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can moons have moons?

gooddog15

By gooddog15
in Science & Spaceflight

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Motokid600

Motokid600

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Id bet theres a moon of a moon of a moon out there.. somewhere. It just takes so many factors to fall in place correctly. The main factor id say is tidal forces from other bodies. Im sure it happens a lot, but a "stable" orbit is another thing entirely. For instance our moon could have a moon, but it'd be ejected after some time due to the Earth and Sun's gravity. It would take perfect, clockwork resonance for it to be stable. It is possible.

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gooddog15

gooddog15

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Id bet theres a moon of a moon of a moon out there.. somewhere. It just takes so many factors to fall in place correctly. The main factor id say is tidal forces from other bodies. Im sure it happens a lot, but a "stable" orbit is another thing entirely. For instance our moon could have a moon, but it'd be ejected after some time due to the Earth and Sun's gravity. It would take perfect, clockwork resonance for it to be stable. It is possible.

The word "Tidal" just made me think about something about how the lunar mare (dark areas of the moon) formed.

What if it was magma pulled up by the earths gravitational pull?

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gooddog15

gooddog15

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If you think about it, we have the Moon, which orbits the Earth, which orbits the Sun.

By that logic, one more step should be possible.

how about another step, by having moon of a moon of a moon

that could be possible as the asteroid 243 Ida has a moon, and if a asteroid like that goes into one of the "safe zones" of a moon, it would be stable.

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luizopiloto

luizopiloto

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yes... put an asteroid arround one.. so it will have a moon... :P

but real ones, orbits can deteriorate very fast if the gravity fields are not strong and stable enought...

Edited by luizopiloto
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vger

vger

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but real ones, orbits can deteriorate very fast if the gravity fields are not strong and stable enought...

I think it's safe to say that EVERY body that has a significant gravitational field, has a sweet spot. The only problem is whether or not a more massive body, at the right point in time, might have enough influence on the "moon's moon" to muck up its orbit and cause it to crash or escape.

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hugix

hugix

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It depends on the system, but our moon could not carry another moon. The gravitational forces are just to chaotic to pull it out of it's stable orbit.

funny thing is, our moon doesn't even orbit our planet, it orbits the sun and it pulled side to side by the Earths gravity. (Try flying to the moon in Orbiter, halfway you'll notice the suns gravity is more powerful than that of the Earth / moon).

What might be possible is a moon on a planet that orbits a binary system. If the larger star is in in highly elliptical orbit such an orbit could stay stable for a very long time.

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KerikBalm

KerikBalm

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http://en.wikipedia.org/wiki/Double_planet#Definition_of_a_double_planet

It can orbit our planet, and our sun.

anything orbiting at near escape velocity will have the sun "winning the tug of war"

I don't see any value in placing an arbitrary distinction at the ratio of 1:1 , for what constitutes a true moon, or a binary/double planet.

As to the OP's question, I think it would take highly unusual circumstances to result in a stable orbit, but I'm sure there are cases out there

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TerLoki

TerLoki

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Doubtful. I mean, it could probably happen somehow, like how double-planets form only on a smaller scale, but it most likely wouldn't be stable for very long in the grand scheme of things.

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vger

vger

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It depends on the system, but our moon could not carry another moon. The gravitational forces are just to chaotic to pull it out of it's stable orbit.

funny thing is, our moon doesn't even orbit our planet, it orbits the sun and it pulled side to side by the Earths gravity. (Try flying to the moon in Orbiter, halfway you'll notice the suns gravity is more powerful than that of the Earth / moon).

Is the only reason Pluto is able to have so many moons because it's so far away? I mean... wow. Pluto is 1/5th the mass of the moon. Yet the only planets in our system that have more moons than Pluto are the gas giants. Not bad, Pluto. Not bad.

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Motokid600

Motokid600

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The word "Tidal" just made me think about something about how the lunar mare (dark areas of the moon) formed.

What if it was magma pulled up by the earths gravitational pull?

Oh that's exactly what it was. If you look at a pic of the far side of the moon it has no dark areas. As the moon solidified from a molten mass the Earths gravity pulled all that material towards it giving us the those dark areas on one side. This is why the moon is in a tidal lock with the Earth. The moon's entire center of mass was pulled to one side from the Earth's gravity. So if you were to stick the moon in the VAB and switch on the CoM indicator you'd see it's off to one side. So any spin the moon had was slowed with each revolution. In fact I'd put money on saying that the moon actually rocked like a babies crib for a long time before settling.

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Red Iron Crown

Red Iron Crown

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funny thing is, our moon doesn't even orbit our planet, it orbits the sun and it pulled side to side by the Earths gravity. (Try flying to the moon in Orbiter, halfway you'll notice the suns gravity is more powerful than that of the Earth / moon).

I'm not clear what criteria of "orbit" the Moon's relationship to Earth is missing.

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vger

vger

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Exactly. Satellite = moon.

So that would be the Apollo CM. There are currently two US satellites orbiting the Moon - Artemis P1 & P2.

Umm... no.

Moon are satellites, but that doesn't mean all satellite are moons. If they were, then Earth would have upwards of a thousand moons. :sticktongue:

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