Solar system plane question

[dogjones]

Every representation of the solar system I know represents the planets revolving around the sun, all pretty much on the same horizontal plane, like rings of Saturn.

Is this actually the case in reality? If so, why are there no planets revolving around the sun on the vertical plane? And how about comets – are they roughly on the same plane as well? Again, if so, why none on the vertical? Does gravity/inertia etc tend to even orbital systems out onto one plane?

 

[Lothian]

Every representation of the solar system I know represents the planets revolving around the sun, all pretty much on the same horizontal plane, like rings of Saturn.

Is this actually the case in reality? If so, why are there no planets revolving around the sun on the vertical plane? And how about comets – are they roughly on the same plane as well? Again, if so, why none on the vertical? Does gravity/inertia etc tend to even orbital systems out onto one plane?

There are pretty much on the same plane. They differ by the following degrees from that of earth.


Mercury 7
Venus 3.394
Earth 0.000
Mars 1.850
Jupiter 1.308
Saturn 2.488
Uranus 0.774
Neptune 1.774
Pluto 17.15


Why ? I don't know.

 

[Terry]

There are pretty much on the same plane. They differ by the following degrees from that of earth.


[...]


Why ? I don't know.

Because they condensed from a disc of material around the newly-forming sun. A rotating cloud will tend to collapse into a disc.

Long period comets aren't confined to the plane of the ecliptic, if I recall right.

 

[Loss Leader]

You can do this experiment yourself with pizza dough. After the dough has risen, it will look something like a sphere. Throw it into the air with a twist. As it rotates, it will flatten into a disk. The more you do it, the flatter it will get.

And that's how a caterpiller turns into a moth.

 

[dogjones]

OK, so if the comets didn't form from the original cloud around the newly-formed sun, where did they originate from? Could they have formed on the edge of another disc somewhere else and then 'catapulted' towards us?

 

[sol invictus]

The same holds for our galaxy - it's a pretty flat disk apart from a bit of a bulge in the middle. In fact that's true for most other galaxies as well - the exceptions (elliptical galaxies, for example) generally formed from the merging of two disk galaxies.

Take a look at this, for instance.

The reason is more or less as others have said - angular momentum is hard to get rid of, but energy can be reduced in various ways. If you start with a rotating cloud and reduce its energy while keeping its angular momentum fixed, it has to flatten into a disk.

 

[Damien Evans]

OK, so if the comets didn't form from the original cloud around the newly-formed sun, where did they originate from? Could they have formed on the edge of another disc somewhere else and then 'catapulted' towards us?

No, they're leftovers, so to speak, from the original cloud. Many are in the same rough plane as the planets, but many of the ones from further out are not, presumably because they were already formed before the cloud collapsed into a disk, or perhaps were shunted there later. I am not an Astronomer.

 

[wollery]

The same holds for our galaxy - it's a pretty flat disk apart from a bit of a bulge in the middle.

Well, not exactly. It consists of 4 principal components, the halo (which is roughly spherical, although the exact shape is a subject of much debate), the thick disk, the thin disk, and the bulge. The reason it's hard to see the halo is that it's a lot older than the 2 disk components or the bulge, and all of the big bright stars have burned out, leaving just the small faint red ones. The halo also contains some stars from old stellar clusters, satellite galaxies of the Milky Way that were torn apart by its gravity.

 

[Dancing David]

OK, so if the comets didn't form from the original cloud around the newly-formed sun, where did they originate from? Could they have formed on the edge of another disc somewhere else and then 'catapulted' towards us?

that is a huge area of study at this time!

Look up Kupier belt and Ooort cloud and then ,Centaur objects, plutoids and planetesimals.

 

[sol invictus]

Well, not exactly. It consists of 4 principal components, the halo (which is roughly spherical, although the exact shape is a subject of much debate), the thick disk, the thin disk, and the bulge. The reason it's hard to see the halo is that it's a lot older than the 2 disk components or the bulge, and all of the big bright stars have burned out, leaving just the small faint red ones. The halo also contains some stars from old stellar clusters, satellite galaxies of the Milky Way that were torn apart by its gravity.

The reason it's hard to see the halo is that it's mostly (by a large factor) dark matter, not that it's mostly burned out stars.

But anyway, that just adds detail to what I was saying - those old stars formed in the early stages before the disk had flattened, and they stay in spherical orbits because they interact very little and can't dissipate much energy (unlike the gas that flattened into the disk and later formed stars). Same goes for dark matter - it evidently has very weak interactions.

 

[GreyICE]

The reason it's hard to see the halo is that it's mostly (by a large factor) dark matter, not that it's mostly burned out stars.

Is this exotic dark matter, or the conventional stuff? I'm just curious.

 

[DavidS]

There are pretty much on the same plane. They differ by the following degrees from that of earth.

<snip>

Why ? I don't know.

[disclaimer] I am also not an astronomer. I'm merely an engineer, and one for whom rotational mechanics never quite 'clicked'. Still, I offer the following elaboration of Terry's explanation.[/disclaimer]

Consider that the particles of the primeval nebula were moving in more-or-less random directions. Since almost none of those trajectories were in line with the center-to-be, all those particles had some angular momentum about that center; some up, some down, some sideways, some tilted. Since angular momentum is conserved, when those particles lump together the star planets carry the sum of the original particles' momenta.

That sum isn't quite zero, so the big chunks end up spinning around an axis. Particles (or dough) toward the "north" end of the axis feel more gravity (or tensile force) pulling them "south", and vice-versa; this flattens the system (or pizza) into more of a disk (pie) shape.

Smallish chunks from the "ends", though gravitationally bound to rotate more-or-less about the axis, might make many highly tilted or eccentric passes through the "disk" before they hit and stick to something big enough to swallow their momentum and confine them to orbit more circularly about the plane with their bigger brethren. Methinks most comets are such chunks.

 

[sol invictus]

Is this exotic dark matter, or the conventional stuff? I'm just curious.

We don't know what it is - just that there's a lot of it. Microlensing surveys have more or less ruled out the possibility that all or most of it is in chunks the size of stars. Combined with evidence from the rest of the observable universe we can constrain a number of it's other properties. But we still don't know what it is, or even if it's truly "exotic".

The most exciting new development in that area are the PAMELA results - that's a satellite looking at high-energy positrons, and there's a strong hint it's detected something that would be explained pretty well as dark matter annihilation. See here for example.

 

[dogjones]

[disclaimer] I am also not an astronomer. I'm merely an engineer, and one for whom rotational mechanics never quite 'clicked'. Still, I offer the following elaboration of Terry's explanation.[/disclaimer]

Consider that the particles of the primeval nebula were moving in more-or-less random directions. Since almost none of those trajectories were in line with the center-to-be, all those particles had some angular momentum about that center; some up, some down, some sideways, some tilted. Since angular momentum is conserved, when those particles lump together the star planets carry the sum of the original particles' momenta.

That sum isn't quite zero, so the big chunks end up spinning around an axis. Particles (or dough) toward the "north" end of the axis feel more gravity (or tensile force) pulling them "south", and vice-versa; this flattens the system (or pizza) into more of a disk (pie) shape.

Smallish chunks from the "ends", though gravitationally bound to rotate more-or-less about the axis, might make many highly tilted or eccentric passes through the "disk" before they hit and stick to something big enough to swallow their momentum and confine them to orbit more circularly about the plane with their bigger brethren. Methinks most comets are such chunks.

Cool, I was just about to ask, sticking to the pizza dough analogy, "what got the system rotating in the first place" - I think you have just offered an explanation for this. Although I find it very difficult to get my head around how angular momentum works.

 

[Loss Leader]

I am not an Astronomer.

Neither am I. I'm a lawyer. But I came up with the pizza dough thing all by myself. It took me an hour.

 

[TMiguel]

I have been recently given a talk about satellites on this matter. Because of the principle of distribution of energy (bla bla and all that), the system tends to rotate more or less in the same direction.
Now here is the funny part, because of something called centrifugal acceleration versus the gravity acceleration, everything whit orbits not quite in the horizontal plane tend to slip away, while the rest that doesn’t slip away most likely collide whit something else and disappear over time. They don’t need to be exactly in one plane, but it is really a very broad volumetric band (although relatively not that much wide).

 

[wollery]

The reason it's hard to see the halo is that it's mostly (by a large factor) dark matter, not that it's mostly burned out stars.

I was only referring to the stellar halo, and the burn out of the more massive stars is a large factor in why we don't see that, but yeah, the dark matter halo is also roughly spherical.

But anyway, that just adds detail to what I was saying - those old stars formed in the early stages before the disk had flattened, and they stay in spherical orbits because they interact very little and can't dissipate much energy (unlike the gas that flattened into the disk and later formed stars). Same goes for dark matter - it evidently has very weak interactions.

Exactly.

 

[portlandatheist]

Isn't this process ongoing to this day via the attraction the planets have to each other? It seems for example that every time we pass nearest Jupiter's pull it would bring us more and more in line with the same orbital plane as Jupiter and the rest of the planets likewise.

 

[TMiguel]

Isn't this process ongoing to this day via the attraction the planets have to each other? It seems for example that every time we pass nearest Jupiter's pull it would bring us more and more in line with the same orbital plane as Jupiter and the rest of the planets likewise.

The planets orbits are more chaotic then most of the people originally think.

 

[Undesired Walrus]

You can do this experiment yourself with pizza dough. After the dough has risen, it will look something like a sphere. Throw it into the air with a twist. As it rotates, it will flatten into a disk. The more you do it, the flatter it will get.

And that's how a caterpiller turns into a moth.

Why isn't the Earth flat then?