When a moon circles round a planet,is it possible for it also to have a moon going round it. Does this occur anywhere in our solar system.
2006-10-20 21:56:50 · 26 answers · asked by spike 5 in Science & Mathematics ➔ Astronomy & Space
What a fascinating question.
I'd always just assumed it was theoretically possible but rare, but I'm glad to see from the answers that there are real examples. I wish somebody had said which of Jupiter's sixty-odd moons had a companion. According to Wikipedia there are no naturally occuring examples of the phenomenon. There certainly are 'Trojan' moons around Jupiter (ones sharing the same orbit but in at a fixed angle to the companion moon.
The main reason given for the theoretical possibility is the Hill Sphere - the sphere of space around a celestial object which is that object's gravitation sphere of influence. For large rocky satellites the Hill Sphere is correspondingly large. It sounds like an interesting problem in probability working out the likelihood of a lump of passing rock having just the right energy and trajectory to become capture by a satellite rather than its primary.
I wonder if the people who answer so definitely 'no' have taken the trouble to look at any evidence or even have a sound theory on which to base their certainty.
I guess as long as the distances involved are large enough, and the differences in mass as sufficient you could take this on and on with resulting relatively stable system. But the smaller the orbiting object the more likely it is that its orbit will be disrupted by some passing lump of rock.
There are binary star systems - I wonder if you ever get binary planet systems where the two objects are so similar in mass that they really do waltz round a shared point in space.
Really interesting, thought provoking question.
2006-10-21 00:09:39 · answer #1 · answered by Anonymous · 0⤊ 0⤋
The sun also orbits the center of the Milky Way galaxy!
To be more exact, the planet and moon orbit their shared "center of gravity". Look at Pluto and Charon, they rotate around the empty space between them. Because Pluto is bigger, it moves less than Charon. Since the Earth is so much bigger than the Moon, the Earth wobbles a little, since the center of mass is within the Earth's crust, but not exactly at the center of Earth.
Answering your question, short term definate "yes", long-term uncertain. Reason: chaos theory and n-body problem. Look that up sometime. The Earth's orbit is actually chaotic. My guess is planet-moon-moon will only work for certain starting conditions (some cases moons would collide after a period of time). The most likely reason why the planet can still orbit the star (Sun) and have a moon is the distance, which relates to the next topic.
One interesting observation, the smaller object tends to "tidally lock" on the bigger object, with the same side facing the planet. Our moon always has the same side, facing us. However, the Earth does NOT have the same side facing either the moon or the sun. The Earth revolves around the Sun (year), but it's rotation (days) is not locked to the Sun, otherwise one side of Earth would always get day and the other night. The moon affects our ocean tides, even more than the Sun! Mercury is pretty close to tidally locked with the Sun. Most moons are tidally locked to their planets. Pluto and Charon are tidally locked to each other, but not the Sun.
Mercury is not tidally locked to the Sun, but it is in 3/2 spin-orbit resonance with the Sun. Cruithne is also called a second moon of Earth, see the licks below on why. It is in 1:1 resonance with the Earth.
Understanding these concepts will help answer your question. This sounds like a good thesis to earn your Ph.D. with. Good luck finding the answer!
2006-10-20 22:02:08 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Yes, it is technically possible to have a moon of a moon, but it would be a very rare thing.
For starters, it is possible for a moon have another, smaller object orbit around it. If the larger moon was massive enough to have a strong gravity, and the smaller moon was large enough to be treated as an actual moon (as versus just some orbiting rock), then a moon would have a moon.
And to answer the second question - no, it does not occur anywhere in our solar system. It would be difficult for a moon's moon to keep an orbit for long, since the gravity of the planet itself would tend to disrupt said orbit.
2006-10-20 22:18:39 · answer #3 · answered by Gelondil 1 · 2⤊ 0⤋
YES
A moon is a body orbiting a planet or planetoid in a solar system
Both planets and moons can have bodies orbiting them therefore the moon can have a moon by definition.
See earlier answers for where in our solar system they can be found.
2006-10-21 00:51:48 · answer #4 · answered by scrambulls 5 · 1⤊ 0⤋
Yes. Do you recall a little experiment in the late sixties called Apollo, where - if you believe the history books - Americans landed on the Moon? Well, they took a lot of junk with them. Some of it was left on the surface, some of it was jettisoned somewhere between here and there, and some of it burned up on re-entry. There were some bits, however, that were left in orbit around the moon. Owing to the low gravity of the moon, most of it is still up there. I'm not sure of the technical definition of a moon, but the moon is often referred to as a satellite. These pieces of junk are satellites, and therefore moons.
2006-10-20 22:17:38 · answer #5 · answered by Dr Know It All 5 · 1⤊ 1⤋
During the Apollo missions, it was part of the mission for the Command Module to go into lunar orbit. So if the Moon can have an artificial satellite, there's no reason why it's not possible to have it's own natural 'moon'.
2006-10-20 22:32:38 · answer #6 · answered by Feckpot 2 · 0⤊ 0⤋
There are twin lunar systems out there, where the moons are approximately the same size.
I don't know if it's possible for a moon-sized satellite to have a smaller satellite surrounding it and have it called a moon. We're so conditioned to our own moon that it's hard to define what a "moon" is...
2006-10-20 22:27:07 · answer #7 · answered by Anonymous · 0⤊ 0⤋
No. the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon the moon is a moon is a moon.
2006-10-20 21:59:46 · answer #8 · answered by Anonymous · 0⤊ 11⤋
Yes. Think about the earth-moon system; moon orbits the earth (Well, both orbit a common centre of gravity, but what the heck) and the pair orbit the sun!
2006-10-20 22:00:04 · answer #9 · answered by Avondrow 7 · 0⤊ 0⤋
The Moon is a satellite,the first one to circle the Earth,so the answer in no.
2006-10-20 22:08:50 · answer #10 · answered by Anonymous · 0⤊ 1⤋