This question sounds like silly and rather fantasy filled. But can our earth's gravity capture a sizable asteroid and make it rotate around our earth like our moon which become visible from ground. Is there any theoretical possibility or practical probability?
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$\begingroup$ Some silly answers: 1) we could capture an unusually slow comet that came unusually close to our planet, 2) Gamma 2 Velorum might go (or already have gone) supernova, and might approach moon-like brightness for a while (though it wouldn't technically be a moon). 3) the British TV show QI had fun with this question, claiming at different times that the Earth had between 1 and thousands of moons, but none of the other "moons" was visible. And finally, some people now think that our current moon is a planet. $\endgroup$– user21Nov 16, 2015 at 17:26
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1$\begingroup$ earthsky.org/space/asteroids-accretion, or see also astronomy.stackexchange.com/questions/8795/… which covers most of the answer to this. $\endgroup$– James KNov 16, 2015 at 19:49
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$\begingroup$ Why, you don't think just one isn't romantic enough? $\endgroup$– RickyNov 18, 2015 at 6:11
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$\begingroup$ Because more the merrier :) This is just a curiosity, who knows it'll be more romantic to have two of them :) $\endgroup$– Kushal BhuyanNov 18, 2015 at 6:22
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$\begingroup$ @KprimeX: Well, scientifically speaking, it can be easily arranged and would only cost about $100: one needs to pick a starry night, wait for the moon to position itself close to the zenith, toss back ten cognacs in ten minutes, chase them down with a pint of suds, and - voila! $\endgroup$– RickyNov 19, 2015 at 6:20
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2 Answers
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At this stage of our solar system it is impossible for something with size of moon to fall in inner orbit. But smaller things like asteroids do fall in, and become captured by earths gravity. but they aren't big enough to see with naked eye. For example 2006 RH120 is a near earth asteroid which orbited Earth from September 2006 to June 2007.
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1$\begingroup$ I love that diagram, as it shows some of the wierdness that can happen when an object orbits 2 bodies. It's covered in the 2 links above, but it's very difficult in the Earth-Moon (and sun) system for the Earth to acquire a 2nd asteroid for more than a few orbits., There are no stable semi-permanent orbits with so large a Moon and the Sun's influence so strong as well. The Moon is stable, but a 2nd moon wouldn't be. The most stable option is probably a near Earth orbit but that's also the most unlikely to happen naturally and there are Roche Limit problems for an object of any size. $\endgroup$– userLTKNov 16, 2015 at 22:50
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$\begingroup$ how did you generate or get the above picture? any source please. @Kosta $\endgroup$ Nov 17, 2015 at 5:37
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$\begingroup$ Google the name of the asteroid he gave. 2006 RH120 and you'll see similar pictures. Here's an article with a similar, even more exotic movement. npr.org/2012/04/03/149712082/… Since most captured temporary satellites are more distant from the earth than the Moon, the combination of the Earth's gravity, the Sun's gravity (and to a lesser extent, the Moon's gravity), Together that makes for some pretty strange orbital motion, at least in relation to the Earth. In relation to the Sun that squiggle would be mostly elliptical. $\endgroup$– userLTKNov 17, 2015 at 6:52
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$\begingroup$ @KprimeX I found this diagram on Wikipedia page, Here's link en.wikipedia.org/wiki/2006_RH120 $\endgroup$ Nov 18, 2015 at 11:28
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Here's a second and third moon: Telstar 1 and 2.
Telstar 1 and 2—though no longer functional—still orbit the Earth.
Here's a song about Telstar 1. It was a hit for The Tornados back in 1962.
answered Nov 17, 2015 at 18:25