[HN Gopher] The Orbit of Planet Nine
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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.
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(page generated 2021-08-29 23:00 UTC)