Early Solar System

[Fallingstar1971]

I remember reading somewhere that Uranus and Neptune swapped places in the early solar system and caused a shower of comets to rain down on the inner solar system. Has anyone else seen or heard of this theory? Is it valid?

I also read that Jupiter is perturbing Mercury's orbit. I have to ask, why isn't Jupiter perturbing Earth, Mars, and Venus? I would think that Mercury's orbit would be harder to change because its so close to the Sun. The rest of the inner rocky worlds have more mass, but are closer to Jupiter. I would think it would be easier for Jupiter to influence these worlds because they are farther from the Sun.

The only think I can think of is resonances, but I do not understand completely how they work. I know its a mathematical ratio between two orbiting bodies, but I do not understand how these things can "store" up energy and cause these major moves in the solar system. How is this energy stored? And what triggers its release?

Star

 

[MeteorWayne]

Yes, the theory, while unproven, explains a lot. Do a search on the "Nice" theory, IIRC, there are a couple of good references that come up.

As far as resonances, don't forget, Jupiter is 75% of the mass of the solar system that's not the sun. So much so, that the sun orbits around the center of mass of the solar system, and when Jupiter, Saturn and Uranus are on the same side of the sun, the sun orbits around a point above it's surface!

Mercury's orbit is very eccentric, so it is 50% further from the sun at aphelion then at perihelion. So when Jupiter is "there" when it's at aphelion, the tug is even stronger on the planet. It changes Mercury's orbit a little. Over billions of years, it's enough to change the orbit as these individual tugs add up.

Of course for the other planets, although their orbits are more circular, they are closer to Jupiter, so the effect of Jupiter's gravity ripples throughout the solar system.

Hope that helps.
MW

 

[Fallingstar1971]

Thank you, it does....

Interesting though, If NICE were true, then would there not be more objects in the outer solar system with reasonences to Uranus? Or is it that with all the time that has passed that they have adjusted themselves to Neptune only?

I watched a flash presentation on this, and at the moment of change it was like the chaos in an air powered popcorn popper with stuff flying around everywhere.

So these reasonces build up over time? A nudge here, a poke there, and before you know it Venus is now the closest planet to the Sun? But now Venus could be effected by Mercury, Earth by Venus, Mars by Earth (Well, perhaps at the orbit of Mars, Jupiters influence would be enough for it to resist Earth), but wow. Mess up just one Cog and the whole solar system machine falls apart.

Thanks again MW. I will be pondering the consequences of NICE for a while I think

Star

 

[MeteorWayne]

I think if you could read the actual papers, the model explains the Kuiper Belt cutoff as part of the Uranus/Neptune swap/migration process. It's been a few years since I read it.

As far as the resonances, yep a nudge here and a push there and over time it adds up to real money

the real stabalizing influence is Jupiter, because it's so massive and is in a close to circular orbit. So far that seems to be a rarity in the stellar planetary systems we've discovered so far... but in a few years when there is more Kepler and Corot data we'll have a much more thorough inventory of the types of systems that are out there.

 

[Fallingstar1971]

That is very interesting, consider this........

You said that when Uranus, Jupiter and Saturn are on the same side of the Sun, the Sun orbits a point above its surface.

Something occurred to me as I read that. Let me explain.

One method currently used in exo-planet detection is the "wobble" method.

Keeping in mind how this works, now I have to wonder, The Sun would certainly wobble if it were orbiting a point outside itself. But the most detectable wobble from the greatest distance would occur when the outer planets are aligned.

Perhaps this is what we are seeing with some of these exo-planets. Perhaps not "Super Jupiters" but instead more than one planet acting on the parent star at the same time. Exo-planetary alignments.

I do have to say, however, that the wobble should be over a long period of time, due to the rarity of alignments, and at the rate some of these stars wobble their planets would have to be almost always aligned, and that seems unlikely. Still though, I bet that some of the longer period wobbles that are seen very well could be multi-planet systems experiencing alignments.

And one thought leads to another, that leads to another..........

Star

 

[Invalid]

Couldn't just a hot Jupiter that close to its star do it? Jupiter has more mass than Neptune + Uranus. Plus being so close to its star. Isn't that one of the reasons that they are so easy to detect?

Although that could work on system more like ours.

 

[MeteorWayne]

That is very interesting, consider this........

You said that when Uranus, Jupiter and Saturn are on the same side of the Sun, the Sun orbits a point above its surface.

Something occurred to me as I read that. Let me explain.

One method currently used in exo-planet detection is the "wobble" method.

Keeping in mind how this works, now I have to wonder, The Sun would certainly wobble if it were orbiting a point outside itself. But the most detectable wobble from the greatest distance would occur when the outer planets are aligned.

Perhaps this is what we are seeing with some of these exo-planets. Perhaps not "Super Jupiters" but instead more than one planet acting on the parent star at the same time. Exo-planetary alignments.

I do have to say, however, that the wobble should be over a long period of time, due to the rarity of alignments, and at the rate some of these stars wobble their planets would have to be almost always aligned, and that seems unlikely. Still though, I bet that some of the longer period wobbles that are seen very well could be multi-planet systems experiencing alignments.

And one thought leads to another, that leads to another..........

Star

Each planet causes it's own wobble. They are superimposed on each other in the velocity of the star toward or away from the observer.. By observing long enough you can figure out how many planets are causing the different wobbles. (using Fourier analysis...a search will help explain that, it's a way to discover different periods hidden in a waveform). That is how we know about most multiplanet stellar systems.

It's also why we haven't found many systems like ours yet. In order to separate the periods of the individual planets, you need multiple orbits from each one, but we've only been looking for (generously) 20 years...the periods of the earth is of course 1 year, but Jupiter is 12, Saturn 29, Uranus 84, and Neptune 164. So it would take several centuries of observations to tell that our system has 4 massive planets and one tiny piece of rubble in the habitable zone

Wayne

 

[EarthlingX]

www.universetoday.com : Neptune Acquitted on One Count of Harassment

Oct 5th, 2010

by Nancy Atkinson


Illustration of a primordial Kuiper Belt binary during a close approach with the planet Neptune, similar to the encounters studied by Parker and Kavelaars. Credit: University of Victoria

A very popular explanation for the dynamical evolution of our solar system is being challenged by a new model that takes the blame away from Neptune for knocking a collection of planetoids known as the Cold Classical Kuiper Belt out to their current, distant home. PhD student Alex Parker from the University of Victoria in British Columbia, Canada presented evidence showing that the large population of binary objects in the Kuiper Belt gives witness to a different series of events than the Nice Model – which says Neptune’s migrations were responsible for a sending KBO’s into chaotic orbits. “Kuiper binaries paint a different picture,” Parker said during a press briefing at the American Astronomical Society’s Division of Planetary Sciences meeting this week. “I should title my talk as ‘Neptune not guilty of harassment’ or perhaps more accurately, “Planet Neptune acquitted of one count of harassment.’”

The Nice Model holds that the objects in the scattered Kuiper Belt were placed in their current positions by interactions with Neptune’s migrating resonances. Originally, the Model says, the Kuiper belt was much denser and closer to the Sun, with an outer edge at approximately 30 AU. Its inner edge would have been just beyond the orbits of Uranus and Neptune, which were in turn far closer to the Sun when they formed. As Neptune migrated outward, it approached the objects in the proto-Kuiper belt, capturing some of them into resonances and sending others into chaotic orbits.

But the survey of the Kuiper Belt being done by Parker and his thesis supervisor Dr. J. J Kavelaars (Herzberg Institute of Astrophysics), which has been running for a decade, tells a different story. “Thirty per cent of Kuiper Belt Objects are binaries, some in very wide orbits around each other in a slow waltz, weakly bound to their partners,” Parker said. “These binaries should have been destroyed if the Kuiper Belt Objects were thrown out of solar system.”

Since binaries are extremely common in the Kuiper Belt, they are useful tools for astronomers, said Parker. “Pluto and Charon are the most famous of these binaries and since their orbits can be affected by their environment, we can use them to test what the interplanetary environment is like and what it was like in the past.”

...

Diagram illustrating the process that destroys binaries during close encounters. Credit: University of Victoria

...

Read the team’s paper:“Destruction of Binary Minor Planets During Neptune Scattering,” Alex H. Parker, JJ Kavelaars

...

 

[marsbug]

The idea that uranus and neptune formed much closer to the sun is very attractive to those trying to model the accretion of those two worlds. If they formed at or near to their current orbits they would have taken so long to grow that all the hydrogen and helium gas in the protoplanetary disk would have dissipated before they could absorb enough to account for what we see. Like two guys trapped at the far end of the buffet table where all there is to eat is nuts- they shouldn't have been able to get so fat on that diet.

The alternative theory, which I guess this work supports, is that they formed by a different mechanism to the two inner giants - known as gravitational instibility- which woud mean they got very big very fast. Trouble is they're calculated to get much bigger than they actally are- so something must have cut them back down to size. I wonder if that something would have left its own mark on the kuiper belt?