Why do planets form?

[ensonik]

I posted this in another thread without response, so I'll try again:

 

What is the current explanation for why random particles within a nebula would in fact be drawn together towards an empty spot in space to eventually form a planet? What is the "motivation" so to speak for random particles to form together at some arbitrary point?

[muhali3]

Maybe dark matter or dark energy. That's what most scientists believe holds galaxies together, so it could also be true for planets. However, i don't know too much on the subject so i could be completely wrong.

[ensonik]

So you're saying the gravitational pull that 'hotspots' of dark matter produce could be the foundation on which planets are based? Interesting theory, I'm not sure if there's any truth to it or not. I guess the implication of that would be that planets, including Earth, reside on high concentrations of dark matter.

[FCA/DP]

I always thought that planets were made simply by the rings of dust from star formation colapseing under its own gravity to form a seed which could be built upon by collisions with other dust particles. But like you I don't know much about the subject so i could be completley wrong also.

[syntax252]

The way it was explained to me is that in a cloud of dust, created by a (the) big bang, and in a vacume (or close enough) that two particles would be attracted to one another because of the attraction between masses. This would create a larger particle of dust which would in turn attract other particles and over a great deal of time, clumps of dust would be formed, which, upon comming close to each other would also tend to be attracted to each other, again, because of the attraction between masses, and that would form even bigger clumps.

 

Sounds a little like making a snowman, doesn't it?

 

Anyway this guy on the other stool says that through the building process planets are formed and the bigger they are, the more stuff they attract, the faster.

 

Now, if they are lucky, and if they are moving at just the right speed, they will wind up orbiting a larger body instead of just flying off into space, or colliding with said larger body.

 

Apparently we (Earth) was lucky .

[ensonik]

always thought that planets were made simply by the rings of dust from star formation colapseing under its own gravity to form a seed which could be built upon by collisions with other dust particles.

 

That makes sense as I could imagine a dust ring having areas denser then others. I suppose these dense areas could ultimately be drawn together, or collapse as you say.

 

The way it was explained to me is that in a cloud of dust, created by a (the) big bang, and in a vacume (or close enough) that two particles would be attracted to one another because of the attraction between masses. This would create a larger particle of dust which would in turn attract other particles and over a great deal of time, clumps of dust would be formed, which, upon comming close to each other would also tend to be attracted to each other, again, because of the attraction between masses, and that would form even bigger clumps.

 

Sounds a little like making a snowman, doesn't it?

 

So I guess my next question would be then, why is this process not continually occurring? If particles within a dust cload are naturally drawn together, should we not be seeing this clumping action take place right now all over the visible universe?

[syntax252]

That makes sense as I could imagine a dust ring having areas denser then others. I suppose these dense areas could ultimately be drawn together' date=' or collapse as you say.

 

 

 

So I guess my next question would be then, why is this process not continually occurring? If particles within a dust cload are naturally drawn together, should we not be seeing this clumping action take place right now all over the visible universe?[/quote']

 

Well, my guess would be that most of the dust has already "clumped up" and what is left probably is clumping up but we ain't out there in space to observe a clump the size of a marble forming every thousand years or so.

[ensonik]

Well, my guess would be that most of the dust has already "clumped up" and what is left probably is[/b'] clumping up but we ain't out there in space to observe a clump the size of a marble forming every thousand years or so.

 

lol

[muhali3]

This "clumping" theory was what i was thinking before, but it would not make sense in some instances. What if, for example, all the particles in a nebula had the same weight, how would something be formed if all had the same gravity? I thought of it like that, so i concluded dark matter/energy. But in many circumstances this "clustering" is much more probable and plausible.

[Rasori]

How would a gas giant be formed via the clumping theory? Just a question, because the theory is plausible. I don't know much about the gas giants.

[muhali3]

Maybe in gas giants, if the gas got any closer together it would bond or something. So maybe gravity isn't strong enough to compress gas to that limit, or the atoms don't have enough electronegativity to form a bond? That could also explain why they are "giants".

[[Tycho?]]

That makes sense as I could imagine a dust ring having areas denser then others. I suppose these dense areas could ultimately be drawn together' date=' or collapse as you say.

 

 

 

So I guess my next question would be then, why is this process not continually occurring? If particles within a dust cload are naturally drawn together, should we not be seeing this clumping action take place right now all over the visible universe?[/quote']

 

Well it is. It just requires certain conditions, namely nebulae. Jupiter is still pulling in comets and stuff, its just that there isn't a lot of stray matter in our solar system, and that which remains is mostly in orbits nicely seperate from other things.

[coquina]

As the solar system formed, the gravity of the sun drew in the heavier, more dense chunks of planetary dust - that is why the inner planets, Mercury, Venus, Earth, and Mars, are rocky. And the outer ones are composed of gas.

[Stumblebum]

Interesting. This suggests that the likelihood of finding gas giants close to a star are remote at best. Do you think the sun had rings like Saturn at one time? Are there any stars known to have rings?

[ensonik]

As the solar system formed, the gravity of the sun drew in the heavier, more dense chunks of planetary dust - that is why the inner planets, Mercury, Venus, Earth, and Mars, are rocky. And the outer ones are composed of gas.

 

So you're saying the planets are ordered outwards from the sun based on their density/heaviness? So Mercury is the second heaviest thing in the solar system next to the Sun, Venus the third, etc?

[Noshi]

gas is collected, and it starts to spin, with the center pulling certain particles, thus former a protosun, then rings start to slowly former , size of the sun and the amount of particles determines the rings, then the rings start to form into protoplanets, until the planets form, then the planet might get moons in a similar method, this is the one we were explain in physic - astronomy in university, of course I simplyfied it, also a reason for this belief is the asteriod belt is beleived to have failed the process, thus leaving a belt of asteriods

[coquina]

gas is collected, and it starts to spin, with the center pulling certain particles, thus former a protosun, then rings start to slowly former , size of the sun and the amount of particles determines the rings, then the rings start to form into protoplanets, until the planets form, then the planet might get moons in a similar method, this is the one we were explain in physic - astronomy in university, of course I simplyfied it, also a reason for this belief is the asteriod belt is beleived to have failed the process, thus leaving a belt of asteriods

 

Noshi -

Thanks, that is what I remember reading, but you explained it much more thoroughly.

[Vladimir]

Dust Rings? Dense Pockets? Its just an accumualation (pardon spelling) of rock. One piece collides with another, the two become stuck, this happens too numerous pieces of rock, unitl eventually they then collide, some bits break off, and the cycle starts again for the bit that broke off, the now larger piece gains larger and larger amounts of rock until gravity begins to take a noticeable effect upon it. All this bussiness with nebulae and denser pockets of rings?! Nebulae are gaseous.

[Molotov]

http://www.spacedaily.com/news/early-sol-05a.html

explains how meteorites may have formed.

[Jacques]

Some time ago I thought that the iron dust of the rings can accelerate the process. The proto star magnetic field magnetize this iron and create concertration of iron along the magnetic line. A dust colliding with an other dust must not count only on gravity to agregate. May be relative velocity are hight enought the two dust just fuse?

At that scale magnetism is a lot stronger than gravity. I guess in just a few millions years you grow body size from dust to boulder of iron. Not to long after that gravity will play a bigger role. Iron core are suspected at the center of earth and of other planets.

I would like to know if the planetary formation model took magnetic and electric forces in consideration?

Vladimir:

Nebulae are gaseous.

Our sun was form a supernovae remanent, enriched with metal (metal is atomic weigth>2). It is a second generation star. The supernovaes have iron lines in there spectrums. Iron is the end of the fusion process, no more fusion that giveup energy. Nothing to oppose gravity. If big enought it collapse and explode!

A first generation star is made from a cloud of H He and a little bit of Li.

[Vladimir]

Yes i think thats the point i made, that gravity does not play a signifficant role until the latter stages of development. The velocity of teh particles is presicely the point that i was trying t i make, and that planets do not rely on dense parts of rings.

Its still what i said though, nebulae are gaseous, and have prescious (if any) little part in the creation of a planet. After all what is a planet?

[coquina]

What you wrote about magnetism makes a lot of sense to me.

[swansont]

Some time ago I thought that the iron dust of the rings can accelerate the process. The proto star magnetic field magnetize this iron and create concertration of iron along the magnetic line. A dust colliding with an other dust must not count only on gravity to agregate. May be relative velocity are hight enought the two dust just fuse?

At that scale magnetism is a lot stronger than gravity. I guess in just a few millions years you grow body size from dust to boulder of iron. Not to long after that gravity will play a bigger role. Iron core are suspected at the center of earth and of other planets.

I would like to know if the planetary formation model took magnetic and electric forces in consideration?

Vladimir:

Our sun was form a supernovae remanent' date=' enriched with metal (metal is atomic weigth>2). It is a second generation star. The supernovaes have iron lines in there spectrums. Iron is the end of the fusion process, no more fusion that giveup energy. Nothing to oppose gravity. If big enought it collapse and explode!

A first generation star is made from a cloud of H He and a little bit of Li.[/quote']

 

Magentic forces may or may not be stronger, depending on what materials are involved, but they fall off faster with distance.

 

I think the sun is third generation; the result of a second-generation supernova.

[kotake]

As the solar system formed, the gravity of the sun drew in the heavier, more dense chunks of planetary dust - that is why the inner planets, Mercury, Venus, Earth, and Mars, are rocky. And the outer ones are composed of gas.

Interesting. This suggests that the likelihood of finding gas giants close to a star are remote at best.

Actually, during the latter years, there have been found over 100 other solar systems that have gas giants as inner planets. Thus the model works for our Solar System, but can not be generally applicable.

 

According to a new theory nebulae don't spontaneously collapse (among others, the gas particles have too high velocities when they collide to be able to stick together) - in order for particles to clump together and form planets they must be activated by enormous external forces. These forces may come from supernova explosions, which emit shock waves and destabilise the gas clusters. The gases then collapse and start hydrogen fusion, giving birth to stars. Remaining dust settles like disks around the new born stars.

When other supernovae explode they provide the systems with heavy elements, like iron. The elements intermingle with the gas disks, and thus planets form, orbiting the star.

[KholdStunner]

-getting back to the original question-

 

a new theory called 'intelligent design' would have an easy answer to this, which would be: an intelligence made the particles move together, because it has a certain purpose in the universe (kind of like 'divine-plan' theory)

 

-anyways, i suppose its just randomness. There are probably trillions of chances that particles could move togetehr and stick, and eventually form a planet, but only a few actually do so.