[HN Gopher] The Orbit of Planet Nine ___________________________________________________________________ The Orbit of Planet Nine Author : fogof Score : 129 points Date : 2021-08-29 18:26 UTC (4 hours ago) (HTM) web link (findplanetnine.blogspot.com) (TXT) w3m dump (findplanetnine.blogspot.com) | ffhhj wrote: | What 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. | NiceWayToDoIT wrote: | How likely is that there are multiple smaller planets instead of | one 9th, on the same side working as offset? | Sharlin wrote: | They'd have different orbits with different orbital periods so | wouldn't stay "on the same side" over millions of years. | Hypx_ wrote: | > 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. | netcan wrote: | I 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 wrote: | The 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.htm... | | [1]: https://ai.googleblog.com/2019/08/turbo-improved-rainbow- | col... | petschge wrote: | Short 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 wrote: | The 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. | ttfkam wrote: | "...given that about 1 in 12 men have some form of colour | blindness?" | | I guess women are better suited to science work after all. ;) | vmception wrote: | > 6.2/+2.2/-1.3 Earth masses | | What is this telling me? | civilized wrote: | That 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 wrote: | Seems 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 | brysonreece wrote: | Planet Nine (supposedly) has a mass somewhere between 4.9-8.4x | that of our own planet. | kibwen wrote: | _> 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 wrote: | Either way, it would be very useful for inferring the | properties of extrasolar planets in that size range. | ximeng wrote: | https://en.m.wikipedia.org/wiki/Planet_Nine | OneEyedRobot wrote: | question: | | 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 wrote: | The oort cloud that is theorized to exist is hypothesized to be | up to several lightyears out. | | https://en.wikipedia.org/wiki/Oort_cloud | vmception wrote: | Do other systems have oort clouds or are their's also | something we cant see from this far | UnlockedSecrets wrote: | The 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. | OneEyedRobot wrote: | It 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. | nkrisc wrote: | > there's no hard definition. | | Yes. All human definitions are imperfect. | lumost wrote: | At 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. | Asraelite wrote: | This limit is called the 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. | dvh wrote: | What is the distribution (relative to galactic center) of TNOs | used for calculation? | njarboe wrote: | The 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 | mjevans wrote: | Sounds like a great start. Does this help us (as a species) | collect data in a more focused way to narrow the search? | azernik wrote: | Probably. It narrows down the range of locations and | therefore the search area. And given the potentially very low | brightness of the object, search area and hence telescope | time are limiting factors. | croutonwagon wrote: | Question. 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 wrote: | It could be, but it would be the size of a tennis ball. See | https://news.ycombinator.com/item?id=28167058 | lgl wrote: | > Could it be a small black hole? | | It could, the relevant part of the whole thing is the | object's mass (and therefore its gravitational influence) and | its orbit. | | Lex Fridman did a podcast interview a few months ago with | Konstantin Batygin [0] about the topic of Planet Nine and he | poses this exact question of whether or not it could be a | black hole [1]. | | More specifically, he asks if it could be a primordial black | hole which would make it a double discovery since primordial | black holes are still only theoretical. | | [0] https://www.youtube.com/watch?v=tm7poMupE8k | | [1] https://www.youtube.com/watch?v=tm7poMupE8k&t=4757s | 7373737373 wrote: | With a likely magnitude of ~21, it's seems out of reach for | amateur hunters | imglorp wrote: | What about watching for occultations of the stellar background | over time in the suspect area and using software to blink | compare? | 7373737373 wrote: | Reminds 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! | PicassoCTs wrote: | Wonder if you could take a NN and train it to deduce large body | pathways from physic simulations like | 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 wrote: | Yes, 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. ___________________________________________________________________ (page generated 2021-08-29 23:00 UTC)