Part of the background of the complexity here is the high number of possible scenarios to model.

The possible scenarios involving a single large planet as the explanation allow for variation in several variables. The planet's mass is one variable and its orbit entails about three more. Ideally, modeling work could investigate a large number of the possible permutations, iterating over the range of possible values in a fine-grained way. To model the evolution of the outer solar system over eons in each of thousands of different scenarios is a feat requiring sheer CPU time, and that work certainly ought to be done. Then, we might learn if there are any combination of parameters that explain the observations, and which cannot do so. Examining only one, or even only 100, of the possibilities is just scratching the surface of the possibilities. Nobody, novice or professional, is going to work this out with mere deep thought.

The general orbit requires six parameters to describe it. If you assume it's orbital plane is close to the ecliptic that's still four parameters.

Of course your point is well taken - it's going to be really hard to thoroughly explore that parameter space.

There was a SETI talk by dr Ann-Marie Madigan. She had a simulation that could explain the Sedna objects strange orbits with smaller object (but still with 1-10 total earth masses):

http://www.seti.org/weeky-lecture/bizarre-...-beyond-neptune

Available on Youtube.

Can't see if she written any paper about it.

OK, paper has been up for a while,http://arxiv.org/abs/1509.08920 - Brown/Konstantin references it.

Only news is that a nice talk about it became available this week.

Even if the inclination instability model was correct, there could still be one or more objects with planetary mass in the outer solar system. Ceres contains a third of the mass in the asteroid belt and while the case may not be so severe in a large disk, when dealing with a disk of one or more earth masses, you will start reaching planetary masses rather quickly. There could be subjects ranging from Mercury to Mars and greater. I've read before that if Ganymede and Titan would be considered planets if they orbited the sun. That was then, now if we find larger objects out there, wouldn't they still be called planets?

FWIW, Ganymede and Titan have larger diameters than Mercury but less than half its mass.

I'm not sure of any way in which considering a thing a planet or not is relevant except in the circular sense of its own sake.

For something to be producing the effects that have been discussed here, it would almost certainly have to be much more massive than Ganymede; probably more massive than Earth, which itself is dozens of times the mass of Ganymede.

MOD NOTE: Let's please not drift into the endlessly contentious topic of 'what is a planet'; see rule 1.9.

More constraints on the possible orbit:

Coralling a distant planet with extreme resonant Kuiper belt objects
Renu Malhotra, Kathryn Volk, Xianyu Wang

http://arxiv.org/abs/1603.02196

Clever with consideration of resonances. It appears they are just about telling us where we can actually look.

Yep, most likely seems to be 600 AU out in the constellation Cetus.
Looks like a bit of luck, a dark energy survey scope is already looking in that area.

Hey, I'm curious, has anybody created a Planet 9 orbit for Celestia?
It looks like thats what Batgin & Brown used for their orbit illustration.

Hmm, is it possible to draw the space of possible orbits for Planet 9 as a torus in Celestia?

Well, plugging in some rough numbers,




somewhere along the red line


Hmm, still have to tweak those parameters, that does generate a track which is similar to other published paths,
but when you zoom out, Planet 9 is on the same side as Sedna.

An author at Centauri-Dreams.org started the ball rolling on what kind of technology could be used for a theoretical mission to Planet 9. A probe moving at New Horizons 4-2.5 AU/year would need centuries to arrive - a 10 fold increase in velocity is going to be needed for a probe to arrive in a "reasonable" (20-30 year) time.

I think this paper is likely to run into difficulty clearing the peer review process. There should be some statistical significance analysis and they don't attempt that, or offer an explanation why. They give five orbital period ratios and conclude that their proximity to certain small integer ratios is "intriguing." This includes 6.115 being "close to" 6/1. Well, 23% of all real numbers are that close to a N:1 ratio and most real numbers are that close to an N:1, N:2, or N:3 ratio.

A lot of things are "intriguing" but in statistical work, you try to establish significance, and I don't see a good excuse for not trying to do so.

They may have begun the work that would lead to a really compelling result: Some of those period ratios look much closer to significance than the one I've criticized. This just looks like an incomplete piece of work as it's been posted.

to go with "HSchirmer" post #55
way back i posted a texture for the "ninth" - maybe ? planet
post #2
http://forum.celestialmatters.org/viewtopi...p?f=2&t=804
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Following up on dtol man, today's laser sail announcement might be a way to get to P9 (if P9 is real of course) within the lifespans of us UMSFers.
The mention of a 1/100 prototype near the bottom of this post is far more plausible to me than just a straight shot to Alpha. P9 would be a great intermediate destination....
http://www.centauri-dreams.org/?p=35402
Some numbers the group provides for our own solar system here:
http://breakthroughinitiatives.org/Target/3

Absolute waste of time right now until these hypothetical engines make it feasible IMO, we might aswell shoot for other stars cause 600au is a fraction of the distance (albeit small). Money is better spent on researching telescopes that would be sensitive to view in a decent resolution. None of us would be alive if a probe took off today heading at Pioneer Speeds would take to long.

For whatever reason NASA is not very interested or not funded enough to seriously pursue new propulsion. Other than Ion Drive & Gravity Assist, nothing has innovated since the 1960's.