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Author Topic: Could our moon........have it's own moon ?  (Read 4975 times)

Offline neilep

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Could our moon........have it's own moon ?
« on: 13/10/2005 16:52:58 »
Yesterday I mooned my wife !..and she noticed that I had a satellite in geostationary orbit...on closer inspection it was something else !!...errhmm...anyway....it got me thinking as to whether our moon could have it's own moon ?

I think it would be tricky as it would have gravitational repercussions  on us and the moon..but, is it possible ?

I'll await your answers, in the mean time i'm going to investigate my own geostationary satellite ;)



Men are the same as women.... just inside out !!


 

Offline Ultima

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Re: Could our moon........have it's own moon ?
« Reply #1 on: 13/10/2005 19:42:12 »
Wouldn't the Earth pull it away from the Moon??? I don't think it would be a stable orbit anyway.... It might be possible with large moons at a large distance from a gas giant, but even then I would have thought any stable system would be some sort of odd binary satellite that orbit each other mutually. I've wondered about this to, so I hope someone with more knowledge gets their typing hand in gear!
 

Dr. Praetoria

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Re: Could our moon........have it's own moon ?
« Reply #2 on: 13/10/2005 21:48:00 »
It would seem that the physics of three or more interacting bodies would be extremely difficult to ascertain.  Could one find a system in which a body would be held equally between two other rotating objects and, perhaps be even stationary?  This post does give rise to an interesting question as to the effect the moon did have in the development of life on Earth due to the moon's stabilizing result on Earth's revolution, permitting seasons that would generate life.  Would the Earth, without the moon have resulted in mainly oceans and could have such water creatures develope intelligence comparable to humans?  Or, in other words, why did humans develope the degree of intelligence we now find?
Doc
 

another_someone

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Re: Could our moon........have it's own moon ?
« Reply #3 on: 14/10/2005 04:10:56 »
This is not only possible, but it has happened, albeit, in a rather artificial context.

During the moon missions, there were a number of artificial satellites that were put into orbit around the moon, before they were pushed out of that orbit and returned to Earth.
 

Offline Titanscape

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Re: Could our moon........have it's own moon ?
« Reply #4 on: 15/10/2005 13:45:43 »
I think it would rapidly decay in orbit and collide with the moon. For at each orbit it would increase velocity in relation the the Earth and decrease. It would cause a wobble. Sometimes a little more escaping Earth orbit sometimes falling lower, but while it orbits the moon. As it would have to orbit in the same plane as the moon. Or do you think it could orbit the moon in a different plane, so that if you could see it, it would not disappear behind half the time bit go from pole to pole?

Titanscape
 

another_someone

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Re: Could our moon........have it's own moon ?
« Reply #5 on: 15/10/2005 14:35:33 »
quote:
Originally posted by Titanscape

I think it would rapidly decay in orbit and collide with the moon. For at each orbit it would increase velocity in relation the the Earth and decrease. It would cause a wobble. Sometimes a little more escaping Earth orbit sometimes falling lower, but while it orbits the moon. As it would have to orbit in the same plane as the moon. Or do you think it could orbit the moon in a different plane, so that if you could see it, it would not disappear behind half the time bit go from pole to pole?

Titanscape



Sorry, I don't say my maths is up to working out the exact complications of such an orbit, but I am a little confused as to where you think it would be gaining or losing the energy that it requires to change orbit?

A low earth orbit decays because energy is lost to atmospheric drag, but this would not be a problem for a low moon orbit.

The only reason I can see for a collapse of the orbit is if there is insufficient inertial energy to maintain orbit.  I could understand that the pull of the Earth may cause a slightly irregular orbit, but this is no different than the very slight irregularities that the gravitation pull of the moon and the Sun would cause upon satellites in orbit around the Earth (or even the inevitable impact that the gravitational pull of the Sun must have on the Moon).

Maybe I am just being dumb, but I cannot see what you are expecting to happen.
 

Offline ukmicky

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Re: Could our moon........have it's own moon ?
« Reply #6 on: 15/10/2005 15:08:26 »
Binary stars can have planets in stable orbits so i can't see why a moon can't have a orbiting moon, i suppose it would all depend on the type of orbit of the first and second moon. But it should be possible

Michael                                      
« Last Edit: 15/10/2005 15:33:24 by ukmicky »
 

Offline Atomic-S

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Re: Could our moon........have it's own moon ?
« Reply #7 on: 21/11/2005 06:17:06 »
Re a moon of the moon:

No such (natural) moon has ever been discovered to my knowledge; however:

The combined earth-moon system offers us the following orbital dynamics: There are four points of gravitational stability, which is to say, positions such that a body located in any of them would be in a state of neutral gravitation with respect to the earth-moon axis, and would therefore have an orbital period with respect to the earth which was the same as that of the moon. Those four places are:  One 60 degrees forward from the moon (measured with the earth as the vertex of the angle) and located within the moon's path;  another 60 degrees backward butotherwise the same; one located along the earth-moon axis but at a position further from the earth than the moon is (I do not know exactly how far); and the fourth is likewise on the earth-moon axis only it exists between the earth and the moon. The two points located + and - 60 degrees from the earth moon axis are points of dynamic stability, I believe; an object slightly perturbed from those positions would tend to return. the other two points may not be: I am not sure. Absolute precision of location may be necessary to stay there, or some compensating mechanism to correct for slight perturbations.

Additionally, my suspicion is that a satellite located quite close to the lunar surface would tend to stay in orbit indefinitely; although if at a substantial distance from it, there could be dynamical problems.
 

Offline Atomic-S

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Re: Could our moon........have it's own moon ?
« Reply #8 on: 21/11/2005 06:21:02 »
quote:
This is a test
 

Offline Jenesis

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Re: Could our moon........have it's own moon ?
« Reply #9 on: 28/11/2005 09:39:35 »
I'm new here (got directed here got by my Physics teacher!), but the first thing that springs to mind when thinking about subsystems within orbits is Pluto. Charon is so big that the two bodies are almost orbiting each other?

Astronauts used to ride rockets with a million litres of hydrogen burning under their seats. D'you think they said "Gee, I'd love to go to the Moon today, but it seems a little risky"?
 

Offline ekc

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Re: Could our moon........have it's own moon ?
« Reply #10 on: 02/12/2005 21:35:42 »
I can think of no reason why a small satellite couldn't orbit the Moon.  It is even possible for a second moon to orbit around both the Earth and Moon if it is sufficiently far out.

By the way, I am not one who likes to recommend books, but there is a short story by Arthur C. Clarke in which lunar orbital mechanics take centre stage.  It's a thriller called "Three Body Problems", and it is unbelievably intense for a tale grounded in hard science...I was sweating by the end of it!
 

Offline ukmicky

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Re: Could our moon........have it's own moon ?
« Reply #11 on: 02/12/2005 23:07:39 »
It is possible as long as the moons satelite orbits in a very elliptical manner, similar to the way a comet orbits the sun.
e.g comes in fast and close and is shot out far BUT in a direction which is away from the planet

Michael                                      
« Last Edit: 02/12/2005 23:08:27 by ukmicky »
 

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Re: Could our moon........have it's own moon ?
« Reply #11 on: 02/12/2005 23:07:39 »

 

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