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
----------

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.

The lack of innovation has been discussed and largely rebutted here:

http://www.unmannedspaceflight.com/index.php?showtopic=7842

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?

MOD NOTE: Let's please stay on topic.

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?

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

For visual magnitude 14 stars, GAIA should see displacements of about 10 micro arcseconds (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 gravitational deflection angle, 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 a FOV of 0.66° and 1966 pixels, 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.

Taking the number density of mag 14 and brighter stars to be optimistically 1000/deg^2, from here, 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!

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.

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.

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.

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.
"Theft behind planet 9 in our solar system."

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!!!]

Planet Nine should perhaps be given the provisional name Phlogiston…

or
plan 9 from planet 9
(been playing with " plan9 from bell labs" )

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.

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."

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...)

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.

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......

The most recent paper of Mike Brown et al. about the search for a Planet Nine 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.

Of course, any moon really ought to be named for 1950s sci-fi drive-in movies.

Malia, Nurmi, Vampirella, Ed, Wood...

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?

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.

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.

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.

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/...arf-planet.html

SETI talk by Michelle Bannister where that one is discussed

Solar Obliquity Induced by Planet Nine

New Extreme Trans-Neptunian Objects: Towards a Super-Earth in the Outer Solar System

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!

According to space-engine simulations, the Hill sphere could be several AU! Sounds plausible. It would be able to capture alot of stuff.

Odd gap in the perihelia:

There were a number of very interesting objects found, that were buried in the paper:

Crowdsourcing astronomy
https://www.zooniverse.org/projects/marckuc...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.

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.

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.

Now there is evidence of another fairly large body out there, this one around Mars mass and closer than 100 AU.

Warped Kuiper disk

It took a while, but I tracked down the paper on the LPL site:

Draft Version

The latest ...

New evidence in support of the {Trans-Neptunian Gas Giant} hypothesis

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/...into-the-abyss/

Awhile ago I found this blog:
http://www.findplanetnine.com/

There are a number of recent updates from Konstantin Batygin.