In grade school in the ‘60s, I knew every (at the time) fact about the solar system. I am sorely embarrassed that this question just occurred to me 6 hours ago: is there a reason for the planets’ positions in the plane of our SS (why small-small-small-small-BIG-BIG-Mid-Mid-tiny heading out? Why not t-s-s-s-s-M-M-B-B? Or the converse?)? The real embarrassment is the phrasing of this question. I offer apologies.
I was thinking this the other day…
What if…
The Sun spits out hot planets out of solar plasma and they move away as they orbit [Mercury], then grow [Venus] then cool [Earth] then cool more [Mars] then go onto the asteroid belt and get pummeled to bits, or make it through and attract particles and gasses in the area [Jupiter] then slowly dissipate as they cool more [Saturn][Uranus][Neptune] then by that time they shrink to planetoids like [Pluto] then become balls of ice [Kuiper Belt] hurled back into the Sun to become Planets again in the distant future.
Ok, maybe not…
There is no particular reason that we currently know of for the particular arrangement of planets in our solar system. So far the extra-solar planets that have been observed do not match the pattern of our solar system, though this is not a random sampling since many of the methods of identifying extrasolar planets rely on large or particularly large planets to provide sufficient perturbance or ecplising their parent star. There have been many suggestions that the radii of the orbits (which are not dependant upon planetary mass) are the result of some kind of resonance between the planets (which is true of for the Galilean moons of the Jovian system), but except for a resonance between Neptune and the minor planet of Pluto no resonances have been demonstrated.
The planets are all in the plane of the ecliptic (or very nearly so) because they are composed of matter in the accretion disk left over after Sol condensed, and their angular momentum is conserved. Where aberations exist they are likely due to impacts or coulings that have caused one body to be ejected from the solar system leaving the other with an out-of-plane component.
Stranger
I’m not up on the exact details of the most current theories of the formation of planets, but I’m pretty sure that the notion that the planets came from the sun has been shown to be unworkable.
My old astronomy prof said that any large mass of sun-stuff that might have been ejected or torn or pulled or otherwise spewed from the sun would simply disperse, rather than coalesce.
The opening scenes of the dinosaur sequence in Fantasia showed the “near impact” theory of the earth’s origin, where a star or other object whished past the sun at high speed and dragged off material. I believe this idea was discarded shortly after WWII.
Me again! You guys are suggesting a cosmic game of billiards, aren’t you? Sol captures Mercury, Venus, Earth and Mars and together they (plus Sol?) capture Jupiter and they all together capture Saturn. Then J & S capture U & N and U & N snare Pluto? Nifty! I gotta go lie down.
What’s most fun is that some of that is true! Remember Shoemaker-Levy? To some degree, the solar system is a big game of billiards!
However, it isn’t true to the degree that Velikovsky said it was. Jupiter didn’t burp Venus out, to engage in a complicated game of bumper cars with Earth and Mars.
That said…some of the orbits they’ve used to send artificial satellites to Saturn or to Mercury are really, really gnarly. They’ll whip past the Moon…several times…to accrue or to shed orbital velocity. Then they’ll slingshot off Mars or Venus, etc. The overall paths can look like Odysseus’ course from Troy to Ithaka…with side-trips to Phaeacia…or Hades! The trajectories look like Spirograph traces…on acid!
A likely explanation of small rocky planets close to the Sun and gas giants farther out is that the inner planets lost most (or all) of their atmospheres due to the higher temperatures and greater force of the solar wind in their region of the Solar System. But, as was pointed out above, other recently discovered systems do not seem to follow this rule.
As for the spacing of the planets, there does seem to be a pattern, but current thinking is that it’s likely unique to our system. We simply don’t know enough about exosystems to form a judgement.
Also, there isn’t really a continuum from “tiny planets” like Pluto and Eris, through “small planets” like Earth, through “big planets” like Jupiter. They’re really three different sorts of objects, and in some ways, the iceballs (tiny planets) and gasballs (big planets) are more like each other than either is like the rockballs.
I had heard some theories about why the planets in the solar system are arranged the way they are, but I haven’t really heard any since 1995, when the first extrasolar planets were discovered. It may well be random chance that arranged our planets the way they are. From the extrasolar planets we’ve seen, it looks like migration of planets within a solar system once they are formed has a much bigger role than we used to think it did.
It’s actually an interesting case study in the failures of the scientific method. Back before the first exoplanets were discovered, all of the solar-system formation models predicted that you’d almost always get a few rockballs close in, and then a few gasballs further out. Then, they started discovering exoplanets, and pretty soon, the vast majority of known planets were close-in gasballs. For years after that point, all of the models predicted that you should almost always get close-in gasballs, with the rockballs (if any) being further out, and systems like ours being vanishingly rare. Then Kepler launched, and started finding a multitude of systems which are, broadly speaking, sort of like ours, and so now the models are making new predictions. All of these models are supposed to be constructed from first principles, and nobody was deliberately tweaking them to match the (known to be badly limited) data, but it ended up happening anyway.
Has anyone done a “failure analysis” on that? Might help avoiding “stacking the deck” in other situations, pointing out what to avoid.
Maybe.
This site has a pretty good explanation of how the outer solar system formed. There is a running simulation which shows the migration of Neptune from inside Uranus’ orbit to the outside of Uranus orbit.
I also think that Jupiter was able to catch the majority of Hydrogen and Helium being closer towards the Sun than the other gas giants, but far enough away that the Solar Wind didn’t push that material past Jupiter like it did with the inner planets. Saturn got the second highest amount, and the other two got the leftovers.
There was a paper published a while ago, maybe a year, where they ran simulations, and found it easier to end up with a solar system like ours if they started with a fifth gas giant, which gets ejected during the planetary migrations. (I didn’t read that entire site, so maybe they mentioned it there.)
Ah…The 5th gas giant hypothesis by Nesvorny., I missed that one…it was submitted back in Sept. 2011. It seems to improve on the hypothesis from the first site.