The Orbit of Planet Nine

https://findplanetnine.blogspot.com/2021/08/the-orbit-of-planet-nine.html

by fogof • 5 years ago

259 82 5 years ago

findplanetnine.blogspot.com

Hypx_• 5 years 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.

ncmncm5• 5 years ago

Three 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.

ximeng• 5 years ago

https://en.m.wikipedia.org/wiki/Planet_Nine

OneEyedRobot2• 5 years ago

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.

UnlockedSecrets2• 5 years ago

The oort cloud that is theorized to exist is hypothesized to be up to several lightyears out.

https://en.wikipedia.org/wiki/Oort_cloud

OneEyedRobot2• 5 years ago

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.

vmception2• 5 years ago

Do other systems have oort clouds or are their’s also something we cant see from this far

dehrmann• 5 years ago

https://en.wikipedia.org/wiki/Oort_cloud

The distances between the planets fit nicely on a log scale.

Asraelite• 5 years ago

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.

koheripbal8• 5 years ago

The 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• 5 years ago

What is the distribution (relative to galactic center) of TNOs used for calculation?

netcan• 5 years ago

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.

murphyslab2• 5 years ago

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• 5 years ago

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.

ttfkam• 5 years ago

"...given that about 1 in 12 men have some form of colour blindness?"

I guess women are better suited to science work after all. ;)

geokon4• 5 years ago

This feels overengineered...

Since it's showing a probability density, wouldn't it make most sense to just use a grayscale in this case? As the probability density approaches zero the visual would disappear as well. This is more intuitive, as the probability is zero off the edge of the graph/page

I think you only need this color vomit if you have a change between two states, or you have multiple intermediary states and want some visual "clustering".

You can actually see the problem very clearly b/c it ends up having a weird dark-blue to white cut is some of the plots.

njarboe• 5 years ago

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

croutonwagon• 5 years ago

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• 5 years ago

It could be, but it would be the size of a tennis ball. See https://news.ycombinator.com/item?id=28167058

lgl• 5 years ago

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

NL807• 5 years ago

Counter argument against the black hole hypothesis includes the lack of powerful x-ray activity where the black hole should be. Also, its size would be quite unusual, which in that case could be a primordial black hole, which in itself is theoretical and never been observed.

nxpnsv• 5 years ago

Could yes. But it certainly is not the easiest explanation.

ncmncm5• 5 years ago

If it were a black hole, which would necessarily mean a primordial black hole, we would never spot it. We would look, and look, and eventually give up and say it must be a statistical fluke. A coal-black body would also be hard to spot. Surprisingly many asteroids are black, for poorly-understood reasons.

mjevans• 5 years ago

Sounds like a great start. Does this help us (as a species) collect data in a more focused way to narrow the search?

azernik3• 5 years ago

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.

mc32• 5 years ago

In Cartoons (and in science), wasn't this called Planet X and in other hypothesis 'Nemesis'?

I get that Pluto was demoted, but it's still a planet, if dwarfish, so it should still be Planet X (X as in ten, but X can also mean undetermined number, which is perfect).

dragonwriter• 5 years ago

In Cartoons (and in science), wasn't this called Planet X and in other hypothesis 'Nemesis'?

Nemesis is a hypothetical star, not Planet 9/X, explaining different phenomena; it would be farther out.

But, yes, Planet 9 is more recent name for the same hypothetical object as Planet X:

https://solarsystem.nasa.gov/planets/hypothetical-planet-x/i...

73737373732• 5 years ago

With a likely magnitude of ~21, it's seems out of reach for amateur hunters

imglorp• 5 years ago

What about watching for occultations of the stellar background over time in the suspect area and using software to blink compare?

73737373732• 5 years ago

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!

koheripbal8• 5 years ago

Very very unlikely.

Relative to the Earth, P9 and background stars don't move much at all relative to one another.

PicassoCTs• 5 years ago

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• 5 years ago

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.

bdamm• 5 years ago

Is 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• 5 years ago

People 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• 5 years ago

I mean, based just on the abstract that's not entirely unlike what they're doing, except that they're using GP emulation.

vmception2• 5 years ago

6.2/+2.2/-1.3 Earth masses

What is this telling me?

civilized• 5 years ago

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• 5 years ago

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

hoseja3• 5 years ago

Which makes sense since physical quantities like this can't be negative and so can't be normally distributed.

brysonreece• 5 years ago

Planet Nine (supposedly) has a mass somewhere between 4.9-8.4x that of our own planet.

NiceWayToDoIT• 5 years ago

How likely is that there are multiple smaller planets instead of one 9th, on the same side working as offset?

Sharlin• 5 years ago

They’d have different orbits with different orbital periods so wouldn’t stay “on the same side” over millions of years.

ncmncm5• 5 years ago

Unless 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• 5 years ago

Since 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

koheripbal8• 5 years ago

Given 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• 5 years ago

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.

fallingknife2• 5 years ago

Orbits 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.

koheripbal8• 5 years ago

It'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.

kibwen• 5 years 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?

azernik3• 5 years ago

Either way, it would be very useful for inferring the properties of extrasolar planets in that size range.

ncmncm5• 5 years ago

Since it would be frozen, it would be hard to call it a gaseous planet. Even water, nitrogen, and oxygen are rocks, out there.

koheripbal8• 5 years ago

It would be rocky.

SideburnsOfDoom2• 5 years ago

It would be of a temperature where most things are rocks.

If it's not Hydrogen, it's rocks.

habibur• 5 years ago

For 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.

koheripbal8• 5 years ago

Ah... 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.

yamaneko2• 5 years ago

Veritasium 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

prideout• 5 years ago

It 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.

yamaneko2• 5 years ago

Yes, 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.

cratermoon• 5 years ago

Pretty sure the orbit of Pluto has been well-known for some time now.

danwills• 5 years ago

Say 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?

fractallyte• 5 years ago

Seems like a perfect test for the Titius-Bode-Blagg 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...

SideburnsOfDoom2• 5 years ago

Do they give the odds of the null hypothesis? i.e. that there is no planetary mass object out there.

The Orbit of Planet Nine

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