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cuboctahedron
2004-Apr-13, 04:34 PM
Sorry for my ignorance perhaps...

Why do all the planets in our solarsystem orbit the sun in the same '2-dimensional layer' if I can call it that.
If you look at a classical map of our solarsystem, you can see all planets circling around the sun (for sake of argument, in a X- and Y axes environment), but all appear to be aligned on the Z axe, moreorless.


Patrick

ToSeek
2004-Apr-13, 04:52 PM
The solar system formed from a collapsing and increasingly rotating mass of material. As it gathered together and started spinning faster, it naturally formed less of a sphere and more of a disk. When the planets formed, they did so on the disk.

George
2004-Apr-13, 04:59 PM
It is believed that an accretion disk develops from a "cloud" during the formation process of stellar/planetary systems. Planets develop from this disk which lies in the x-y plane as you described.

Apparently, the dynamics are extensive and computer modeling is probably very heavy duty. There is only limited detail observation but they do exist thanks to the Hubble Space Telescope for one. Future scopes will provide even better information, of course.

There is probably much more on this board regarding this and you can "search" if you desire.

Normandy6644
2004-Apr-13, 05:07 PM
IIRC, Pluto is the only planet to orbit with a really high inclination, whereas the other planets do lie in more or less the same plane. A lot of this has to do with gravitational effects, but more likely (as George and ToSeek said) it's because of the way the solar system actually formed.

George
2004-Apr-13, 06:02 PM
The solar system formed from a collapsing and increasingly rotating mass of material. As it gathered together and started spinning faster, it naturally formed less of a sphere and more of a disk. When the planets formed, they did so on the disk.

Dang...you even type faster than me as your post beat mine. :)

[I will concede that you are humanoid and not Ultra A.I., but I am starting to wonder about your parents. :wink: ]

Ut
2004-Apr-13, 06:06 PM
Because I'm hungry, let me throw out an analogy. Take a ball of pizza dough and spin it. It flattens out, right? Same sort of deal with the solar system. Mind you, the dynamics of a solar nebula are far more complex than those of tasty, tasty pizza dough.

Now, to get out of here before Sam5 protests that the planets are not made of bread products...

George
2004-Apr-13, 06:15 PM
Since we're on the subject....

One of my "wish I could find out for sure" projects is to determine if conditions of the pre-planetary disk would appear colorful to a visitor nearby. As I recall, some models show significant densities within the disk. Rayleigh Scattering might become effective at creating a blue disk, but this is speculative at best, at this point.

Squink
2004-Apr-13, 06:37 PM
If the orbits of two planets are not coplanar, then any gravitational interaction between the two planets will exert a force that is out of the planes. That force will change the planes of the planet's orbits, and that'll keep happening until the planets end up either too far away from each other for significant gravitaional interaction, or they end up orbiting in the same plane.

Ricimer
2004-Apr-13, 06:54 PM
and that interaction is very easy to achieve with a gas (which is why the disk forms) than with large, concentrated masses (planets) which have lots of collective inertia.

I.e. it happens much, much faster with gasses than with planets.

George
2004-Apr-13, 10:29 PM
Is it reasonably known the make-up of the particulate matter of the accretion disk? I suppose initially, it is primarily hydrogen and helium until the stellar winds fire-up.

Is it likely the planets are fairly well established in mass prior to nuclear ignition?

Any good links out there?

Brady Yoon
2004-Apr-14, 01:16 AM
Is it reasonably known the make-up of the particulate matter of the accretion disk?

It was mainly hydrogen and helium, but there was also a little bit of heavier elements created by earlier generation stars. We are living proof of that!



Is it likely the planets are fairly well established in mass prior to nuclear ignition?

Most likely yes. The T-Tauri stage when the sun was a protostar cleared out most of the solar nebula from the solar system before nuclear ignition took place.

milli360
2004-Apr-14, 01:28 AM
If the orbits of two planets are not coplanar, then any gravitational interaction between the two planets will exert a force that is out of the planes. That force will change the planes of the planet's orbits, and that'll keep happening until the planets end up either too far away from each other for significant gravitaional interaction, or they end up orbiting in the same plane.
Except, there is the example of globular clusters.

Squink
2004-Apr-14, 01:46 AM
Except, there is the example of globular clusters. Merely a transient phenomena. Give them 1076 years or so and they'll settle down to a more reasonable shape. :wink:

Ricimer
2004-Apr-14, 02:24 AM
Globular clusters are good examples of massive objects (i.e. stars) don't settle out nearly as fast as gas and dust does.

Globular clusters are ancient, home of the first stars to form in the region (as is our galactic core, which is basically an uber-huge globular cluster). These stars formed rapidly, and once ammased into huge masses (stars) they had so much collective inertia that they haven't really settled out much at all, 13 billion years later.

The gas and dust that swirled around the big globular cluster (our galactic bulge) quickly settled out into a disk before much of it formed stars (heck, most of it is still gas and dust).

George
2004-Apr-15, 12:07 AM
Is it reasonably known the make-up of the particulate matter of the accretion disk?

It was mainly hydrogen and helium, but there was also a little bit of heavier elements created by earlier generation stars. We are living proof of that!

Thanks Brady. It spurred me to take a closer look.

This is interesting...


What are Giant Molecular Clouds composed
of?
The interstellar medium is roughly 99% gas, 1% dust by mass
Of the gas, roughly 90% is hydrogen (H2 and H), and 10% is helium,
with some CNO-based gases (i.e. hydrocarbons)
Ice grains composed of CN0-based molecules (mainly water, ammonia, CO, etc.)
Dirty sub-micron-sized grains of magnesium and iron silicates

From.... GMC's (http://etacha.as.arizona.edu/~eem/ttau/gmc.html)