1)At what angle is the plane of the solar system inclined, if it is, to the galactic plane? 2) If it is inclined, when it revolves around the center of the galaxy, does it hold to a single orientation (as the earth does as it revolves around the sun), or does it not? For instance say it is inclined at 90 degrees would,say the north pole of earth always point toward (or away or whatever) the center of the galaxy, or not? 3) If the solar system’s plane is inclined at 90 degrees or something close, which way does the north pole point: toward or away from galactic center? 4) At what angle are the planes of the galaxy and that of the Andromeda Galaxy inclined, one to the other? 5) Do the stars of the galaxy have any motions other than moving in fixed positions around the center of the galaxy? I guess I mean motions with respect to each other? 6)I have heard that our solar system rides up and down in undulation as it also moves around the center of the galaxy. Is this true, or merely a rumor?
You’re new here, so you must not realize there is another forum for posts like this: “General Questions.” I bet it gets moved there by tomorrow.
And I wish I knew enough about astronomy to answer your questions! :o
My first response would be - is our solar system on a plane? I didn’t realize all the planets were on the same z axis. What a waste of 3 dimensional space.
1-4) I’ll have to check on the angle of inclination stuff.
5) Yes, the stars have motion other than in neat ellipses around the galactic center. There is some local interactions and there are the density waves of the galaxy’s spiral arms that move things around too.
6) Yes, it’s true that our solar system oscillates up&down through the galactic plane in addition to its revolution around the galactic center. At the moment I forget the frequency, but I can probably find out for you (something on the order of millions of years). Since the galactic plane is more crowded (nebulae, etc.), some people speculate that the solar system’s passage through the galactic plane triggers all kinds of havoc (e.g., mass extinctions resulting from comet impacts, reduced sunlight reaching us, etc.)
The orbits of the planets & asteroids are all very close to the same plane (Pluto is the biggest freak at a 17 degree offset, IIRC). This is due to the way the solar system formed (nebula that flattened to a disk of material as it collapsed). However, the Oort Cloud (home of the long-period comets) is theorized to extend in all directions.
This is much more a General Questions topic, don, but I’ll give it a shot.
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The galactic center is located at 94.5W longitude, 28.9S latitude in equatorial coordinates. That is, it is about 30 degrees south of the celestial equator and about 95 degrees west of the vernal equinox. Does that clear it up? Essentially that means the solar system’s equatorial plane and the galaxy’s equatorial plane are inclined 30 degrees to one another.
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In the absence of other effects, yes, it maintains its orientation, but a lot of other effects can occur in the time it takes to orbit the galaxy. The north pole of the earth would point toward or away from the galactic center depending on its position in orbit. (Actually, I assume you’re really concerned about the north pole of the solar system, not the earth. It, too maintains it’s orientation – on one side of the galaxy it will point more or less toward the center, on the other side of the galaxy it would point away.) The earth, of course, points toward or away from the galactic center depending on its orbit around the sun – half the year it points toward, half it points away.
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The solar system’s north pole points away from the galactic center.
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I dunno. My reference is limited to the solar system.
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Yes they do. Astronomers measure the “proper motion” of stars relative to the “fixed” background. It’s hard to measure for stars that are far away because the angular motion is so small, but for nearby stars it can be calculated.
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Where do you get your rumors from? There may be undulations due to gravitational effects or from waves of pressure sweeping through the galaxy, but I don’t know if these are detectable or not. Again, in the absence of any other effects, the orbit would remain planar.
…still looking for references on the angles (& a reference for question 6 since pluto & I had different answers), but here’s a good link for our solar system itself
Did anyone else notice the irony that Pluto and Phobos are among the few to reply to this thread?
Hey, if you know something (re: #6), Phobie, share it. I was only going on the general principle that conservation of momentum would restrict the orbit to a plane in the absence of external forces. As I said (I hope) I don’t know whether or not there are external forces.
Quoth pluto: “Essentially that means the solar system’s equatorial plane and the galaxy’s equatorial plane are inclined 30 degrees to one another.”
Eh… I dunno. Are you sure about this? Correct me if I’m wrong, but the angle we’re looking for is the same as the angle between the Milky Way line and the Ecliptic. Looking at my sorry little starmap, I’d say that looks more like 70° than 30°.
Does it make sense, other than tradition, to define the solar system with reference to the plane of the Earth’s orbit? Wouldn’t either the plane of the Sun’s equator, or Jupiter’s orbit, be much more significant gravitationally?
It’s mostly tradition, but converting the measurments to another plane would increase the number of calculations that have to be done. At any rate, the difference between these planes is only 1 or 2 degrees, I believe.
As far as the angle between the ecliptic and the Milky Way, it’s about 60[sup]o[/sup]. From what I understand, the plane of the solar system precesses over the course of its orbit around the galaxy, so the north ecliptic pole will move around. However, the angle should stay about the same.
I am willing to concede that I misinterpreted the -28.9 degrees number that I quoted. It’s entirely possible that it was the co-latitude, in which case the angle would be about 60 degrees, in line with the other reports here.
Offhand, I would think that the best reference would be the equator of the sun. But the orbital planes of the first 8 planets are very similar.
I had the same question.
I think our names are a giveaway! 
Astronomy rules! I’ll definitely keep looking for a reference on #6. I think I heard it from Carl Sagan (Cosmos? Pale Blue Dot?).
Quoth pluto:
I’m sure that you saw the mistake, pluto, and just didn’t want to admit it. Barring very long-term (much more than a year) effects like precession, the north pole of the Earth always points in the same direction (approximately toward Polaris), which is more away from the center than towards it. If the orientation of the Earth were to stay the same over half of an orbit of the Sun about the center, then the center would be to the Earth’s north.
As to the oscillations, the orbit of the Sun, if unperterbed, would indeed be a plane, but that plane does not necessarily correspond to the plane of the rest of the disk. If it does not, then the effect would be that the Sun would move “above” and “below” the plane, in the same period as its orbital period. Is this what you mean by “wobbling”?
Finally, on the ecliptic: The best definition would probably be based on the net angular momentum of the Solar System, which is dominated by the orbital movement of Jupiter. Since all of the planets that aren’t also Kuiper belt objects (no offense to anyone else in this thread 
) are withing a degree or two of the same plane, it’s not much different than using the plane of the Earth.
Hey, a few related questions for you…
I of course realize the planet’s trajectories are primarily controlled by the Sun’s gravitation, but it seems the planets’ gravitational interaction with each other would have some significant effect on the z-axis of the solar system. In fact, wouldn’t it be the most significant variable component of the planet’s delta-z motion, other than possibly the occasional collision?
I would think that after enough time, the planetary planes would tend to oscillate around due to this planentary interaction until they were all nearly equal, as they are now. Have there been any computer models on this? Can we run these interactions in reverse to see how the planets were oriented X years ago, or is it thought the chaotic interactions would render such simulations far too inaccurate? Have there ever been any observable changes in planetary planes over the last few hundred years, keeping in mind such changes would obviously be minute degrees of an angle?
Pluto wrote:
I think this is true if you mean a galactic year rather than a standard year. The precession Chronos mentions would be a factor, but from a galactic year perspective it would be a short-term effect, I think. You may have intended this, but the context didn’t make it clear. It is a factor of about 200 million, if I recall my Monty Python lyrics correctly.
Mrblue92:
If the planets are all nearly in an xy plane, they wouldn’t exert much force out of that plane on the z direction. Not until they were perturbed from the plane would they exert force in the z direction. I don’t see a reason why the other planets would dampen an out-of plane motion, in fact I would expect the opposite. The explanation I’ve always heard for the planarity was in the angular momentum of the accretion disk during the formation of the solar system. The planets (except Pluto) were thus formed in a plane and haven’t deviated much from it since.
Yes, I know, but we’re talking LARGE periods of time here.
Yes, I’ve heard this too, but it seems like a pretty big assumption to me–I would think it’s something one might want to do a computer simulation of.
Galactic Plane
Phobos
You are right about the solar system oscillation around the galactic plane. This motion is proposed to cause an increase in the cometary flux into the inner solar system due to the gravitational effects generated by the Giant Molecular Clouds–GMCs-- which the sun encounters when it races past the densely populated plane of the galaxy.
I am not totally sure, but I believe the oscillation period would be around 50 million years, since then the passage by the galactic plane would match the purported 26 to 30 million year range that cataclysmic extinctions on earth follow.
Duncan Steel mentions this point in his book Rogue asteroids and doomsday comets which I highly recommend.
Maybe a web search of the nemesis hypothesis, which is a related subject, might produce relevant results that will support the above cited information.
*Originally posted by Chronos *
Ya know, it’s not so much that I don’t want to admit it, it’s just that it happens so often it’s kinda boring.
Let’s see. I was wrong on the angle. I was wrong on the pointing. I still don’t think I was wrong on the oscillations but a lot of you seem to disagree.
I have a new theory. There’s this huge turtle, see, and he carries the galaxy around on his back. Well, not directly on his back. The elephant is standing on the turtle and the galaxy is on the elephant’s back. And so on.
Nope. The Earth’s crust is the back of a turtle, it is standing on the back of a somewhat larger turtle, and it’s “turtles all the way down”. It is widely accepted there are no elephants.
Hah! …the astrochelonian moves!