[another_someone]

How easy is it to create a natural moon?

The current speculation is that our moon was formed in a collision between another space object (probably the size of Mars) and the Earth throwing matter up and into orbit around the Earth.

It was pointed out (in http://www.thenakedscientists.com/forum/index.php?topic=1333.msg11750#msg11750) that matter ejected from the surface of the planet will generally either fall back to that planet, or keep going for ever, but is not easy to get into orbit.

The other way of obtaining a moon is to capture an existing space object into orbit around the planet.

We (the Earth) have one moon, that was created very early on in the history of the Earth.  As far as I know, we have neither thrown up, nor captured, any other satellites (aside from man made ones) in all of the history of this planet.

Clearly, creating natural moons is a rare event – how likely is it that we will ever get another natural moon (however small) at some time in the future?  Is it at all feasible, whether probable or improbable or impossible?

[syhprum]

I would expect that whenever the Earth is struck by a sizable meteorite some of the ejected materiel will go into orbit and technically could be classed as natural mini moons although unless the meteorite is very large they presumably soon decay.

[DoctorBeaver]

Would it be possible for a NEO, such as a passing asteroid, to be captured by Earth's gravity and sent into an orbit around us? I appreciate that most of them are travelling too fast; but is it feasible?

[syhprum]

It is well known that a planet the virtual twin of the Earth travels in a similar orbit to the Earth but displaced by 180° (some spoilsport astronomers dispute this)so that it is always behind the Sun.
If the orbit of this doppleganger world was disturbed by a large meteorite is it not possible that it would drift around and join the Earth/Moon system as a trio.

[DoctorBeaver]

It is well known that a planet the virtual twin of the Earth travels in a similar orbit to the Earth but displaced by 180° (some spoilsport astronomers dispute this)so that it is always behind the Sun.
If the orbit of this doppleganger world was disturbed by a large meteorite is it not possible that it would drift around and join the Earth/Moon system as a trio.

Well known by whom? If such a planet existed it would be evident from wobbling of the sun. To the best of my knowledge no such wobbling has ever been detected.

In any case, if a planet of that size came close to the earth I'm pretty sure there would be a collision rather a joining as a tri-system.

[syhprum]

See http://www.whirligig-tv.co.uk/tv/children/bumblies/bumblies.htm

[DoctorBeaver]

And here are their neighbours



*photo c/o the BBC

[paul.fr]

And here are their neighbours



*photo c/o the BBC

Doc, i was  thinking of this programme the other day. but could not remember what it was called, was there also a dragon in it? or am i thinking of another programme?

[dentstudent]

It's the Klangers and that would be the Soup Dragon - one of my all-time fave's!

[paul.fr]

It's the Klangers and that would be the Soup Dragon - one of my all-time fave's!

i thought it was the soup dragon, but googling soup dragon just gave me a musical band, i supose that was googles "clanger"

[DoctorBeaver]

It's the Klangers and that would be the Soup Dragon - one of my all-time fave's!

i thought it was the soup dragon, but googling soup dragon just gave me a musical band, i supose that was googles "clanger"

oh groooaaaan  []

[syhprum]

Apologies I confused the planet Bumble with the doppleganger planet as depicted in this film
http://www.imdb.com/title/tt0064519/

[DoctorBeaver]

Apologies I confused the planet Bumble with the doppleganger planet as depicted in this film
http://www.imdb.com/title/tt0064519/

That's no excuse  []

[syhprum]

it is interesting to consider whether the the planet 'Bumble' could exist as a satellite of our moon in a selenstationary orbit, taking Gsmolins figures for the ground level obital time for the moon (108.29 mins) and applying Keplers 3/2 power law gives the height of a 28 day orbit as 88'128 Km not very stable if you consider the disturbing effect of the Earths gravity.