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Unmanned Spaceflight.com _ Telescopic Observations _ Researchers Find Evidence Of Distant Outer Planet
Posted by: Mongo Jan 20 2016, 04:58 PM
Free to view paper:
http://iopscience.iop.org/article/10.3847/0004-6256/151/2/22/meta
Konstantin Batygin and Michael E. Brown
Recent analyses have shown that distant orbits within the scattered disk population of the Kuiper Belt exhibit an unexpected clustering in their respective arguments of perihelion. While several hypotheses have been put forward to explain this alignment, to date, a theoretical model that can successfully account for the observations remains elusive. 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 gsim10 m⊕ 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. In addition to accounting for the observed orbital alignment, the existence of such a planet naturally explains the presence of high-perihelion Sedna-like objects, as well as the known collection of high semimajor axis objects with inclinations between 60° and 150° whose origin was previously unclear. Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet.
To date, the distinctive orbital alignment observed within the scattered disk population of the Kuiper Belt remains largely unexplained. Accordingly, the primary purpose of this study has been to identify a physical mechanism that can generate and maintain the peculiar clustering of orbital elements in the remote outskirts of the solar system. Here, we have proposed that the process of resonant coupling with a distant, planetary mass companion can explain the available data, and have outlined an observational test that can validate or refute our hypothesis.
We began our analysis with a re-examination of the available data. To this end, in addition to the previously known grouping of the arguments of perihelia (Trujillo & Sheppard 2014), we have identified ancillary clustering in the longitude of the ascending node of distant KBOs and showed that objects that are not actively scattering off of Neptune exhibit true orbital confinement in inertial space. The aim of subsequent calculations was then to establish whether gravitational perturbations arising from a yet-unidentified planetary-mass body that occupies an extended, but nevertheless bound, orbit can adequately explain the observational data.
The likely range of orbital properties of the distant perturber was motivated by analytic considerations, originating within the framework of octupole-order secular theory. By constructing secular phase-space portraits of a strictly planar system, we demonstrated that a highly eccentric distant perturber can drive significant modulation of particle eccentricities and libration of apsidal lines such that the perturber's orbit continuously encloses interior KBOs. Intriguingly, numerical reconstruction of the projected phase-space portraits revealed that, in addition to secular interactions, resonant coupling may strongly affect the dynamical evolution of KBOs residing within the relevant range of orbital parameters. More specifically, direct N-body calculations have shown that grossly overlapped, apsidally anti-aligned orbits can be maintained at nearly Neptune-crossing eccentricities by a highly elliptical perturber, resulting in persistent near-colinearity of KBO perihelia.
Having identified an illustrative set of orbital properties of the perturber in the planar case, we demonstrated that an inclined object with similar parameters can dynamically carve a population of particles that is confined both apsidally and nodally. Such sculpting leads to a family of orbits that is clustered in physical space, in agreement with the data. Although the model proposed herein is characterized by a multitude of quantities that are inherently degenerate with respect to one another, our calculations suggest that a perturber on an a' ~ 700 AU, e' ~ 0.6 orbit would have to be somewhat more massive (e.g., a factor of a few) than m' = 10 m⊕ to produce the desired effect.
A unique prediction that arises within the context of our resonant coupling model is that the perturber allows for the existence of an additional population of high-perihelion KBOs that do not exhibit the same type of orbital clustering as the identified objects. Observational efforts aimed at discovering such objects, as well as directly detecting the distant perturber itself constitute the best path toward testing our hypothesis.
So about the size of Neptune, if their hypothesis is correct.
Posted by: scalbers Jan 20 2016, 05:29 PM
This sounds familiar, perhaps written about recently in Sky and Telescope?
http://www.skyandtelescope.com/astronomy-news/new-object-offers-hint-ofplanet-x/
EDIT: I found the 2014 article above online - though I probably read a similar thing in the magazine.
Posted by: Steve G Jan 20 2016, 05:43 PM
Help me out here on the math. If they are mentioning 700 AU (correct me if I'm wrong please) and Voyager 1 is currently 133.8 AU, and is considered to be in interstellar space, and this is 5 times more distant, is it really a planet or an interstellar companion?
Posted by: Explorer1 Jan 20 2016, 05:45 PM
scalbers: I recall that would have been about the 2014 results for the first KBO grouping; the second grouping being exactly where the models predict seals the deal as far as the paper is concerned. Exciting stuff.
It still needs to be actually spotted, of course (and then work can start on New Horizons 2 for real this time!).
Posted by: JRehling Jan 20 2016, 06:19 PM
63,000 AU is one light year, and is approximately the radius of the Sun's Hill sphere. This is therefore only about 1% of the size of the largest orbits that are possible around the Sun, and only 0.25% of the distance to the nearest other star. So this doesn't seem very interstellar to me. On the interstellar scale, this object (if it exists) is right next to the Sun.
Perhaps more to the point, the observed dynamic, if it exists, depends upon the object having made many orbits around the Sun, not being something out there floating in its own orbit around the galaxy.
Posted by: 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 https://en.wikipedia.org/wiki/Kozai_mechanism-like resonance with the observed population.
Posted by: stevesliva Jan 20 2016, 06:42 PM
Mike Brown's blog hinted that he was trying to explain Sedna's weird orbit. This would be that, but I don't think the details have been previously explained.
Posted by: katodomo Jan 20 2016, 06:56 PM
700 AU is given as an example semi-major axis of a perturber, with from a cursory glance their possible range laying at 400 to 1500 AU semi-major axes. The minor planets cited as grouped by resonance with the hypothetical objext have semi-major axes of 150-600 AU.
What NASA used as definition for the solar system for Voyager is the heliosphere, i.e. the extend to which the stellar wind of the Sun interferes with the interstellar medium; an object with aphelion (such as most long-period comets) beyond basically dips in and out of this bubble. The IAU definition of a planet does not have any distance limitation.
The referred-to Hill Sphere of the Sun, being its gravitational influence zone, is probably the most appropriate measure when considering "interstellar companions" though.
Posted by: Gladstoner Jan 20 2016, 10:54 PM
I recall reading somewhere about an observed (possible) clustering of long-period cometary orbits that could have resulted from a distant massive planet or even a brown dwarf (which has since been ruled out). It would be interesting to compare these with the findings of Batygin-Brown.
Posted by: Holder of the Two Leashes Jan 20 2016, 11:35 PM
So about the size of Neptune, if their hypothesis is correct.
Neptune has a mass about 17.15 earths, so a factor of "a few" time ten earths sounds to me like something bigger than Neptune, even if "a few" means three or four.
Neptune would have been visible to WISE out to 700 au. Saturn, at 95 earth masses, out to 10,000 au. This hypothesized planet somewhere in between. So... just how eccentric an orbit are we talking here?
Posted by: 0101Morpheus Jan 20 2016, 11:37 PM
Gladstoner.
I was under the impression that the such ruled out any brown dwarf or massive planets currently around the sun. There could have been one out there once and was since lost. Or maybe an interstellar interloper made a close pass to the solar system and went on its way.
Posted by: elakdawalla Jan 21 2016, 12:34 AM
Most of the answers to all of your questions can be found on http://www.findplanetnine.com/p/blog-page.html.
Posted by: scalbers Jan 21 2016, 12:43 AM
I believe what I had read about in Sky and Telescope magazine is the clustering of arguments of perihelion of KBO's. It was suggested in 2014 in an online S&T article these correlations of perihelia could be consistent with a distant planetary perturbation (a super-Earth around 250AU distant). I'm a bit unclear on whether what I'd read was in Emily's S&T print article from Feb 2014 or more likely another writeup a bit more recently. I added a relevant link into post #2. Explorer1 summarizes this also in post #4.
Posted by: Phil Stooke Jan 21 2016, 05:15 AM
I'm waiting until I can make a map of it before I accept it as real.
Phil
Posted by: 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.
Posted by: HSchirmer Jan 21 2016, 03:33 PM
Evidence for a Distant Giant Planet in the Solar System
Konstantin Batygin and Michael E. Brown
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?
Posted by: alan Jan 21 2016, 04:34 PM
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.
Posted by: ZLD Jan 21 2016, 04:35 PM
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.
Posted by: scalbers Jan 21 2016, 05:15 PM
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?
Posted by: JRehling Jan 21 2016, 05:16 PM
Here there be dragons.
Posted by: stevesliva Jan 21 2016, 05:27 PM
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.
Posted by: 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.
Posted by: Explorer1 Jan 21 2016, 06:48 PM
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-planet-nine-planet.html
Maybe that should be the last word on this specific topic, given the current forum rules.... 
Posted by: JRehling Jan 21 2016, 07:43 PM
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.
Posted by: Caotico09 Jan 21 2016, 11:17 PM
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
Posted by: surbiton Jan 22 2016, 03:24 AM
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 https://en.wikipedia.org/wiki/Kozai_mechanism-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 ?
Posted by: surbiton Jan 22 2016, 03:36 AM
Would that mean dear Pluto is back as a planet ? Whooopie !
Posted by: JRehling Jan 22 2016, 03:39 AM
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.
Posted by: Gerald Jan 22 2016, 11:49 AM
https://en.wikipedia.org/wiki/Globular_cluster are billions of years old and of considerable mass. So I'm not sure, whether it's straightforward, that clusters of debris need to https://en.wikipedia.org/wiki/Globular_cluster#Mass_segregation.2C_luminosity_and_core_collapse rapidly, if sufficiently distant from the Sun.
https://en.wikipedia.org/wiki/Kozai_mechanism#Timescale 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.
Posted by: Julius Jan 22 2016, 12:16 PM
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.
Posted by: Mongo Jan 22 2016, 12:20 PM
Nope. Pluto is far too small to have any significant gravitational effect on other objects in similar orbits. It's merely one of numerous bodies of similar or slightly smaller size in its region of the Solar System, none of which are gravitationally significant. The dominant mass in its region is Neptune, which does control which orbits around it are occupied and which are empty, through resonances. The possible "Planet Nine", on the other hand, would count as a full planet because of its huge gravitational impact on everything in its region of the Solar System.
Posted by: scalbers Jan 22 2016, 05:38 PM
On the other hand, planet 9 would be near the borderline of planethood, based on the graph we've seen in the 2015 Margot paper and in this blog:
http://www.findplanetnine.com/2016/01/is-planet-nine-planet.html
Posted by: HSchirmer Jan 22 2016, 07:14 PM
http://www.findplanetnine.com/2016/01/is-planet-nine-planet.html
The graph mentioned above illustrates an interesting point, " a planet clearing its orbit" IS actually a function of time AND mass. So the smaller bodies just take longer to BECOME planets.
It seems like Planet-9's current location would be the result of Jupiter or Saturn clearing IT out of THEIR orbit.
INSTABILITY-DRIVEN DYNAMICAL EVOLUTION MODEL OF A PRIMORDIALLY 5 PLANET OUTER
SOLAR SYSTEM
http://arxiv.org/pdf/1111.3682v1.pdf
Several runs of Nice Model simulations suggest that an ice giant between Saturn and Uranus would be the
most likely planet to be ejected.
Rather odd, then, that it WAS NOT a planet when it was being ejected from the orbital path of a gas giant,
then it becomes a planet when it clears out the area where it has been ejected to.
Posted by: JRehling Jan 22 2016, 07:26 PM
This paper, Trujillo and Sheppard (2014), is so important to the discussion, that it should be read by anyone trying to understand the new work:
http://home.dtm.ciw.edu/users/sheppard/pub/TrujilloSheppard2014.pdf
It gives details of the key observation, that among minor planets with q>30 AU, the 12 objects with a>150 AU show common orbital characteristics that are not seen among the larger population of objects with q>30 AU and a<150 AU. 12 is sufficient to show statistical significance, so, simply put, there is something here that needs to be explained.
I think we need to see more work considering alternative explanations before a planetary perturber stands out as the only good explanation. Some things the two papers note:
1) Observational biases may exist, but can't explain all of the orbital similarities.
2) An origin based solely in the initial conditions of the outer solar system would not survive gigayear exposure to torques caused by the known outer planets.
Remaining models consist of various combinations of one or more perturbing objects orbiting the Sun combined possibly with some close stellar interaction in the past.
A difficulty is that the number of possible combinations of those models is wildly unconstrained. Finding a model that matches the observations pretty well isn't going to eliminate the infinite number of possible explanations that weren't considered. So, I think we're a long way from being able to duplicate the success of Neptune's discovery, where careful analysis gives astronomers a pinpoint location in the sky where the unseen object must exist.
Posted by: JRehling Jan 22 2016, 09:11 PM
Funny, yet thought-provoking:
Possible Undiscovered Planets
http://xkcd.com/1633/
Posted by: vossinakis Jan 25 2016, 09:24 AM
Are you referring to this??? Arguments for the presence of a distant large undiscovered Solar system
planet http://astro.u-szeged.hu/ismeret/murray.pdf
Posted by: Floyd Jan 26 2016, 12:40 AM
The latest Scientific American has an article on the search for planet X---by Michael Lemonick. Article good as background for this thread.
Posted by: TheAnt Jan 27 2016, 02:55 PM
Oh yes I did run into that SciAm article also, before reading it I considered this to be one interesting idea but one that might have other explanations.
However when seeing http://www.scientificamerican.com/sciam/assets/Image/P9_KBO_extras_orbits_labeled.jpg graphic with orbits of KBO's that are far from the ecliptic I began to understand why they find this such an tantalizing possibility.
Still when considering a planet like Neptune it should have an atmosphere that's gaseous even in the cold realm so far from the Sun. One such should show an IR excess for one or another reason, latent heat released when gas turning liquid and rain down for example. Now actually finding it might depend where this putative planet is located in its orbit, if it's anywhere of the furthest part of the orbit right now, the distance and very small proper motion might make it very difficult to detect. So yes, perhaps, they might be onto something here - yet, saying 'evidence' is stretching the meaning of the word a little bit to far yet. 
Posted by: jasedm Jan 27 2016, 07:03 PM
I agree. Evidence there isn't (as yet)
Posted by: fredk Jan 27 2016, 09:04 PM
Agreed. Possibly "indirect evidence" or "circumstantial evidence", with the caveat already mentioned here that an "unobvious bias" may also explain the observations. "Theoretical evidence" also doesn't make sense, since theories aren't observations and so can't provide evidence!
In my business, we'd probably call it a "hint".
Posted by: Habukaz Jan 27 2016, 11:00 PM
It's easy for a definition of the word evidence to be circular:
a) evidence is http://www.merriam-webster.com/dictionary/evidence
b) we know that something exists because we have evidence for its existence
So in order to know if something counts as evidence towards something, we first have to know if that something is real, and in order to know if something is real, we need evidence..
I think I'd rather put it this way: evidence is an observation consistent with a hypothesis, regardless of whether we assume the hypothesis to be true or false.
(now, you could say that evidence is part of what convinces you that something is real, but the subjectivity of this would make the definition problematic)
So I'd finally say that there is evidence - "inconclusive" evidence - for a fifth giant planet in the solar system. The consensus would also appear to be that not (good) enough evidence has been presented yet for this case in order to get really excited about it.
Posted by: Floyd Jan 27 2016, 11:45 PM
We have the original data in the orbital parameters of several KBOs. Trying to explain the unusual clustering of these orbits, the idea of a 9th planet seemed a possibility. Much experimentation with computer modeling found a planet 9 mass and general orbit that could cause such clustering. Now there is a hypothesis. To test the hypothesis requires new data(KBOs) or spotting planet 9. The original data for a hypothesis can't be used as evidence for that hypothesis--must get new data.
Posted by: HSchirmer Jan 28 2016, 12:47 AM
...
I think I'd rather put it this way: evidence is an observation consistent with a hypothesis, regardless of whether we assume the hypothesis to be true or false.
...
There are a few other definitions, the one I'm familiar with is logic/legal.
Evidence is anything that helps to prove or disprove an ultimate fact.
In much the same way that you have equations and variables, you also have law (hypothesis) and facts.
Facts are usually variables, unknowns that can be established or measured.
A series of facts, combined with an argument, eventually gets you to a proof.
Posted by: nprev Jan 28 2016, 01:39 AM
MOD NOTE: Enough with the semantics, please.
Posted by: Gerald Jan 28 2016, 09:56 AM
Citing http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system:
The range between 3 and 5 sigma is usually called "evident", greater or equal 5 sigma is called "definitive". 3 < 3.8 < 5. That's all.
The question is essentially, whether the numerical experimental settings leading to these 3.8 sigma confidence level are consistent with the way astronomers would have looked for the KBOs, hence whether the observational bias is considered appropriately.
One issue might be, that the same arguments preventing the direct observation of a possible planet 9 prevented observations of KBOs, e.g. the densely crowded Milky Way background.
Another issue might be an adjustment of the observation and detection methods to the first observed KBO of the presumed cluster. This disturbs the independence of the individual finds, as assumed in most randomized statistical tests, hence modifies inferred probabilities, and eventually the confidence level.
Edit: Another example: The probability of six objects randomly found in the same predefined 0.203 fraction of the sky is 7e-5 (the 3.8 sigma); the probability of six objects randomly found in the same predefined 0.379 fraction of the sky is 3e-3 (3.0 sigma). Hence another uncertainty is the size of the region of the sky the six observations are assigned to.
Posted by: JRehling Jan 28 2016, 11:09 AM
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.
Posted by: fredk Jan 28 2016, 03:09 PM
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.
Posted by: Anders Jan 31 2016, 08:43 PM
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-orbits-minor-planets-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.
Posted by: 0101Morpheus Feb 4 2016, 11:31 PM
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?
Posted by: JRehling Feb 5 2016, 12:52 AM
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.
Posted by: nprev Feb 5 2016, 12:28 PM
MOD NOTE: Let's please not drift into the endlessly contentious topic of 'what is a planet'; see rule 1.9.
Posted by: selden Mar 26 2016, 01:56 PM
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
Posted by: scalbers Mar 26 2016, 03:11 PM
Clever with consideration of resonances. It appears they are just about telling us where we can actually look.
Posted by: HSchirmer Apr 10 2016, 01:37 PM
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?
Posted by: HSchirmer Apr 10 2016, 06:51 PM
Well, plugging in some rough numbers,
{
Class "planet"
Texture "neptune.jpg"
Color [ 0.65 0.45 0.35 ]
Radius 14000 # rough guess
EllipticalOrbit {
Period 15000
SemiMajorAxis 700
Eccentricity 0.6
Inclination 30
AscendingNode 90
ArgOfPerihelion 150
MeanAnomaly 0
Albedo 0.15
Epoch 2456800.5
}
}
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.
|
Posted by: dtolman Apr 11 2016, 03:25 PM
An author athttp://www.centauri-dreams.org/?p=35392 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.
Posted by: JRehling Apr 11 2016, 04:30 PM
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.
Posted by: JohnVV Apr 12 2016, 03:09 AM
to go with "HSchirmer" post #55
way back i posted a texture for the "ninth" - maybe ? planet
post #2
http://forum.celestialmatters.org/viewtopic.php?f=2&t=804
----------
http://imgbox.com/AFsJUFfz
Posted by: Explorer1 Apr 12 2016, 04:51 PM
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
Posted by: Steve5304 Apr 12 2016, 06:28 PM
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.
Posted by: JRehling Apr 12 2016, 11:40 PM
The lack of innovation has been discussed and largely rebutted here:
http://www.unmannedspaceflight.com/index.php?showtopic=7842
Posted by: dtolman Apr 13 2016, 11:18 AM
With the electric-ion engines we have now - isn't the issue just finding a powersource that we can pair up with it to provide thrust for the necessary length of time?
Posted by: nprev Apr 13 2016, 11:39 AM
MOD NOTE: Let's please stay on topic.
Posted by: AJAW May 2 2016, 02:52 PM
Two relevant things:
First, Mike Brown and Konstantin Batygin comment on the Malhotra, Volk & Wang ArXiv e-print here:
http://web.gps.caltech.edu/~mbrown/papers/ps/findp9.pdf
(Near the end of the paper.) Their final relevant sentence is this: “Thus, it appears that no useful constraint on the orbit or position can be drawn from this method.”
I’m not qualified to evaluate the arguments, but from their blog postings I’ve formed the impression that Brown & Batygin are very competent and cautious scientists and I’m biased in their favour. 
The second thing is something that I discovered when I was fortunate enough to attend the British Astronomical Association one-day meeting on Robotic exploration of the Solar System on the 30th
April. (Incidentally James Canvin of UMSF gave a great talk on “Amateur use of Solar System spacecraft data”.) What attracted my notice Planet Nine-wise was a talk by Prof. Mark McCaughrean
on ESA’s Solar System exploration programme. (He is the Senior Science Advisor in the Directorate of Science & Robotic Exploration at ESA.) When talking about the Gaia astrometry mission,
he mentioned that the gravitational lensing effects of the sun and planets have to be removed as part of the data processing – the sun’s effects are practically 360 degree, and those for Jupiter are
very large, but I believe they do it for all the planets.
After the talk, I asked him if they could potentially detect the gravitational lensing effects of Planet Nine. He thought that they probably could – if they already knew where it was!
However, he thought that the volume of the data and the small signal would make it very difficult to extract without knowing where to look.
He was answering after just a few seconds thought, and I still wonder if there might be some hope in this method – after all, we should be able to calculate roughly what the lensing signal
would look like, and it’s moving, so Gaia, with multiple observations of the same patches of sky, should have observations with and without the planet, at multiple locations that have a
roughly predictable separation from each other. But I don’t know anything about the signal to noise ratio, or the data set. For a billion stars, I guess it’s pretty big!
Can anyone give a more informed opinion on this?
Posted by: Phil Stooke May 2 2016, 03:41 PM
This would make a good test of the laser propulsion and data collection technology promoted recently for Alpha Centauri, as Explorer 1 already noted.
Phil
Posted by: Gerald May 2 2016, 04:00 PM
For visual magnitude 14 stars, http://arxiv.org/abs/astro-ph/0409531 (muas).
If my calculation is correct, that's pi/(180° x 1e5 x 3600) = 4.848e-11 in radians.
The Schwarzschild radius for a 1e25 kg mass (about twice the mass of Earth) should be 2GM/c² = 14.8 mm. Use this to calculate the https://en.wikipedia.org/wiki/Gravitational_lens#Explanation_in_terms_of_space.E2.80.93time_curvature, and resolve the equation to the radius r = 0.0148 m / (2 x 10 muas) = 0.0148 m / 4.848e-11 = 153122 km = 1.02e-3 a.u. (astronomical units).
For a mass at 1000 a.u. distance that's an apparent angle (in radians) of about 1.02e-3 a.u./1000 a.u = 1.02e-6.
With https://en.wikipedia.org/wiki/Gravitational_lens#Explanation_in_terms_of_space.E2.80.93time_curvature, we get an angle (in radians) of (0.66° x pi / 180°)/1966 = 5.86e-6 per pixel.
Hence the displacement of background stars of magnitude 14 by a 1e25 kg mass at 1000 a.u. distance would be detectable using mag 14 stars within a radius of about 1/5 pixel around the CCD position of the (theoretical) image of the mass.
This would be extremely difficult. For a larger mass at closer distance it would look more realistic.
Posted by: fredk May 2 2016, 07:39 PM
Taking the number density of mag 14 and brighter stars to be optimistically 1000/deg^2, from http://www.astronomycafe.net/qadir/q1257.html, that corresponds to a density of roughly 1e-4 stars per Gaia pixel, according to Gerald's numbers. So at any instant it's almost certain that there would be no stars close enough to a putative planet to be detectable with Gaia.
At 1000 AU, the object would have a period of roughly 32 000 yr, so would move roughly 360 deg/32 000 = 0.01 deg/yr in our sky. (Parallax would be of the same order or less.) This corresponds to roughly 40 Gaia pixels per year. So the object would sweep out an area with roughly 40*1e-4 stars per year, ie 4e-3 stars per year. So even accounting for the object's motion, we would not expect any stars bright enough and close enough to be detectable. We'd have to wait hundreds of years before a bright enough star happened to pass close enough.
So yes, this would be difficult, even if you knew exactly where the planet was!
Posted by: AJAW May 2 2016, 08:31 PM
Thanks for the info. The size of the gravitational lens is indeed small.
I have two questions:
Why are we talking about mag 14 stars? Gaia can go down to about mag 20.5, there ought to be a lot more of those stars.
Also, why twice the mass of the Earth? - I thought planet nine might be 10 times the mass of the Earth.
Posted by: fredk May 2 2016, 09:34 PM
According to the reference Gerald cited, at 20th mag the astrometric accuracy is 20 times worse than at 15th mag. So to see a lensing effect the star'd have to be 20 times closer to the planet, ie confined to an area roughly 400 times smaller, than for 15th mag stars. But we might expect only roughly a few hundred times as many stars down to 20th as down to 15th mag, so it doesn't help to push to fainter magnitudes, even when you consider the planet's motion. And pushing the planet's mass up 5 fold gets you out about 5 times farther, which still won't likely give you a star close enough.
Also the motion of a star due to variable deflection as the planet passes near by might just be degenerate with the star's proper motion. Ie, if you only observe for a short enough time how do you know if the star's position is being deflected by lensing, or the star just has a different proper motion? If you observe for long enough with enough samples, you could distinguish them in principle.
Posted by: AJAW May 2 2016, 10:03 PM
Thanks fredk. Pity about the accuracy change. One factor in our favour (but unlikely to be big enough) is that the sky areas most likely to contain planet nine are densely populated - a nuisance for
most searches but an advantage with this one.
If Gaia is aiming to get proper motions for all the stars it looks at (with 70 observations of each one) I guess we could distinguish that from the lensing effect, if there is any.
Posted by: TheAnt Jun 1 2016, 05:09 PM
Planet 9 might literally be out of this world.
A study by Univ of Lund, Sweden have shown that planet 9 (if it will be shown to exist) might have originated elsewhere, and been adopted by our solar system.
This is obviously one elegant way of explaining the remote and elongated orbit of this world, but also offer one opportunity to have a space probe visit an exoplanet in the not too distant future.
http://www.alphagalileo.org/ViewItem.aspx?ItemId=164652&CultureCode=en
Posted by: jasedm Jun 1 2016, 06:57 PM
No expert in celestial mechanics me, but my initial reaction is to think this is putting the cart before the horse - the planet has yet to be 'discovered' - it's posited from observational data of established Kuiper belt objects. A bit of a stretch therefore imho to infer an extra-solar origin of a body whose existence has not yet even been confirmed.
Happy to be shot down in flames for my opinion though.....
[MOD NOTE: THANK you!!!]
Posted by: JRehling Jun 1 2016, 08:27 PM
Planet Nine should perhaps be given the provisional name Phlogiston…
Posted by: JohnVV Jun 1 2016, 08:44 PM
or
plan 9 from planet 9
(been playing with " plan9 from bell labs" )
http://imgbox.com/xpsMxgI0
Posted by: HSchirmer Jun 1 2016, 11:29 PM
Happy to be shot down in flames for my opinion though.....
No, you are accurate.
"That isn't right, heck it isn't even wrong." Wolfgang Pauli
The youtube editing produces jumbled logic -
"there isn't enough material that far out to form an ice giant " (yes)
"so Planet 9 must have been captured at that distance from another star" (eh, no)
The video editing seems jumbled, it avoids the science questions: Where it did form? If if formed close to a star, then how did it get that far away in the first place?
Postulating that it formed around a different star simply displaces the question of how would it get from the snowline area to the outer fringe of a solar system.
That problem exists whether it formed around the sun, or around another nearby star.
Looking at the paper's abstract, things look a little better.
I think they are arguing that getting an ice giant from the inner solar system into an outer solar system elliptical orbit would disrupt the kuiper belt.
However, if the ice giant is captured from another star, it might stay far enough away to have an elliptical orbit without shredding the kuiper belt.
Posted by: TheAnt Jun 2 2016, 04:13 AM
At least I won't.
And also I am a bit hesitant on using the word 'evidence' as this thread got in the title.However, I still find this piece interesting that on condition it actually exists (that's why my parenthesis).
@JohnVV: Plan 9 from other space?
@HSchirmer: Yes that's how I understood it also. Though not being anywhere near an expert in celestial mechanic either, I found this possibility interesting enough to add a note about this. =)
And yes, Scott Sheppard and Chadwick Trujillo published a paper on a massive object shepherding inner Oort cloud objects in March 2014.
The press release from Carnegie then stated: "...their work indicates the potential presence of an enormous planet, perhaps up to 10 times the size of Earth, not yet seen, but possibly influencing the orbit of 2012 VP113, as well as other inner Oort cloud objects."
Posted by: nprev Jun 3 2016, 07:37 AM
All right, you guys....
Jasedm is exactly right, though. It's one thing to postulate a discovery like this based on analysis of the orbital parameters of other objects--it's been done before, of course--but this alleged planet now seems to have more authoritatively stated attributes than Neptune did before the discovery of Triton! (I'm sure there will be some article about postulated moons of this thing in short order...)
Posted by: scalbers Jun 3 2016, 06:21 PM
The exoplanet hypothesis is also discussed in the May 2016 issue of Scientific American. It seems like a reasonable idea keeping the appropriate caveats in mind. One note is that early in our solar system's history "we" could have been living in a star cluster and it would have been easier to borrow a planet.
Posted by: jasedm Jun 3 2016, 07:30 PM
Sorry, I didn't mean to set the cat amongst the pigeons.
Personally I'd be delighted if Planet IX is definitively confirmed in the near future - it would be another huge endorsement of the scientific method.
I'm reminded of the situation surrounding a postulated intra-Mercurial planet (Vulcan) in the latter part of the nineteenth century. It was proposed that a small planet might account for Mercury's orbital peculiarities, and several transits of the sun by a putative planet were observed by respected astronomers. As it turned out though, Einstein's theory accounted for the discrepancies, and it's unlikely that anything more than a few kilometres in diameter orbits closer to the sun than Mercury.
On the other hand, Neptune was 'discovered' mathematically so I'm not betting either way......
Posted by: Gerald Jun 14 2016, 02:56 PM
https://arxiv.org/abs/1603.05712 constrains its orbital parameter space, and the paper is honest about the possibility, that the existence of Planet Nine might eventually be ruled out, if new observations find KBOs inconsistent with the simulations. However, the simulations are still sparse, and might have overlooked some solutions.
One thing I'd wished for would have been explicite predictions about future observations of KBOs, in order to overcome the statistically somewhat questionable method of a-posteriori assessments of probabilities. This would open an option to provide statistically more rigorous indirect evidence for the existence of a Planet Nine. The crux with very eccentric planets is, that they are near their aphelion most of the time, where they are faintest.
Posted by: HSchirmer Jun 14 2016, 06:31 PM
Of course, any moon really ought to be named for 1950s sci-fi drive-in movies.
Malia, Nurmi, Vampirella, Ed, Wood...
Posted by: testguru Jul 12 2016, 07:52 PM
Will this new dwarf planet's [MOD: 2015 RR245] orbital elements help improve the predicted location of Planet X? Does it decrease the number of square degrees of sky as seen from earth that need to be searched? Does anyone have a star map of the current search area of sky that Planet X could be in?
Posted by: Explorer1 Jul 12 2016, 08:37 PM
Best place for Planet 9 info is the blog the paper co-authors wrote with a skymap.
http://www.findplanetnine.com/
So far nothing new about this latest object's implications for the search.
Posted by: Gerald Jul 12 2016, 08:57 PM
When looking at the graphics, my first impression is, that 2015 RR245 could have been scattered by Neptune, hence not directly related to the presumed Planet 9.
But it might inspire the possibility, that there might have existed a planet on a similar orbit as 2015 RR245, responsible for the clustering of objects attributed to a Planet 9.
It would be interesting to hear Mike Brown, whether he is assessing the new find as an increase or a decrease of the probability of the existence of a Planet 9. But I think that's hard to answer without prior simulations.
Posted by: alan Jul 13 2016, 05:19 PM
The objects influenced by Planet 9 are those with semimajor axes > 150 AU, particularly the detached objects with perihelion >42 AU. 2015 RR245's semimajor axis is 81 AU and its perihelion is 33 AU.
Posted by: Lucas Jul 14 2016, 11:28 AM
There's an article about this in today's New York Times with some interesting additional information from Drs. Bannister & Brown: http://www.nytimes.com/2016/07/14/science/astronomers-discover-new-likely-dwarf-planet.html
“I know that it’s going to fit in at least with most of the story,” Dr. Brown said. “It’s exactly in the direction it should be for Planet Nine.”
Posted by: alan Jul 14 2016, 06:47 PM
https://www.youtube.com/watch?v=_w9N6yABAW4&t=28m17s
Posted by: Mongo Jul 15 2016, 12:53 AM
http://arxiv.org/abs/1607.03963
Posted by: Mongo Sep 1 2016, 01:18 AM
http://arxiv.org/abs/1608.08772
Posted by: nprev Sep 1 2016, 05:01 AM
MOD NOTE: Just a reminder that in accordance with rule 1.9 please do not refer to this postulated object during discussion as "Planet 9" due to the ongoing (and indefinite, and definitely prohibited here) debate about what and what is not a planet.
Fully understand that external articles and authors do so constantly, but the Forum is not going to participate in or enable (even indirectly) this highly emotional, too often acrimonious, and frankly unscientific debate. Thanks!
Posted by: lilmac Sep 2 2016, 03:54 PM
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 https://en.wikipedia.org/wiki/Kozai_mechanism-like resonance with the observed population.
According to space-engine simulations, the Hill sphere could be several AU! Sounds plausible. It would be able to capture alot of stuff.
Posted by: alan Sep 2 2016, 08:06 PM
Odd gap in the perihelia:
Other surveys have found the other 19 known ETNOs, none of which have perihelion in the 50 AU to 75 AU range. If other surveys have similar biases to our own, the probability of this occurring by chance is roughly 0.29^19 = 6×10^−11 or about 7 σ assuming Gaussian statistics
Posted by: Mongo Sep 3 2016, 02:06 AM
There were a number of very interesting objects found, that were buried in the paper:
Posted by: HSchirmer Apr 3 2017, 01:49 PM
Crowdsourcing astronomy
https://www.zooniverse.org/projects/marckuchner/backyard-worlds-planet-9
60,000 volunteer astronomers sort through 4 million objects in 3 days,
they've identified 4 candidates for a large planet out in the kuiper belt.
A concentrated three-day search for a mysterious, unseen planet in the far reaches of our own solar system has yielded four possible candidates.
Posted by: JRehling Apr 6 2017, 03:55 AM
Interesting work. I would note that, if there is no more than one major distant planet, the false positive rate is, as a matter of logical necessity, either 75% or 100%, so interpret this preliminary work in that light. I think I'd title this work more cautiously with that extremely high false positive rate in mind. It's really not evidence of such a planet at all – it's a useful direction for future work.
Posted by: TheAnt Apr 8 2017, 12:25 PM
Indeed it's catchy headline, and that attract readers.
If we instead lift a sentence from the main text and use this as a headline:
"We’ve managed to rule out a planet about the size of Neptune being in about 90 per cent of the southern sky..."
The whole matter is turned on it's head.
But yes, interesting effort nevertheless.
Posted by: Holder of the Two Leashes Jun 23 2017, 02:22 PM
Now there is evidence of another fairly large body out there, this one around Mars mass and closer than 100 AU.
https://phys.org/news/2017-06-unseen-planetary-mass-warped-kuiper.html
It took a while, but I tracked down the paper on the LPL site:
https://www.lpl.arizona.edu/~renu/malhotra_preprints/kb-plane-2.pdf
Posted by: Holder of the Two Leashes Jul 13 2017, 02:20 PM
The latest ...
https://phys.org/news/2017-07-evidence-planet-hypothesis.html
Posted by: stevesliva Jul 25 2018, 09:15 PM
Given the discovery of more satellites of Jupiter as a result of the search for this planet, I decided to poke around for some news. Good long article here:
https://www.scientificamerican.com/article/looking-for-planet-nine-astronomers-gaze-into-the-abyss/
Posted by: stevesliva Mar 4 2019, 10:57 PM
Awhile ago I found this blog:
http://www.findplanetnine.com/
There are a number of recent updates from Konstantin Batygin.
Posted by: HSchirmer Mar 4 2019, 11:16 PM
http://www.findplanetnine.com/
There are a number of recent updates from Konstantin Batygin.
Interesting, our solar system seems to be missing a Super-Earth, guess that's where it got to.
Posted by: nprev Mar 5 2019, 04:16 AM
Reposting this as a reminder. Yes, I know that it is VERY difficult to do given the popular press coverage...but please make the effort.
I'll let the original posters make their own edits.
Fully understand that external articles and authors do so constantly, but the Forum is not going to participate in or enable (even indirectly) this highly emotional, too often acrimonious, and frankly unscientific debate. Thanks!
Posted by: stevesliva Mar 5 2019, 02:22 PM
It is hard, but the term also strikes me as a bit deliberately contentious, so I understand. I see someone got to my other post, which is good.
Posted by: Holder of the Two Leashes Jul 10 2020, 04:52 PM
It looks like a couple of astrophysicists at the University of Colorado Boulder are out to kill the giant outer planet hypothesis. And they may be succeeding.
Their computer simulations suggest that the KBOs whose orbits seemed to point that direction actually self assembled, along with the loss of a lot of mass.
LINK: https://www.sciencealert.com/things-are-real-weird-in-the-outer-solar-system-and-astronomers-are-homing-in-on-why
Posted by: stevesliva Mar 20 2024, 06:16 PM
New preprint on the (no luck) search so far:
https://www.universetoday.com/165774/theres-one-last-place-planet-9-could-be-hiding/
There was also a bunch of discussion here that tailed off in 2021:
https://findplanetnine.blogspot.com/
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