The planet Neptune was first discovered
in 1846 and just several weeks later an English astronomer (and perhaps classic cars enthusiast )called Willian Lassell spotted Triton, a moon with a very peculiar
orbit indeed! All the major moons in our solar system rotate in the
same direction as the planet that they belong to, but Triton alone
goes in the opposite direction, which has led to
speculation that Triton was not formed at the same time as Neptune
but developed elsewhere and was trapped by Neptune's gravity.
Neptune itself was named after the Greek sea god Poseidon (Neptune
is the Roman name for Poseidon) and Triton was one of the sons of
Poseidon so it was an apt name for the moon.
Another strange thing about Triton is that it rotates around its own
axis in exactly the same time as it rotates around Neptune, and this
means that the same face points towards Neptune all the time.
Hardly surprisingly very little was known about a moon which is such
a huge distance away from Earth until Voyager 2 flew within 25,000
miles on it in 1989, and it was found to measure roughly the same
size as our Earth Moon but it appears to be composed mainly of water
ice covering a rocky core with the surface covered by solid nitrogen
and methane; it is pretty darned cold on Triton! There is still a
thin atmosphere, despite this, of mainly gaseous nitrogen and dark
streaks on the surface indicate the presence of winds, although just
how these are formed remains a mystery at present.
So how did this mysterious object get there in the first place?
The currently accepted theory is that it came from the outer solar
system and, travelling a little too close to Neptune, was slowed
down by drag from Neptune's atmosphere, or, possibly, by a collision
with a smaller moon. This could have placed it in to a highly
elongated orbit around the planet, with the gravitational effects of
both of them gradually dragging it into a circular orbit over a very
long period of time. This must have been a very traumatic period for
both the planet and the moon as the gravitational forces would have
been likely to have generated immense heat. This could have been the
reason why Triton appears to have a very dense core and lighter
materials around the outside since this would have occurred
naturally had it been a molten body.
Out of this world - my
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