moon Triton.

However, to learn much more about Nereid is not any easy task for astronomers.

It is difficult to make astronomical observations of a dark moon Nereid. This celestial body has a surface, composed mostly of ice and silicon, which means it reflects only 14 percent of sunlight it receives..

It is extremely faint and Voyager 2 was only able to take a low-resolution image of it when it passed in 1989.

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References:

NASA

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