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The Orbit of Planet Nine
- Hypx_ 5y ago> Put these two plots together and you get a 99.6% chance that the objects are clustered, rather than uniform. That sounds pretty good to me. That's not even three-sigma. I'm not sure if this is real evidence of a planet nine. Just a chance alignment of orbits seem like the most plausible explanation.
- ncmncm 5y agoThree sigma is pretty damn good for something like this. It means it's not worth sending a probe out yet, but is more than enough justification for serious telescope time.
- aaron695 5y agoYes, but because of the bias, which is talked about, they need to get it higher. This really need to be commented on by the writers of earlier papers showing the bias in the early data. It won't be outright chance that caused this.
- ximeng 5y agohttps://en.m.wikipedia.org/wiki/Planet_Nine https://en.m.wikipedia.org/wiki/Planet_Nine
- OneEyedRobot 5y agoquestion: How far out can a planet be if it has a roughly circular orbit? At some point outwards neighboring heavy things will make it unstable.
- UnlockedSecrets 5y agoThe oort cloud that is theorized to exist is hypothesized to be up to several lightyears out. https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud
- OneEyedRobot 5y agoIt seems to me that something that's a couple of lightyears out can't have any sort of stable orbit. I suppose that an Oort cloud essentially merges with an adjacent star's so there's no hard definition.
- lumost 5y agoAt the point of merger with neighboring stars it’s likely that circular orbits are unstable. Judging by our own solar system it’s likely that the distance at which circular orbits are stable is a question of relative mass, and time.
- nkrisc 5y ago> there's no hard definition. Yes. All human definitions are imperfect.
- vmception 5y agoDo other systems have oort clouds or are their’s also something we cant see from this far
- UnlockedSecrets 5y agoThe only physical evidence we have they exist are comets that occasionally show up in the inner solar system where we could observe them which have orbits that are not interstellar but would put them as going incredibly far out. From that we can extrapolate that they likely exist around every star but there is no way we could verify that with our current technology since any light reflected off the objects would be far too faint to detect.
- dehrmann 5y ago> https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud The distances between the planets fit nicely on a log scale.
- Asraelite 5y agoThis limit is called the Hill Sphere: https://en.wikipedia.org/wiki/Hill_sphere https://en.wikipedia.org/wiki/Hill_sphere For the Sun it's a bit more than 1 light year, but in practice almost all orbits will be quite a bit under this: less than 0.8 ly.
- koheripbal 5y agoThe Hill Sphere also changes over time as stars pass us. The galaxy is more of a soup - the stars in the neighborhood don't have a static position to one another. ...so I would imagine that anything even 1ly out would be unstable, over several hundred million years. Solar systems may even exchange very outer outer "planets".
- dvh 5y agoWhat is the distribution (relative to galactic center) of TNOs used for calculation?
- netcan 5y agoI love the way this is written. It's like the author, as a scientist, is in the service of humanity. The tone, language, the tongue in cheek apology... Something very noble and approachable to it. Good job. Find that planet for us! We appreciate it.
- murphyslab 5y agoThe writing is great, but I keep wondering: Why do so many physicists use Jet or other non-perceptually uniform rainbow-like colourmaps for their graphs? Shouldn't that be part of great science communication, given that about 1 in 12 men have some form of colour blindness? There are so many other visually appealing options [0] that are attractive while still being perceptually uniform. There's even Google's Turbo [1] colourmap for those who refuse to give up rainbow-like colourmaps. [0]: https://matplotlib.org/stable/tutorials/colors/colormaps.html https://matplotlib.org/stable/tutorials/colors/colormaps.htm... [1]: https://ai.googleblog.com/2019/08/turbo-improved-rainbow-colormap-for.html https://ai.googleblog.com/2019/08/turbo-improved-rainbow-col...
- petschge 5y agoShort answer: because none of them is the default in standard plotting tool. There is so many alternative that it is hard to know which replacement you should pick. If you pick the wrong one you are a moron, if you stick with the bad default it's way less noticeable, even if it is a strictly worse choice.
- murphyslab 5y agoThe default issue is certainly keenly felt. My first scientific publication graphs were done with Jet. But since switching to some of the perceptually uniform ones (most often Viridis), I've never had a complaint. But your point "if you stick with the bad it's way less noticeable" is understandable.
- maxnoe 5y agoMatplotlib 2.0 came out in January 2017 and has a perceptually uniform, colorblond friendly colormap as default and three others available. There is no exclude for using Jet today and Journals should reject papers using bad colormaps
- njarboe 5y agoThe abstract from the paper[1] linked to from the article is a good read and short, so I think it is worth quoting here: "The existence of a giant planet beyond Neptune -- referred to as Planet Nine (P9) -- has been inferred from the clustering of longitude of perihelion and pole position of distant eccentric Kuiper belt objects (KBOs). After updating calculations of observational biases, we find that the clustering remains significant at the 99.6\% confidence level. We thus use these observations to determine orbital elements of P9. A suite of numerical simulations shows that the orbital distribution of the distant KBOs is strongly influenced by the mass and orbital elements of P9 and thus can be used to infer these parameters. Combining the biases with these numerical simulations, we calculate likelihood values for discrete set of P9 parameters, which we then use as input into a Gaussian Process emulator that allows a likelihood computation for arbitrary values of all parameters. We use this emulator in a Markov Chain Monte Carlo analysis to estimate parameters of P9. We find a P9 mass of 6.2 (+2.2, −1.3) Earth masses, semimajor axis of 380 (+140,−80) AU, inclination of 16±5∘ and perihelion of 300+85−60 AU. Using samples of the orbital elements and estimates of the radius and albedo of such a planet, we calculate the probability distribution function of the on-sky position of Planet Nine and of its brightness. For many reasonable assumptions, Planet Nine is closer and brighter than initially expected, though the probability distribution includes a long tail to larger distances, and uncertainties in the radius and albedo of Planet Nine could yield fainter objects." [1] https://arxiv.org/abs/2108.09868 https://arxiv.org/abs/2108.09868
- croutonwagon 5y agoQuestion. Does it have to be a planet out there? Could it be a small black hole? Or is it just a matter of us not spending the time/effort to find it. I know time on instruments like Hubble is very, very tight and scheduled out years in Advance. But they have been talking about Planet X since like the 80s at least, and probably earlier. Even Pluto was detectable relatively early and it’s on a crazy orbital plane and elliptical orbit.
- solidangle 5y agoIt could be, but it would be the size of a tennis ball. See https://news.ycombinator.com/item?id=28167058 https://news.ycombinator.com/item?id=28167058
- 7373737373 5y agoWith a likely magnitude of ~21, it's seems out of reach for amateur hunters
- imglorp 5y agoWhat about watching for occultations of the stellar background over time in the suspect area and using software to blink compare?
- 7373737373 5y agoReminds me of a documentary (which I can't find anymore) about New Horizons and the hunt for Ultima Thule, where the scientists did the exact same thing!
- koheripbal 5y agoVery very unlikely. Relative to the Earth, P9 and background stars don't move much at all relative to one another.
- PicassoCTs 5y agoWonder if you could take a NN and train it to deduce large body pathways from physic simulations like https://universesandbox.com/ https://universesandbox.com/. Then pump the known history of the solar system in and find out with what it fills the gap. Probably not due to nine being such a outlier, would have to arrange the model to not filter out rare events.
- robbedpeter 5y agoYes, and modern methods would be really easy to incorporate because of awesome open source libraries. If you got really lucky, there could be public data from telescopes that had already recorded whatever regions of space were of interest, and evidence of planet nine might have been disregarded as noise.
- bdamm 5y agoIs this something NNs could do? The output might just be a probability field of orbits, which would not tell you anything more than known analytical methods would.
- biofox 5y agoPeople are being conditioned to apply NNs to every problem, regardless of their suitability. Having to only think about a single tool makes everything easier.
- gbrown 5y agoI mean, based just on the abstract that's not entirely unlike what they're doing, except that they're using GP emulation.
- vmception 5y ago> 6.2/+2.2/-1.3 Earth masses What is this telling me?
- civilized 5y agoThat looks like an asymmetric error bar, meaning the best estimate is 6.2 but could be 2.2 above or 1.3 below. Essentially it's a common physical scientist way of expressing a point estimate with a confidence interval. (In the life and social sciences they tend to just provide the point estimate and confidence interval explicitly.)
- legobmw99 5y agoSeems like an uneven error interval? Meaning if it’s not our estimated valid of 6.2, we have less confidence in the upper bound than the lower bound, or our estimates are distributed nonuniformly
- hoseja 5y agoWhich makes sense since physical quantities like this can't be negative and so can't be normally distributed.
- brysonreece 5y agoPlanet Nine (supposedly) has a mass somewhere between 4.9-8.4x that of our own planet.
- NiceWayToDoIT 5y agoHow likely is that there are multiple smaller planets instead of one 9th, on the same side working as offset?
- Sharlin 5y agoThey’d have different orbits with different orbital periods so wouldn’t stay “on the same side” over millions of years.
- ncmncm 5y agoUnless they were a double-planet, similar to Pluto/Charon. (Those orbit a common center not inside either body.) To my knowledge, they are unique, in that, among known bodies, though it would not be surprising if there were a few tiny double asteroids.
- raxxorrax 5y agoSince we are talking about ~350AU (Pluto is at ~40AU), that may very well be the case. An easy approximation: https://www.sjsu.edu/faculty/watkins/bode.htm https://www.sjsu.edu/faculty/watkins/bode.htm
- koheripbal 5y agoGiven how far out they are, how far off the solar system axis, and how small, it's definitely possible that there are multiple objects.
- ffhhj 5y agoWhat if it's a planet temporarily captured by our solar system which is currently deataching due to an unstable orbit? Moons are temporary, why not planets, even suns.
- fallingknife 5y agoOrbits don't just detach. Even at the predicted aphelion distance of 460 AU, P9 would have an orbital velocity of 1.4 km/s and a solar escape velocity of 2 km/s. So to detach from solar orbit you would need a minimum delta-v of 600 m/s. 600 m/s on a planet size object is only going to happen if a star happens to wander through the solar system.
- koheripbal 5y agoIt's possibly a transient object - ie not in orbit around the sun, but just passing through. For all we know it formed billions of years ago in another system, and then was ejected from its home system from some near miss with its sister gas giant.
- fallingknife 5y agoMy understanding was that it had to be in orbit for a long time to cause the observed pattern, but you could be right.
- kibwen 5y ago> We find a P9 mass of 6.2 (+2.2, −1.3) Earth masses This wouldn't even be half the mass of the smallest gaseous planet, but would be much larger than the largest terrestrial planet. Which do astronomers think it would be?
- azernik 5y agoEither way, it would be very useful for inferring the properties of extrasolar planets in that size range.
- ncmncm 5y agoSince it would be frozen, it would be hard to call it a gaseous planet. Even water, nitrogen, and oxygen are rocks, out there.
- koheripbal 5y agoIt would be rocky.
- SideburnsOfDoom 5y agoIt would be of a temperature where most things are rocks. If it's not Hydrogen, it's rocks.
- cratermoon 5y agoPretty sure the orbit of Pluto has been well-known for some time now.
- danwills 5y agoSay there is a planet out there, might it have a protective effect from things hitting earth, similar to how Jupiter is said to help reduce the chances of things hitting earth? Maybe it's too far away, but multi-body dynamics is complicated! Considering the previous lizard 'lords' of-the-earth for millions of years seem to have been largely ended by such a collision, maybe there's more we should be doing to detect and prepare for such an event?
- habibur 5y agoFor comparison : Pluto is 40 AU from sun, against P9's 400 AU. 10 times further. And 6 times mass of earth. Where Uranus and Neptune are x15 of earth. Inclination 6 degrees are comparable with other planets.
- koheripbal 5y agoAh... that will make it very hard to detect even with the largest telescopes, unless we have some specific coordinates. Makes you wonder if maybe the interstellar space is just filled with tons of these little rocky planets.
- yamaneko 5y agoVeritasium did a video about Planet 9 [1] with one of the authors of this article, Konstantin Batygin. It also features David Jewitt with opposing arguments regarding the existence of Planet 9. [1]: https://youtu.be/pe83T9hISoY https://youtu.be/pe83T9hISoY
- prideout 5y agoIt sounds like the opposing arguments are: (1) if you want something to exist, you'll be biased in your observations, (2) we might simply be unaware of a bunch of Kuiper objects, and those unknown objects might be exerting their influence, and (3) we haven't actually seen P9 yet, visually, so skepticism is healthy until then.
- yamaneko 5y agoYes, thank you. It's been a while since I've watched the video, so calling it "opposing arguments" was a stretch. More like a healthy dose of skepticism.
- fractallyte 5y agoSeems like a perfect test for the Titius-Bode-Blagg law (https://en.wikipedia.org/wiki/Titius%E2%80%93Bode_law https://en.wikipedia.org/wiki/Titius%E2%80%93Bode_law). (No, not the original Bode's Law, which was just a first approximation! Mathematician Mary Blagg did the real work in the early 20th century, but was mostly unacknowledged until nearly 70 years later.) It works, not just for the solar system, but also for the satellite systems of Jupiter and Saturn; but no one knows precisely why...
- SideburnsOfDoom 5y agoDo they give the odds of the null hypothesis? i.e. that there is no planetary mass object out there.