Can exomoons have moons?

Nov 13, 2020
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As has been a consideration for some time, one of the frontier areas of astronomy especially in research in other solar systems is the search for moons of other planets, exomoons. British astronomer David Kipping has led the way in research that seems to support a very large exomoon around the exoplanet Kepler 1625 b. Kepler 1625 b is a super-Jupiter and its moon or exo-moon Kepler 1625 b i is a Neptune or sub-Neptune mass body. (Of course this moon would then be an order of magnitude more massive than Earth!) Of course this is where some of the dispute of this claim of discovery comes in as we don't have any moon anywhere near that mass in our solar system even around our planet Jupiter that barely has moons the mass of Earth's moon.

But if it is granted that there are exomoons, including the massive one around Kepler 1625 b (or possibly other similiarly massive ones around other super-Jupiters) my question is could or how likely would it be that these exomoons could themselves have moons or natural satellites? How gravitationally stable would the orbits of such moons of exomoons be including in different arrangements of planets, stars and moon masses or orbits or types of stars giant, dwarf or regular or temperature and spectral class? Also, it seems with our current technology clearly detecting moons of exomoons is very difficult. What would be the prospect of detecting sizable moons of large exomoons currently or in the forseeable future with transit, radial velocity, transit timing variation (TTV), direct imaging or other technologies including with the soon to be launched James Webb Space Telescope or fairly soon to have construction completed and go into science operations next generation larger ground based telescopes the Giant Magellan Telescope or the Extremely Large European Telescope?
 
As has been a consideration for some time, one of the frontier areas of astronomy especially in research in other solar systems is the search for moons of other planets, exomoons. British astronomer David Kipping has led the way in research that seems to support a very large exomoon around the exoplanet Kepler 1625 b. Kepler 1625 b is a super-Jupiter and its moon or exo-moon Kepler 1625 b i is a Neptune or sub-Neptune mass body. (Of course this moon would then be an order of magnitude more massive than Earth!) Of course this is where some of the dispute of this claim of discovery comes in as we don't have any moon anywhere near that mass in our solar system even around our planet Jupiter that barely has moons the mass of Earth's moon.

But if it is granted that there are exomoons, including the massive one around Kepler 1625 b (or possibly other similiarly massive ones around other super-Jupiters) my question is could or how likely would it be that these exomoons could themselves have moons or natural satellites? How gravitationally stable would the orbits of such moons of exomoons be including in different arrangements of planets, stars and moon masses or orbits or types of stars giant, dwarf or regular or temperature and spectral class? Also, it seems with our current technology clearly detecting moons of exomoons is very difficult. What would be the prospect of detecting sizable moons of large exomoons currently or in the forseeable future with transit, radial velocity, transit timing variation (TTV), direct imaging or other technologies including with the soon to be launched James Webb Space Telescope or fairly soon to have construction completed and go into science operations next generation larger ground based telescopes the Giant Magellan Telescope or the Extremely Large European Telescope?
I don't see why an exo moon can't have it's own moon.
Orbital mechanics say it's possible then it will exist.
The big planet they orbit will disturb most of what could become a moon of a moon so i have a feeling exo moons will be pretty small Phobos sized beasts or maybe a bit bigger.

We have a lot of moons in our solar system and not one of them has a moon so i bet it's pretty rare in the universe. less than 1 in 1000 or more.
Bigger planet tidal disturbance might not allow it to be stable.

I'm of the opinion earth sized exo moons in the HZ will be 100s of times more likely to have life than just hunting for earth sized planets in the HZ.
Many more of them and in much better stable climate, star protected locations as a moon.
JMO
 
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An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body. It is inferred from the empirical study of natural satellites in the Solar System that they are likely to be common elements of planetary systems. ... To date there are no confirmed exomoon detections.
Yes, overall that's true I think that there haven't been any confirmed exomoon detections. However, I follow Professor David Kipping who is one of the main astronomers in the world searching for and writing about exomoons. He is also the main astronomer claiming there is an exomoon around Kepler 1625 b. He states that one of the reasons that the scientific community hasn't accepted the moon he claims around Kepler 1625 b is that it doesn't fit the usual models thought for exomoons being about the mass of our planets Uranus or Neptune or perhaps a little less and therefore the astronomical community is requiring more rigorous proof of confirmation of this discovery for this reason and that it would be the first confirmed exomoon that if this object didn't have either of these characteristics.
 
Jul 27, 2021
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In our Solar system.
1. Observations of Io, Jupiter moon, that have sparkled the idea, which states that it might have it's moon. As far as it is volcanic activity is very strong and Jupiter pull has a strong influence, in certain conditions an eruption might through the matter enough to stay on orbit.
Though it didn't happen.
2. Cryovolcanoes which are observed within the Solar System, icy moons of, including Europa, Titan, Ganymede, and Miranda are not well explored yet, that may have same effect.

In this case, there is possibility of an exomoon to have a moon.
 
Yes, overall that's true I think that there haven't been any confirmed exomoon detections. However, I follow Professor David Kipping who is one of the main astronomers in the world searching for and writing about exomoons. He is also the main astronomer claiming there is an exomoon around Kepler 1625 b. He states that one of the reasons that the scientific community hasn't accepted the moon he claims around Kepler 1625 b is that it doesn't fit the usual models thought for exomoons being about the mass of our planets Uranus or Neptune or perhaps a little less and therefore the astronomical community is requiring more rigorous proof of confirmation of this discovery for this reason and that it would be the first confirmed exomoon that if this object didn't have either of these characteristics.
We are not to far from getting proof of these exo moons.
Just a bit of time now and the proof one way or another will happen.

A zoo of exo moons is sure to exist with endless earth sized ones that need no big moon to be stable climates.
Fun times ahead for sure.
 
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Catastrophe

The devil is in the detail
Has any moon in the Solar System got a satellite? I cannot think of any.
Perhaps there is a problem in formation, and capture may be more likely by the planet.

Cat :)
 
Has any moon in the Solar System got a satellite? I cannot think of any.
Perhaps there is a problem in formation, and capture may be more likely by the planet.

Cat :)
I don't think any moon in our solar system has a moon.
Probably unstable orbital mechanics for a moon to have a moon.
Got to be a pretty rare happening for a moons gravity to be an exact match against the host planets gravity so a moons moon can exist.
Even an exact match and tidal effects are sure to make a moons moon wander orbit.
 
May 14, 2021
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I agree, the moons in our system are close enough to their primaries that I would think that the planet or companion moons would prohibit moon satellites. There may be a star somewhere that has a distant planet who has a relatively distant moon with a satellite. That would be a cool discovery.
 
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Catastrophe

The devil is in the detail
Yes, if (exo) planets are 30-50 (or more) AU away from their star. I know Pluto is a Dwarf Planet, but it has 5 moons, one of which is a co-planet. That is the nearest I can think of.

Cat :)
 
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Catastrophe

The devil is in the detail
Yes. Have you read the section in "Fundamental Planetary Science" by Lissauer and Pater?
It covers 'reduction of the Two Body Problem to the One Body Problem', 'the Three Body Problem', 'Secular Resonances', et cetera. .

Cat :)
 

COLGeek

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Yes. Have you read the section in "Fundamental Planetary Science" by Lissauer and Pater?
It covers 'reduction of the Two Body Problem to the One Body Problem', 'the Three Body Problem', 'Secular Resonances', et cetera. .

Cat :)
I haven't, but will check it out.

Seems a relatively easy thing to model as well. Heck, it could even be made into a game of sorts.
 
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Maybe I’ll try that in Orbiter simulator see if it works there, sometime. Maybe move Vesta or small asteroid to the moon or large moons, see what happens.
 
I agree, the moons in our system are close enough to their primaries that I would think that the planet or companion moons would prohibit moon satellites. There may be a star somewhere that has a distant planet who has a relatively distant moon with a satellite. That would be a cool discovery.
I think with all the possible setups in the universe moons with moons will happen.
You example of distant orbiting moons might be one way, gravitational tugs IMO will have to still be pretty small or we get into wandering moons of moons.
 
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Yes, if (exo) planets are 30-50 (or more) AU away from their star. I know Pluto is a Dwarf Planet, but it has 5 moons, one of which is a co-planet. That is the nearest I can think of.

Cat :)
Pluto and it's bunch of moons sure is an oddity.
All those moons and little tidal effects and still no moon of a moon.
That is probably telling us it's a very rare thing to be a moon of a moon.
 
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So far at least, no submoons have been found orbiting any of the moons considered most likely to support them – Jupiter's moon Callisto, Saturn's moons Titan and Iapetus and Earth's own moon.26 Jan 2019
Can moons have moons? | Space | EarthSky


Cat :)
Maybe something like pluto's setup would work with 2 big moons nearly the same size orbiting a host planet together.
Tidal effects should be near canceled for that setup and little to no wandering of either?
Wouldn't a double earth sized moons be interesting in that setup :)
 
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COLGeek

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It would take some pretty unique circumstances/distances/masses to prevent the 3rd case satellites to not get "scraped" away by the 1st case planet. Planet(1) <>Moon (2)<>Moon's Moon(3).
 
It would take some pretty unique circumstances/distances/masses to prevent the 3rd case satellites to not get "scraped" away by the 1st case planet. Planet(1) <>Moon (2)<>Moon's Moon(3).
Only really 2 ways i can see moons moons happening without tidal forces from the host making the smaller moon wander.

Two moons of nearly the same size orbiting the host orbiting each other in a central gravity point.
Distant orbiting moon with 2 moons that can counteract tidal forces or the tidal forces are so small they have no real wandering effect on a small moons moon.

Big universe so I'm sure both will exist but i think very rare beasts.
Maybe the double moon setup will be best chance.
 
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IG2007

"Don't criticize what you can't understand..."
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Theoretically speaking, our moon itself had dozens of moons in its history - including the ones we sent there and some random rocks probably lying about.

I mean, like, think of this: Sun has satellites which have satellites of its own, so why can't the satellite of a satellite have a satellite? Consider this fact too: Sagittarius A* has our Sun as a satellite which has Earth has a satellite which has moon as a satellite. :)
 
Theoretically speaking, our moon itself had dozens of moons in its history - including the ones we sent there and some random rocks probably lying about.

I mean, like, think of this: Sun has satellites which have satellites of its own, so why can't the satellite of a satellite have a satellite? Consider this fact too: Sagittarius A* has our Sun as a satellite which has Earth has a satellite which has moon as a satellite. :)
I think it all comes down to tidal effects of the host.
Without a cancelation of them somehow the host will tug on the smaller of moons or moon of moon more than the bigger moon.

Location of what is at what location and size of moons in comparison to each other will have a role.

When you think about it our moon probably has 1000s of mini moons.
As dust specs and tiny objects go are they really moons? and are they stable moons?
Moon definition also needs a new rule on what is a minimal thing to be called a moon.
And what the heck is a moons moon going to be called? :)
 

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