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Researchers Find Evidence Of Distant Outer Planet
HSchirmer
post Jan 21 2016, 03:33 PM
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QUOTE (Mongo @ Jan 20 2016, 05:58 PM) *
Free to view paper:

Evidence for a Distant Giant Planet in the Solar System
Konstantin Batygin and Michael E. Brown

QUOTE

In this work we show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space.
We demonstrate that the perihelion positions and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007% to be due to chance, thus requiring a dynamical origin.
We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass -10x earth- whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180 away from the perihelia of the minor bodies.




Very interesting- basically a "balance argument"?
The lopsided grouping of known eccentric KBO orbits implies a counter balancing object in an eccentric orbit.
We likely can't see this object because it is currently hidden by the bright backdrop of the milky way.

Ok, what about a "null hypothesis" -
The lopsided grouping of known eccentric KBO orbits implies that KBOs are equally distributed around the solar system, but because of an observation bias, we have detected those that are against a dark sky, but have not detected those that are masked by the milky way?

Does the subset "known eccentric KBO orbits" imply
the set "unknown equally distributed eccentric KBO orbits" or does it imply "single large planet in eccentric orbit"?

Curious about the orbital mechanics, if we find eccentric KBO orbits with argument of perihelion going the opposite way, towards the milkly way, would that imply a Planet IX with a circular orbit?
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alan
post Jan 21 2016, 04:34 PM
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QUOTE
Ok, what about a "null hypothesis" -
The lopsided grouping of known eccentric KBO orbits implies that KBOs are equally distributed around the solar system, but because of an observation bias, we have detected those that are against a dark sky, but have not detected those that are masked by the milky way?

Figure 2 of the paper shows the distribution of perihelia, those used in the paper are distributed over 110 degrees of elliptic longitude, so I would expect at least some of those with perihelia in the opposite direction to miss the milky way.
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ZLD
post Jan 21 2016, 04:35 PM
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Wasn't the VLT paper just last month getting lambasted with many maintaining that there couldn't be a planet of this size left undiscovered in the solar system because surveys should have caught them? Why is this being lauded so highly if the same reasoning should still apply? Don't get me wrong, I find both intriguing and somewhat compelling and worthy of further research.


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scalbers
post Jan 21 2016, 05:15 PM
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QUOTE (tfisher @ Jan 21 2016, 06:46 AM) *
Wow. If we launch a probe that goes at similar speed to voyager 1, it takes over 100 years to reach 400 AU. From the blog site, it sounds pretty likely this thing is sitting out near its aphelion. Seems like a multi-generation effort is needed to explore this.

Unless we can resurrect the "Planet Imager" mission concept of a constellation of space interferometers. This next step to network several Terrestrial Planet Finder (TPF) systems was envisioned to image details on planets around other stars, though maybe it can be repurposed?

Also, maybe new rocket technology will come along at some point if we want to speculate on that.

Will a telescope like the LSST be able to locate this planet? And does this really clear out its orbit to qualify as a planet?


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JRehling
post Jan 21 2016, 05:16 PM
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QUOTE (Phil Stooke @ Jan 20 2016, 10:15 PM) *
I'm waiting until I can make a map of it before I accept it as real.


Here there be dragons.
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stevesliva
post Jan 21 2016, 05:27 PM
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QUOTE (ZLD @ Jan 21 2016, 11:35 AM) *
Wasn't the VLT paper just last month getting lambasted


I don't recall that, and I'm always interested in how people benchmark their skepticism as well. I do recall lambasting of the alpha centauri serendipitous discovery that wasn't.
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Mongo
post Jan 21 2016, 06:06 PM
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QUOTE (scalbers @ Jan 21 2016, 06:15 PM) *
Will a telescope like the LSST be able to locate this planet? And does this really clear out its orbit to qualify as a planet?


That definition uses very unfortunate wording. A planet does not literally have to clear away all other objects close to its orbit. If that were so there would be NO planets in the Solar System (except maybe Mercury or Venus). Another equally acceptable wording is that a planet must gravitationally dominate its neighborhood, which does apply to all eight known planets in the Solar System, but not to any of the known dwarf planets. It appears that this "Planet Nine" would gravitationally dominate its neighborhood (indeed, that was how its existence was theorized), so it would qualify as a full planet.
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Explorer1
post Jan 21 2016, 06:48 PM
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Margot's 2015 paper criteria ( http://arxiv.org/pdf/1507.06300.pdf ) is what Mike Brown relies upon for his nomenclature decision, posted on the new blog: http://www.findplanetnine.com/2016/01/is-p...ine-planet.html
Maybe that should be the last word on this specific topic, given the current forum rules.... wink.gif
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JRehling
post Jan 21 2016, 07:43 PM
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Two noteworthy sentences in the article:

"No obvious bias appears to cause the observed clustering."
"the precise range of perturber parameters required to satisfactorily reproduce the data is at present difficult to diagnose."

There's a lot being assumed there. I suppose all research has an implication like that behind it, but it leaves the conclusion in a vague realm: Of the things we've considered, one of them best explains the data.

There's a discussion of some biases, and it's noted that one aspect of the data could not be the result of observational bias. I'm not sure how much of the argument that applies to, and what parts of the argument that does not apply to. It seems clear that there's something unusual about the data that remains unexplained, but it's unclear how much the argument hinges on that powerful word "obvious" the possibility that an un-obvious bias (i.e., any of the infinite number of possibilities that weren't considered) might explain it without the hypothesized ninth planet.

There's a lot of work left to do here, and I think the authors are clear about this. If someone can turn their analysis into a focused observational program looking for the ninth planet, that's great, but I think there's a lot more theorizing left to do, and the argument for a ninth planet might vanish by the time the pen-and-paper work is done.
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Caotico09
post Jan 21 2016, 11:17 PM
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QUOTE (ZLD @ Jan 21 2016, 10:35 AM) *
Wasn't the VLT paper just last month getting lambasted with many maintaining that there couldn't be a planet of this size left undiscovered in the solar system because surveys should have caught them? Why is this being lauded so highly if the same reasoning should still apply? Don't get me wrong, I find both intriguing and somewhat compelling and worthy of further research.


This Blog talks a little about surveys and what areas of Planet Nine's orbit have been looked at:

http://www.findplanetnine.com/p/blog-page.html
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surbiton
post Jan 22 2016, 03:24 AM
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QUOTE (Gerald @ Jan 20 2016, 06:35 PM) *
That far out the Hill sphere of an object should be rather large. Therfore I'm wondering - provided the analysis isn't based on observational bias - whether there couldn't exist kind of a miniature globular cluster made of planetesimals, or a small version of a protoplanetary disk, of the same mass as the presumed planet, but without having formed an actual planet.
The simulations - as far as I understood - assume a certain point mass, but not necessarily united to one planet.
Or - if there is one population of KBOs - why not a second one, forming a Kozai-like resonance with the observed population.


That sounds like the most plausible explanation. I also read that it is supposed to be rocky. I am not sure how that can be known.
A "mass" can be gaseous too, however, this is in the belt Surely, one "planet" would have been detected by now ?
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surbiton
post Jan 22 2016, 03:36 AM
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QUOTE (Mongo @ Jan 21 2016, 06:06 PM) *
That definition uses very unfortunate wording. A planet does not literally have to clear away all other objects close to its orbit. If that were so there would be NO planets in the Solar System (except maybe Mercury or Venus). Another equally acceptable wording is that a planet must gravitationally dominate its neighborhood, which does apply to all eight known planets in the Solar System, but not to any of the known dwarf planets. It appears that this "Planet Nine" would gravitationally dominate its neighborhood (indeed, that was how its existence was theorized), so it would qualify as a full planet.


Would that mean dear Pluto is back as a planet ? Whooopie !
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JRehling
post Jan 22 2016, 03:39 AM
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Gravity follows an inverse square law. If a collection of independent objects had enough mass to influence objects far (>1 AU) away, it would certainly have enough mass to congeal quite rapidly in geological time. It would be pulling itself together much more than it would be exerting subtle tugs on other objects.

The presumption that the object is rocky is simply a comment, I think, on whether it has enough mass to have collected a gaseous component like Neptune or not. There isn't any direct evidence as the composition (e.g., rock vs. metal vs. ice). Nor, in fact, any direct evidence about this body's actual existence.
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Gerald
post Jan 22 2016, 11:49 AM
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Globuar clusters are billions of years old and of considerable mass. So I'm not sure, whether it's straightforward, that clusters of debris need to congeal rapidly, if sufficiently distant from the Sun.
Kozai oscillations happen in small steps over many orbits.

Edit: That far out this could imply, that despite the whole cluster being, e.g. of 10 Earth masses, the largest object may still be considerably lighter.
As a consequence it may not be able keep a helium/hydrogen atmosphere. Other volatiles would be frozen, leading to a potentially comet-nucleus-like low albedo surface, hence reduced visual brightness.
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Julius
post Jan 22 2016, 12:16 PM
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QUOTE (surbiton @ Jan 22 2016, 04:36 AM) *
Would that mean dear Pluto is back as a planet ? Whooopie !

It would mean that the solar system has got 2 belts, the asteroid belt between Mars and Jupiter and the Kuiper belt between Neptune and what lies beyond such as planet 9.
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