# The Solar System: Our Missing Gas Giant



## Brian G Turner (May 27, 2017)

So I happened to stumble on a page at Wikipedia about a planetary formation model known as the Nice Model.

Simply put: no computer model of the formation of the solar system has can account for the positions of the planets as we see them today.

In other words, the solar system we see now cannot be the one that originally formed.

One theory that apparently comes very close is called the Nice Model. More specifically, the Five Planet Nice Model:

Five-planet Nice model - Wikipedia

What is extraordinary about this model are two distinct pointers:

1. The model accurately predicts a great number of the features of the solar system we see today, BUT

2. It requires the presence of a fifth gas giant, which is ejected from our solar system sometime before 3.5 billion years ago.


I'm not sure how accepted this theory is, or how accurate my interpretation of it from the Wikipedia page is.

However, I figure this might an interesting point of note or research for fellow chronners.

Not least the idea that we haven't just lost a planet, but a huge one at that.

Additional point: although predicted to have been ejected from our solar system, there remains a very slim possibility that is remains in our system as the Planet X currently being searched for - though consensus so far suggests that if Planet X exists, it was captured from a different solar system altogether. Which would mean we lost one but gained another ...


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## AstroZon (May 31, 2017)

Wow, that Wiki article is a bit thick (an animation would be quite useful.)  I'll have to read it again, but I think you have the gist of it.   

_"In January 2016, Batygin and Brown proposed that a distant massive ninth planet is responsible for the alignment of the perihelia of several trans-Neptunian objects with semi-major axes greater than 250 AU."_

I don't see why a gas giant couldn't have been ejected from our solar system.  It not only makes sense to me, but sounds a bit like a scifi short story I started a while back.


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## Alexa (May 31, 2017)

There are some reserches done to prove the existance of Planet X or Planet 9. I'm not sure I can believe that a planet could be ejected from our solar system.

'Planet Nine': Facts About the Mysterious Solar System World (Infographic)


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## Dennis E. Taylor (May 31, 2017)

It's not missing. It's taken up residence in the white house.

(runs away)


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## Alexa (May 31, 2017)

Everyhing missing can be found in area 51.


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## Venusian Broon (May 31, 2017)

I've posted this before years ago, but can't re-find the paper that stated this, but it has been suggested that there may be more planets in interstellar space than those orbiting stars. I believe the reasoning is that any arbitrary set of conditions that has a star forming with it's planetary accretion disc will, with high probability, be ejecting all sorts of material out of the disc - anything from gas giants, to ice and rocky worlds and loads of much smaller things*, as the disc forms a system until it exhausts it supply of material in the disc and leaves a system of 'trapped' planets in stable orbits.

The reason there could be more of them out in the cold of the interstellar space is that planets trapped in orbit around a star should have a tendency to coalesce and get bigger, hoovering up material, whereas at an earlier stage of disc evolution where we have lots of objects at, say, moon or earth sizes, that a fair proportion ,i.e. numerically a great many!, will be chucked out.

@Alexa That big Jupiter sized planets do move about weirdly can also be seen in some of the planetary systems which have 'hot Jupiters' - massive planets that are orbiting their star incredibly closely and can not have formed so close to the star - they must have spiralled in. Dynamically we know that there should be lots of configurations that could result in big Jupiter sized planets being ejected totally from a planetary system. 

As time has gone on they have actually found some candidates for rogue planets - planets wandering in interstellar space - at least some very large ones** (see Rogue planet - Wikipedia) - which does suggest (at least to me) that this hypothesis is correct.


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* Objects in near orbits, or orbits that intersect will interfere with each other resulting in collisions and orbital changes a la 'slingshot' manoeuvre. A slight increase in speed because of these interactions could see worlds being fired out of the system!

** Finding anything that hasn't a reliable internal heat source, is (cosmically) small and is very, very far away is of course very, very difficult. The fact that they have found some just floating about in interstellar space suggests therefore that there are a great many of them (we have just picked up the easiest ones that are very large, close enough that we can detect them, and have internal conditions that make them stand out) . Thinking about bell curves, I think we are picking up the high mass outliers, and that space should be awash with lots of objects - say earth-sized balls of rock and smaller - that are impossible to pick up with current science.

Of course some of these big rogue planets may just be tiny solar systems with very little material and the 'planet' is really a failed star.


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## Brian G Turner (May 31, 2017)

Venusian Broon said:


> it has been suggested that there may be more planets in interstellar space than those orbiting stars





Venusian Broon said:


> That big Jupiter sized planets do move about weirdly can also be seen in some of the planetary systems which have 'hot Jupiters' - massive planets that are orbiting their star incredibly closely and can not have formed so close to the star - they must have spiralled in.



Indeed, I remember when the first data on exoplanets started to come in and revealed a host of massive Jupiters - many very close to their stars. Later computer modeling suggested that one way this could happen was if the Jupiter-sized planets had formed further out, but slowly spiralled in - expelling any other planets in their way (and, of course, moons).

Ergo, space must be filled with wandering/rogue planets (and moons!). I sometimes wonder how much of the "missing mass" in galaxies could actually be accounted for by this. Additionally, I suspect the actual volume of gases and dust in the observable universe is far higher than we actually observe.


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## Vertigo (May 31, 2017)

Not sure it would be enough to account for the 'missing mass.' I believe there is more mass 'missing' than mass known about, and, since Jupiter, for example, is around 1000th the mass of the Sun, there would have to be 1000 Jupiters ejected from every stellar system in the universe to even make up the same amount of mass. Actually probably more since the Sun is not a particularly massive star.


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## Brian G Turner (May 31, 2017)

Oh, indeed - I don't mean the full amount as much as a significant fraction. Especially when gas and dust clouds are factored in.


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## reiver33 (May 31, 2017)

Gas giant? It was obviously orbital strip-mined into nothingness to fuel a passing Death Star...


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## Dave (May 31, 2017)

The fact the Venus and Uranus both spin in the opposite direction, points to them probably being turned upside-down in the past, most likely due to an impact. The eccentric orbit of Pluto similarly shows a cataclysmic event. Such large violent impacts would point to some very large bodies that were not in normal orbits, which itself possibly points to the breakup of a planet. All speculation, but interesting. 

There is thought to be a gravitational pull from somewhere in the Oort cloud that might be another planet, but it could just be the total mass of many, many smaller objects. I think that if there was another gas giant out there then we would now have found it (but you can never say that anything doesn't exist with certainty.)


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## J Riff (Jul 30, 2017)

It's well known where that mystery planet was when it blew up. Tweren't gas, it were dirt and rock, like this one we're on. It will surprise everyone, will make a great disaster movie trilogy.


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## BAYLOR (Jul 31, 2017)

Alexa said:


> Everyhing missing can be found in area 51.



I think it would be rather difficult for Area 51 to conceal a Gas giant.


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## Alexa (Jul 31, 2017)

As long as they keep it secret, who really knows ?


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## Alex The G and T (Jul 31, 2017)

It's only Plan 9 from outer space.


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## Cathbad (Jul 31, 2017)

I've been to Area 51; I can assure you nothing is there.



(It's all been moved to Area 86.)


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## Alex The G and T (Jul 31, 2017)

Suuuure, that's what They told you to say.


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## Cathbad (Jul 31, 2017)

I am being honest!

...and pay no attention to the man behind that curtain, holding the microphone and  wearing the headset!


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## farntfar (Jul 31, 2017)

The planet was called Poosch and it's gone looking for its lost moon.


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## Mirannan (Jul 31, 2017)

Brian G Turner said:


> Indeed, I remember when the first data on exoplanets started to come in and revealed a host of massive Jupiters - many very close to their stars. Later computer modeling suggested that one way this could happen was if the Jupiter-sized planets had formed further out, but slowly spiralled in - expelling any other planets in their way (and, of course, moons).
> 
> Ergo, space must be filled with wandering/rogue planets (and moons!). I sometimes wonder how much of the "missing mass" in galaxies could actually be accounted for by this. Additionally, I suspect the actual volume of gases and dust in the observable universe is far higher than we actually observe.



Probably right in both cases. However, IIRC the amount of baryonic dark matter (i.e. dark matter made out of stuff we recognise) cannot be more than about 10% of the missing mass. I don't pretend to understand the detailed reasons, but apparently the abundance of various nuclei (specifically lithium and deuterium, and to a certain extent boron, carbon, nitrogen and oxygen) would be greatly different from observed if there was more baryonic dark matter than that.

This covers some of it, but (fair warning!) it's pretty horrible unless you're a cosmologist:

Dark Matter Limit


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