Earth second moon?

[cziken20]

I know that we have only one moon- but is it possible for Earth to capture an asteroid and have second moon?

It would be very nice feeling to look for it in sky

[sickboy]

Correct me if I'm wrong, I'm not as good at real physics than Kerbal's but to enter our SOI and somehow get into orbit around Earth, wouldn't that asteroid need to enter our atmosphere, a-la-aerobraking?

that could be very bad depending on it's size

[cynar]

In theory, yes. In practice, it would likely be highly unstable due to the moon's and the sun's gravity. It would either be flung out of the earth moon system, or crash into one.

As for capture, the most likely method is via a gravity slingshot off the moon, it might even enter an orbit that is stable for 100s of years, but that is unlikely.

The exception is if it gets caught in one of the Lagrangian Points. L4 and L5 are stable and so could trap an asteroid. There is also evidence that one might be there already.

[Comrade Jenkens]

Maybe a reverse slingshot around the moon that slows it down?

[Kermunist]

Here's an example of the real-life track of an object that was captured by earth

http://en.wikipedia.org/wiki/File:J002e3f_orbit.gif

As you can see, the interactions with the moon result in a very non-KSP-like non-simple orbit, and after about 6 orbits it is ejected again.

Any capture probably involves a reasonably close encounter with the moon or the upper atmosphere. Given the nature of orbits, if it has one such encounter, sooner or later it will have another, and at some point it will hit earth, or be ejected. It might hang around for a while, but it is very unlikely to ever enter a fully stable orbit.

[K^2]

Yeah. The main problem is that anything that enters the system via Moon gravity assist would be greatly influenced by the moon thereafter, so it will likely be flung out of the system.

The only exception I can think of is if a binary asteroid/comet enters the system, with one of the pair getting captured. That can happen with a much gentler assist from the Moon-Earth system, which can allow the captured asteroid to stay far enough out to remain stable for a long time. Earth's Hill Sphere can accommodate a body in 1:2 resonance with Moon-Earth system. That can allow a captured asteroid to go from the initial capture orbit to a stable near-circular orbit in the system.

The odds against that are astronomical, of course, but it's not impossible.

[Jacob01]

I think its possible, but unlikely. As others have said, its likely to be ejected not so long after it was captured. Perhaps, if something hit the Moon, it could break up to form multiple other moons. I'm not sure if that would work though, the debris might just form rings, clump back together, get ejected, or hit the Earth.

I think over time, a few small asteroids have been captured and ejected from the Earth's SOI.

Edited January 23, 2014 by Jacob01

[Kerbin Dallas Multipass]

Wikipedia has a whole article on the subject http://en.wikipedia.org/wiki/Other_moons_of_Earth

[stupid_chris]

Yeah. The main problem is that anything that enters the system via Moon gravity assist would be greatly influenced by the moon thereafter, so it will likely be flung out of the system.

The only exception I can think of is if a binary asteroid/comet enters the system, with one of the pair getting captured. That can happen with a much gentler assist from the Moon-Earth system, which can allow the captured asteroid to stay far enough out to remain stable for a long time. Earth's Hill Sphere can accommodate a body in 1:2 resonance with Moon-Earth system. That can allow a captured asteroid to go from the initial capture orbit to a stable near-circular orbit in the system.

The odds against that are astronomical, of course, but it's not impossible.

That is the most probable possibility of a long lasting capture. Anything else would likely be very unstable.

[NASAFanboy]

From what I heard, Earth has several asteroid moons (And the big one), so its possible.

[hugix]

Here's an example of the real-life track of an object that was captured by earth

http://en.wikipedia.org/wiki/File:J002e3f_orbit.gif

As you can see, the interactions with the moon result in a very non-KSP-like non-simple orbit, and after about 6 orbits it is ejected again.

Any capture probably involves a reasonably close encounter with the moon or the upper atmosphere. Given the nature of orbits, if it has one such encounter, sooner or later it will have another, and at some point it will hit earth, or be ejected. It might hang around for a while, but it is very unlikely to ever enter a fully stable orbit.

This is actually quite a funny object. It turns out (with some degree of error) that J002E3 is actually the spend third stage of the Apollo 12 moon mission.

[Mach_XXII]

This is actually quite a funny object. It turns out (with some degree of error) that J002E3 is actually the spend third stage of the Apollo 12 moon mission.

On 14 September 2006 (J002E3) an at 5 meters in diameter was discovered in near-polar orbit around Earth. Originally thought to be a third stage Saturn S-IVB booster from Apollo 12, it was later determined to be an asteroid and designated as 2006 RH120. The asteroid re-entered Solar orbit after 13 months and is expected to return to Earth orbit in 21 years.

[jwenting]

On 14 September 2006 (J002E3) an at 5 meters in diameter was discovered in near-polar orbit around Earth. Originally thought to be a third stage Saturn S-IVB booster from Apollo 12, it was later determined to be an asteroid and designated as 2006 RH120. The asteroid re-entered Solar orbit after 13 months and is expected to return to Earth orbit in 21 years.

IOW it's not in orbit around the earth but in an orbit around the sun that intersects the earth's SOI every few decades and then gets twisted. Few iterations of that and it throws itself out of earth orbit permanently.

[Nuke]

theres also this, but its not a true moon

http://en.wikipedia.org/wiki/3753_Cruithne

good place to place a space colony though.

Edited January 24, 2014 by Nuke

[minerman30]

Someone could also try to use the Min to get into orbit around Kerbin to see if this is possible.

[deadshot462]

Someone could also try to use the Min to get into orbit around Kerbin to see if this is possible.

It is possible and has happened quite a few times when returning from an interplanetary flight. The orbit is definitely not permanent because the ship either eventually gets back in Mun's SOI, hits the Mun, or gets thrown out by the Mun again.

Thinking about it, Ike tends to get you into Duna orbit with the right maneuvers.

[minerman30]

I see.

I wonder what the statistical probabilities are for something like this to happen.