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I am just an space enthusiast and not a physics professional so pardon me if this is not the right place to ask.
As title says, is there a chance for our Earth to have additional satellite(s) like our Moon? I tried to google it, without luck, however I know here there are very smart people that can perhaps give me some references to read or can give me an answer :)
Thanks

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Hum may I ask why the downvote, question is valid for a physics enthusiast. I invite the downvoter to explain his reasons... –  camiloqp Mar 10 '11 at 17:38
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3 Answers 3

up vote 2 down vote accepted

It's very unlikely. Even if a large body passed near the Earth, it would be on a hyperbolic orbit -- that is, it would have too much kinetic energy to be captured into an elliptical orbit around the Earth. In order to get a new permanent satellite, you'd need a three-body interaction: something would have to come close to the Earth, then, via an interaction with another body, lose enough energy to stay around.

In the early days of the Solar System, there was a lot of junk flying around, so events like this could happen. Nowadays, when things have been largely cleaned out, such a three-body interaction is very improbable.

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""such a three-body interaction is very improbable."" And we should very happy with this . That three-body interaction would be very dangerous for the whole earths surface. –  Georg Mar 10 '11 at 15:49
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The chances for this are not terribly good. There is no current natural satellite around the Earth, unless it is some very small asteroid or meteoroid. There are some near Earth orbiting asteroids which are in resonant “hunter chaser” orbits with the Earth. These are orbits which transfers some orbital energy (energy of angular momentum) of the body to the earth and visa versa. It is a version of the orbital dynamics which permits spacecraft to have a “delta-v” so they can travel to the far outer or inner solar system where our launch craft can’t reach. There are a couple of upper stages from the Saturn V rocket, which were not directed into the moon, that are in such orbits with the Earth.. These objects may impact the Earth or the moon, or may in the future enter into an orbit around the Earth. The two small moons around Mars may have been captured this way.

We humans might decide to adjust the motion of an asteroid so it is in geosynchronous orbit. If we end up building this rather improbable thing called the space elevator, we may find it preferable to build it from “top down,” rather than lifting things from Earth in a bottom up process.

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I would add that the gravitational equations allow it, but humanity will have a collective heart attack if a comet or a large asteroid headed this way, and would probably scramble to control the path long before it came within capture range.

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Bit offtopic, but how much can we control the path of a large asteroid coming? Are we really capable nowadays? It should be something planned like seriously? –  camiloqp Mar 10 '11 at 15:34
    
an H bomb would give enough energy to change a collision path, and it is possible to do it now. As space technology progresses maybe even some sort of propulsion could be devised. –  anna v Mar 10 '11 at 15:51
    
@camiloap here is an article in Wiki en.wikipedia.org/wiki/Asteroid_impact_avoidance –  anna v Mar 10 '11 at 16:49
    
Thanks Anna, very Interesting!! –  camiloqp Mar 10 '11 at 17:50
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