Astronomy/cosmology questions...

[Buster's Uncle]

SO - I just saw some NASA Kepler thing from May that was explaining occultation detection at the outset, and I wanted to ask about something I've wondered for quite a while; it's obvious that the technique has the severe limitation of only being any good when the system's plane of ecliptic -or at least the orbit of any given individual planet there- lines up in the same direction we're looking from in at least one dimension - of course.

Casual observation tends to confirm that earth's rotation is somewhat lined up with the galaxy's plane, the Milky Way being not terribly far off the equator in our sky and our rotation being roughly in the same plane as the solar system's ecliptic.  1.) How common does that seem to be in other systems, the ecliptic being sorta lined up with the rest of the galaxy, noting plenty of exceptions in our own solar system (most obviously that the moon so rarely lines up exactly with the sun relative to any particular terrestrial POV, but also thinking of Neptune and Pluto), both in orbit and rotation?  And 2.) given the local group of stars being not on a flat plane at all in relation to each other -I believe Wolf 359, for an example of a dinky close star only famous for a fake Star Track Borg battle, is considerably to our galactic north, as Alpha Centauri is south to the extent it's never in our sky in the rightside-up proper American part of the globe- how frequently is occultation detection useful on a relatively local scale?  -It seems intuitive that a north-south deviation from our viewing angle becomes less significant the further away the star being observed is, though of course resolving the light dip becomes more difficult with distance and relative dimness and balances out at some relative limit...

[Lorizael]

So, there's an angle of about 60 degrees between the galactic plane and the plane of the ecliptic, which means we're not really all that well lined up with it. Wonky configurations relative to the galactic plane seem to be pretty normal, which we know because we basically see planets as often as we should. That is, if extrasolar ecliptics are distributed randomly, then only a small percentage of stars should be in line with us, and observation says we don't see more than that percentage with planets.

The real limitation is that it's much less efficient to look up or down or out, because we are basically situated two thirds of the way out from a very flat disk.

[Buster's Uncle]

Okay, thanks.  That's pretty much what I wanted to know about that part.  Go on...

[Lorizael]

What else would you like to know?

Also, I want to make sure we're on the same page. You mentioned occultation throughout, but if you're talking about detecting planets, astronomers tend to refer to that as the transit method. Occultation is usually mentioned in the context of a foreground object (something in the solar system) passing in front of a distant star. In that case, of course, planes don't really matter. Occultation can be used to discover objects in the solar system (asteroids and comets, for example) by directly blocking the light of another star or to learn about solar system objects we already know are there. For example, we can find the chemical composition of, say, a moon's atmosphere by seeing which wavelengths of light from an occulting star it blocks.

[Buster's Uncle]

Okay; I'm not disinterested in getting the slightly jargony bit right.  I'm interested in your reactions to anything I say on the subject, as your formal training is educational to me on a subject I find interesting, for all that I've never studied it seriously, just picked up in passing as much as any science fiction geek with a mind who reads should.

It seems increasingly plain, as our scant knowledge of our own solar system becomes slightly less pathetic, something that should have been more intuitive; very very faint gravitational influences really add up, given billions of years, thus things like orbital resonances being far more common than the pros seemed to assume when I was a kid - and of course, that's pretty much how we get prevailing planes of ecliptic, there being evidence that early system formation is a more than trivially chaotic event...  -Not that they didn't suspect a good deal of that as far back as Newton, but still found many a surprise around Saturn in 1980, observation always proving higher-rez than theory...  I'd opine that it wasn't the Newtonian/Einsteinian laws that were insufficiently worked out IRT space -I'm sure there's plenty the state of the art doesn't grok, but they seem to be at least a not-inadequate working approximation for many purposes- but the implications of timescales we're frankly incapable of intuiting.

-But then oort clouds must be too distant, and of insufficient average mass, for all that to work on our system's timescale of existence - certainly, any tendency for star systems lining up planes in a galaxy the age of ours would be almost solely due to any prevailing tendency of movement direction of galactic matter clouds at formation; if Pluto and the comets haven't lined up yet, in other words, an Alpha Centauri system needs a timescale difficult to even guess at by an order of magnitude or three.

Related in my mind, on the subject of deep time; when I came to understand how they thought bits of Mars could end up laying in Antarctica -no news story EVER, to my knowledge, said "meteor splash" for about ten years- I began to believe in the possibility of a sort of panspermia for the first time, w/o invoking Sargon's people (ST reference).  Given enough spores and time and a few energetic events, there's just no telling how far a single origin of life could spread, at least on an intra-galactic scale.

[Lorizael]

One thing I'll mention is that solar systems being basically planar is primarily a result of the conservation of angular momentum, not gravitational influences. Here's a good way to think about this. Before the solar system formed, you had a molecular cloud sitting around, waiting to collapse under its own gravity (which would happen if it were perturbed by a supernova or a passing star, say). All of the particles in this cloud are basically moving around randomly, but you can think about their direction of movement relative to the center (where the star will be). If you then add up all of those random directions of movement, you'll find that the sum of those movements points in one particular direction. (This isn't special; it's just math. Add up a bunch of numbers and you get one number. Add up a bunch of directions and you get one direction.)

Once the cloud starts collapsing under its own gravity, conservation of angular momentum means the particles will all start spinning faster. They're still all moving randomly, but their average spin direction is the summed up direction from earlier. As the cloud collapses, more and more particles start running into each other, which tends to cancel out the random motions of the particles in the cloud. If all the random motions cancel out, you're left only with the average motion in one direction, which is some spinning orientation around the center where the star is. So you're left with a flat disc.

The reason something like the Oort Cloud isn't planar is either because (a) it wasn't really part of the initial collapse of the molecular cloud or (b) it consists of bodies that were chaotically thrown out of the solar system early on during formation.

As far as orbital resonances are concerned, there are two interesting discoveries that have been made as astronomy has matured. One is that resonances sometimes create gaps, but only on very long timescales. So, for example, there are gaps in the asteroid belt (the Kirkwood gaps) corresponding to resonances with Jupiter. Gravitational tugs over time mean that any asteroids at those distances get kicked out, but only over very long periods of time. So billions of years after Jupiter has settled into its current orbit, basically nothing remains there, but long ago there would have been asteroids present in unstable orbits.

The flip side of this is that some objects in resonances we currently see only exist because the configuration at present is relatively young, and eventually those bodies will get kicked out. That we see orbital resonances at all in the solar system actually suggests that the current orbits of planets and moons might be relatively recent (still speaking of tens or hundreds of millions of years). Astronomers are pretty confident that Jupiter and Saturn did a fair amount of migration early on, for example. But additionally, something like Saturn and its rings may be quite young, fragile, and short-lived on a solar system timescale.

[Buster's Uncle]

First half -not that I could have phrased it as well- pretty QED.

Second, largely just best informed assumptions available.  I've been watching the science of the nature and age and orbital mechanics of Saturn's rings, for instance, go back and forth longer than you've been alive.  Forgive my doubt until our observations are less pathetically incomplete...

[Lorizael]

I think there are legitimate reasons to be less skeptical of recent results in the study of the solar system. Over the course of your life, we've learned a tremendous amount about the planets and moons from probes and telescopes, and we've also seen significant advances in chaos theory, a mathematical tool for studying dynamical systems (such as the solar system).

Additionally, the people I've learned this stuff from are just as old as you, if not older.

[Buster's Uncle]

-And actually know what they're talking about, sure.

I still wish our observations were a lot closer to complete/satisfatory.  Thomas is my favorite disciple.

[Lorizael]

It'll be awhile. Consider how much we don't know about the Earth, and then remember that the Earth is a dot as far as the solar system is concerned. We are definitely learning, but there is just so, so much to know.

[Buster's Uncle]

I wish there was more will to learn it...

[Buster's Uncle]

Oh - and only slightly related -because everything is- but check the LHC story topped in general science if it's not old news to you about the new particles...

[Valka]

Lorizael, I've got a question related to the asteroid belt. There's a guy on CFC who is obsessed with convincing us that Babylonian mythology and Genesis are accurate descriptions of how the solar system and Earth were formed. He keeps insisting that Earth was formed in the asteroid belt because our water and Vesta's water are identical.

I can't find anything online anywhere that states even the possibility of Earth forming in the asteroid belt. Do you know of any theory or even a hypothesis by a reputable astronomer that talks about this?

[Buster's Uncle]

I believe I know what he's trying to talk about, but Lori will explain it a lot better and more accurately than I.

Protip: think oceans from comet water instead of Earth forming in the belt.

[Valka]

I believe I know what he's trying to talk about, but Lori will explain it a lot better and more accurately than I.

Protip: think oceans from comet water instead of Earth forming in the belt.

That's pretty much how I figured it, but he's absolutely not willing to listen to any views but his own, even those of real astronomers and astrophysicists.

I was willing to concede that I may have missed some hypothesis or theory about this, so thought I'd grab the opportunity here to ask someone who is into real science, not tabloid/mystical nonsense.