Could Earth Support Two Moons in Different Orbits?

In summary, having two moons in a stable gravitational system is possible but depends on the size and distance of the moons. If they are in the same orbit, it is possible if one moon is significantly smaller than the other and can be 60 degrees ahead or behind. If they are in different orbits, it is also possible if the orbits are different enough and the planet is more massive. However, having two Trojans for a moon would require at least three moons in total.
  • #1
petrushkagoogol
28
4
Could we have a stable gravitational system with 2 Moons :

* In the same orbit
* In different orbits ? :wideeyed:
 
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  • #4
In the same orbit: Possible if one moon is much smaller than the other (factor 25 or more). The smaller moon can be 60 degrees ahead or behind of the other moon. Those objects are called trojans. There is also a weird configuration where two moons of similar mass exchange their (very similar) orbits periodically, the Saturn moons Janus and Epimetheus do that.

In a different orbit: yes, if the orbits are different enough. Lighter moons and larger differences lead to more stable systems. A more massive planet far away from the sun helps as well (that's the reason Jupiter and Saturn can have to many moons).
 
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  • #5
The factor of 25 or more refers to the ratio of the total mass of the moons to the mass of the planet. Two trojans can have the same mass.
 
  • #6
Well, two Trojans for a moon would be at least three moons already.
 
  • #7
mfb said:
Well, two Trojans for a moon would be at least three moons already.

can you clarify please ?

are you saying you cannot have 2 Trojans 180 deg from each other ?
that there must be 3 reasonably evenly spaced ?D
 
  • #8
davenn said:
are you saying you cannot have 2 Trojans 180 deg from each other ?
Trojans are 60 degree ahead or behind of the main body. There is nothing 180 degrees apart.

You can have a moon (#1), and a smaller moon (moon #2) as trojan ahead or behind. If you want a second trojan, you are at moon number 3. Which is perfectly fine, but the question was about two moons.
 
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  • #9
mfb said:
Trojans are 60 degree ahead or behind of the main body. There is nothing 180 degrees apart.

You can have a moon (#1), and a smaller moon (moon #2) as trojan ahead or behind. If you want a second trojan, you are at moon number 3. Which is perfectly fine, but the question was about two moons.
ahhhh OK ... wasn't totally sure of the arrangement

thanky
 

1. What is a satellite and what is its purpose?

A satellite is a man-made object that is launched into orbit around the Earth. Its purpose is to collect and transmit data, such as images and measurements, for various purposes including communication, navigation, and scientific research.

2. How do satellites stay in orbit?

Satellites stay in orbit due to a balance between the Earth's gravity pulling it towards the ground and the satellite's forward motion, which creates a centrifugal force that pushes it away from the Earth. This allows the satellite to maintain a stable orbit around the Earth.

3. Can satellites collide with each other?

Yes, satellites can collide with each other in rare cases. This is why it is important for satellite operators to carefully track and monitor the positions of all satellites in orbit and make adjustments when necessary to avoid collisions.

4. How are satellite orbits classified?

Satellite orbits can be classified into three main categories: low Earth orbit (LEO), medium Earth orbit (MEO), and geostationary orbit (GEO). LEO satellites orbit at an altitude of around 500-2000 kilometers, MEO satellites orbit at an altitude of around 2000-36,000 kilometers, and GEO satellites orbit at an altitude of around 36,000 kilometers.

5. How does the orbit of a satellite affect its function?

The orbit of a satellite can affect its function in several ways. For example, a satellite in LEO will have a shorter orbital period and can provide more frequent coverage, but will have a smaller coverage area. A satellite in GEO will have a longer orbital period and a larger coverage area, but will have a delay in communication due to the distance from Earth. The type of orbit also affects the amount of fuel needed for the satellite to maintain its position, and the level of radiation exposure the satellite will experience.

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