They don't explain it in detail, but the reason it's consistent with Planet IX [1] is its orbit has specific properties that require a near pass with a large body in the outer solar system (basically the definition of Planet XI). That seems like it may be easy to do by other means, but if you've played Kerbal Space Program you know how difficult it can be to change all six orbital elements in the way you want to. For example, a close pass to Jupiter could launch something extremely far our, but it would not change it's perihelion or closest approach to the Sun. Like a Homann transfer, going to a larger orbit requires at least two "kicks": one to kick it into an ellipse and a second at the outer point. Planet XI would give the kick at a far distance to get many of these curious Trans-Neptunian Objects out to crazy perihelion distances like 65 au. There's also a specific effect to the inclination and argument of perihelion, but I don't understand how these work as well.
The amount of sky we have to look for Planet IX is enormous (and given how faint it is likely to be), and the evidence so consists of about ten of these TNOs with these orbits (not many, but it's very hard to make these orbits). But there are potentially hundreds of bodies with orbits like these waiting to be found by a the soon to be constructed LSST, which is an 8 meter telescope that will survey its entire sky every 3 days. With many more of these orbits to predict from, we may really narrow down the search space to look for it, and ultimately test its existence.
[1] Predicted by Konstantin Batygin and Mike Brown, the latter of which played a big part in helping to disqualify Pluto as a planet by discovering Eris. I know from a lunch-talk that he greatly relishs the thought of both demoting the former Planet XI and predicting the new one.
>> There's also a specific effect to the inclination and argument of perihelion.
To get a significant inclination (ie away from the low inclinations of the inner planets) and a drop in the perihelion (ie highly oval rather than the round orbits of the inner planets) you need a close pass of a large body. As the little think comes close to the big thing it is thrown randomly, away from the nicely round orbits of most things in the early solar system. So if you find a body with those two features, you know it passed close to something big somewhere our near the highest part of its orbit. That is the evidence of a large object out beyond pluto.
Yes, I agree, it's a combination of high inclination, perihelion, and eccentricity that point point to scattering.
The clustering of the arguments of perihelia is less straight forward (you can see it in Figure 4 of the linked pre-print PDF in another comment) and my limited understanding is that they are shepherded into that configuration over time by the large body. That is more clear when you see the results of the numerical simulations I suppose.
The number of potential encounters is also a factor. Objects in orbits this large, with periods measurable in thousands of years, won't have many periodic encounters. There isn't enough time since the formation of our solar system for them to get close enough together. The lower the number of potential encounters, the more significant must those be that do happen. That too points to a larger body out there.
So, just using a 1/r relation for potential energy, and the ratio of perhelion to aphelion, this thing has only ~3% of the potential energy at the outermost point in is orbit compared to the innermost point. That's practically miraculous on its own, isn't it?
The paper authors are actually arguing for a Planet X which has had periodic encounters much weaker than that at a distance of a few hundred au.
Quite the change in distance from the sun. Btw, kinetic energy is proportional to 1/r, and is at a peak at the perihelion. Potential energy is highest at the aphelion.
The diameter listed in the paper is 300km assuming a moderate albedo of 15%.
The paper suggested this object provides more evidence of the existence of Planet X/IX hypotheses of the authors (Trujillo/Shepard/et.al.) and Brown/Batygin.
Ceres considered a dwarf planed because it hasn't cleared the neighborhood around it's orbit, not because of it's size.
I don't think the suggestion is that this object is planet IX, it's that this object provides evidence that there may be some other planet IX out there.
I think that 'clearing its orbit' standard won't survive. Say we find an earth-sized object out there past pluto, or say a jupiter-sized object around another star, the fact that their orbits are full of other tiny objects won't matter. If it is big enough, the other technicalities will fall away.
A rogue planet orbiting a galactic core, or massive BH, would still be called a planet despite in no way clearing its orbit of anything.
If you trace the path of individual photons it seems implausible. That somehow a photon leaves the sun, travels possibly weeks until it strikes some nanoscopic face of a crystal on the surface of this object, which is rotating and travelling tangentially at several km/sec, and departs at such a resolved and precise an angle that it makes it almost all the way back to the sun, passes through the atmosphere of an orbiting body travelling 30km/sec, lands on a finely curated layer of aluminum where it is reflected yet again and lands on a square likely smaller than an index card.
I think that's a plain text way of saying "square centimetres" - `^` often means `xor` thus `^^` to mean exponentiation (and is less obtuse than `cm2`)
"You know, the most amazing thing happened to me tonight... I saw a car with the license plate ARW 357. Can you imagine? Of all the millions of license plates in the state, what was the chance that I would see that particular one tonight? Amazing!" —Richard Feynman
If you select a random point from [0, 1] segment, then probability of selecting that particular point is zero. Not "very close to zero", but "exactly zero".
Infinitesimals don't exist in standard analysis. There exist no positive numbers smaller than all positive real numbers. The probability of picking any given real number from [0, 1) is exactly zero, there's no other number it could be. Rigorously, the measure of any countable subset of real numbers is zero.
Honestly, I don't really "like" real numbers, exactly because they are defined as classes of equivalence of converging sequences of neighborhoods.
But I'm pretty sure even in rational numbers probability would be exactly zero, because that's how probability there is defined (as a limit of a sequence, and limit is zero).
The thing is 9 light hours out. It's 9 light hours back. What's the photon doing in the meantime? A little R&R on the beaches of Neptune, taking in the sights of floating diamonds?
Given that OP - our observer - is presumably on earth, it's a different reference frame. We'll still have to account for the difference of "possibly weeks" and and 18 hours.
And it's a really sorry state of affairs for photons that their vacations pass instantaneously.
(IOW: I was poking fun at the OPs statements of the photon travelling "possibly weeks", not making a statement of fact. I thought the "beaches of Neptune" bit gave it away, but I guess not)
That may or may not be accurate. The limit of time dilation function as velocity approaches speed of light is zero, but the function itself is discontinuous. It hits a division-by-zero.
I'm not smart enough to have that kind of doubt: you really got me thinking! And you made me think of the wave/particle duality. Detection over this distance seems much more plausible with the light-as-waves model; the waves behaving like er... waves and our detection of them working more like radar/echo-location.
It doesn’t make any difference - the probabilities would be the same. You can treat it as a bunch of photons (with the expected photon density that the sun emits) or as a light wave that collapses to a photon in the detector with probability given by the Born rule. The probability will work out the same.
That breaks my mental model of waves (which probably means my model needs improving). I imagined the probably of the wave reaching the detector was proportional to the energy of the original signal. Does that map directly to photons and probability? I suppose it must... woah.
Well since we still don't have any great explaination for the 200 year old double slit experiment, how do you know it is photons moving around? Could be star sized tsunami waves of light trashing about collapsing into photons when finally measured.
In fact, we do have an explanation for it - its called quantum theory and it explains and predicts not only the double slit experiment but many other much more complicated phenomena.
Meh. Predicts, yes. But I expect you could poll massive support for the proposition "the standard model is an accurate description of what happens, but not an explanation of why things would be like that".
>Well since we still don't have any great explaination for the 200 year old double slit experiment
I'm duty-bound to point out that this is only true in a philosophical, interpretive sense based on the aesthetics of explanations. Scientifically it's completely understood.
We can only predict the outcome of the double-slit experiment. We do not know how that outcome comes to be, nor do we know "why" the rules are the rules.
I think you are asking for answers beyond what science can offer. Our current understanding of mathematics and logic suggest that every scientific theory will always have some axioms that we will have to take on "faith". Moreover, contrary to popular belief, science is process of eliminating the false theories leaving behind a set of _possibly true_ theories. Our current understanding of the philosophy of science suggests that we will never be able to infer the "true" laws of the universe. How can you answer the "why" if you don't even know if the current physical laws are the "true" ones.
Science is just a way of compressing what we perceive with our senses into compact descriptions that our easy to memorize and understand by human beings. That is all. In the words of Neil Bohr, "Physics is to be regarded not so much as the study of something a priori given, but rather as the development of methods of ordering and surveying human experience.".
>Our current understanding of mathematics and logic suggest that every scientific theory will always have some axioms that we will have to take on "faith".
I don't think this is true. The axioms can be testable, in which case you can do a little better than faith and say that "well, this is how it seems to work." For example I could have a theory that when I press the gas pedal my car moves forwards. Later on I could discover another theory that explains why that theory is true, but in the meantime I'm better than faith but worse than complete fundamental knowledge. That's where physics is - if we had complete fundamental knowledge many of us would go home, having nothing left to do.
That's even cooler, photons popping into existence like whitecaps on a wave as the energy coalesces to a point after travelling independently for hundreds of billions of miles.
As a matter of fact we do have, and it's quite understandable by anyone with an understanding of high-school physics if you can spare a few (<10) hours to study.
Yeah, I have no intuition with this. The telescope they used was 8.2m and they used 300-400 second exposures (with spectral filters). I guess it comes down to space being really really dark and cyrogenically-cooled CCDs having pretty good noise floors.
The authors had this to say about it:
Surprisingly, like 2012 VP113, 2015 TG387 is relatively bright compared to the limiting magnitude of most of the survey fields. The Subaru observations generally go deeper than 25.5 mags, making 2015 TG387 about 1.5 mags brighter than the limiting magnitude of the disocovery survey fields it was found in.
The estimated rate of dust accumulation on the Moon is around 15cm/billion years. So the footprints and other traces would disappear at some point between 10 and 100 million years.
It's really hard to estimate how long the hardware might last. Obviously there's no air or water, but there will be damage from radiation, temperature cycling, and micrometeorite abrasion.
A wild guess would be a similar timescale - max 100 million years, at which point there will be small anomalous piles of metal dust left, but no visible structure.
That would make a great episode of Star Trek - finding a planet like Earth, with a moon, and no sign of life on the planet or any visible structures of any kind. But their moon has tracks and vehicles.
That's because they don't believe this stuff for rational reasons but to fit into a group or in some cases as a "fuck you belief" directed at "the establishment."
"Fuck you beliefs" are a personal theory of mine. People sometimes assume ridiculous and deliberately provocative "beliefs" as a means of explicit rejection of a social order. The canonical example would be Satanism as a rejection of Christian culture/society. Believing Apollo is a hoax or that the Earth is flat is an explicit rejection of the industrial/scientific/corporate/university complex and its culture. The absurdity of these beliefs adds to their value as acts of protest. The phenomenon can also take the form of refusal to believe something taught by the hated authority. If the belief being refused is actually true and demonstrably so, it becomes a more potent act of protest.
Talk to the people that hold beliefs like the Apollo hoax and scratch the surface and you'll usually find someone who is under-employed in a dead-end job with no future and too much student loan debt. They are adopting an absurdist epistemology in protest of a society that they see as having failed them.
When I see conspiracy theories becoming popular I see a metaphysical and epistemological version of people throwing Molotov cocktails in the street at cops in riot gear under clouds of tear gas. Maybe this is what mass protests and "riots in the street" look like in the Information Age.
Adaptive optics [0] takes care of atmospheric distortions. Combined with the huge telescopes that are possible on earth and impossible to ferry to space in the foreseeable future, advancements in sensors and data processing, which is also much, much easier on earth and at best possible with constraints / a long delay in space, I think earth based telescopes are still the future.
Special cases like the infrared spectrum (JWT) exist. But the delays show how extremely difficult space based observation is.
"Active optics is not to be confused with adaptive optics, which operates at a shorter timescale and corrects atmospheric distortions." ~ "Active optics", Wikipedia
Because it's small and exists in darkness in the outer realms. Also, it's just great marketing. Who the hell wouldn't want to read about a goblin planet? Made me click on the link.
I also wondered if it was representative of a class of Goblin objects. I guess the discoverers just liked 'goblin' as a term for something that stays in the dark.
It has nothing to do with borderline clickbait - I know people sure didn't click on this link for the faint hope of a fanciful world of hunched over creatures shuffling around doing Goblin things. So yeah, now that we know that definitely isn't the case, it should help to narrow it down
I gather from this article that its orbital radius varies between 65 AU and 2300 AU, which is an extremely eccentric ellipse. I wonder if that high eccentricity would disqualify it from "planet" status. Most other bodies considered "planets" are far closer to circular.
It's also unclear to me if the Goblin orbits in the usual planetary plane.
Probably the simple fact that it does not clear its orbit disqualifies it from planet status. And it's probably too small to be in hydrostatic equilibrium (not enough self-gravity to force it to a roundish shape).
Out of interest: I looked up "Hydrostatic equilibrium" and it says "[thing is in equilibrium] when the flow velocity at each point is constant over time". How exactly does that statement relate to what you said?
Most objects in space have some amount of spin to them. That is particles throughout a body, each with a velocity that may be changing, but the change in velocity with position is smooth, or the object would be ripping itself apart. This means the object has flow. A noticeably misshapen object will not have relatively constant speed and angular direction as a function of latitude and radius. However, objects that gravity rounds out do have this feature (to within an approximation, there is still weather). Thus the term hydrostatic equilibrium. The reason we don't just say "circular" is that this does not include oblate objects, which result from higher spin.
It took some additional help from IRC but I think I got it now. Thanks for your answer!
In general, while total angular momentum is conserved, rigid bodies tend to rotate in an unstable fashion, because rigid-body forces apply different amounts of torque to different parts of the object. Which I kind of knew about but I didn't connect the dots.
Hence no constant speed and angular direction, and no hydrostatic equilibrium. That was the missing link for me!
So, flow velocity is simply the fluid mechanical velocity vector field/mapping. And it has to be constant, otherwise the object would not be in equilibrium, but it'd be still flowing (as in it would have parts that are going somewhere).
Now I think this definition you have found is not directly applicable to rotating celestial bodies, as the point velocity is a vector, and it constantly changes due to the rotation.
So probably a higher order derivative is zero, and that's the condition that we should use.
Or of course we can transform to a non rotating frame.
But what the parent poster said confuses me: "a velocity that may be changing, but the change in velocity with position is smooth, or the object would be ripping itself apart. This means the object has flow." You can have smooth and constant rotation but with many axes (tumbling), so I don't really see how this gets us to roundisness.
As I understand the concept, the point is that "the object doesn't have parts that want to fall toward its center of gravity, but can't because rigid forces", because it's big enough that gravity creates enough pressure and heat that everything becomes plastic over thousands of years, and thus flows. (But this doesn't make much sense, because cold enough rock is pretty stable - as far as I know - so the material will only allow gravity to overcome it if it undergoes enough crystal structure faults [due to radioactive decay or exogenous damage, such as micrometeorites] - so the flow rate is constant, zero, even if there are stresses and forces that would increase the flow.)
You have a few misconceptions and you are waaaaay overthinking this. The primary measure for this equilibrium is the time derivative of the mass-density-velocity, or momentum-density if you like. Now imagine a cube spinning on a primary axis. Since a cube is not constant radius, there are times where matter exists at a given point and other times where the matter does not exist at that point. Clearly, the time derivative of the momentum-density is not zero. This is not the case for a sphere as any point that has mass under the spinning sphere will have mass at all later points in time. The reason we don't just say sphere, though, is this kind of equilibrium accounts for oblate objects as well, and many planets are oblate.
> A proposal before the International Astronomical Union for the definition of a planet would have defined a planet as "a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet"[2].
Quoted above[0], "Inclination of 11.669 degrees" (from the preprint) would indicate it has greater inclination than the 8 planets, but less than some other small distant bodies[1].
Slowly we're getting closer to proving another planet is out there. I do like it when nutters spewing out 100's of mad theories a month get one correct, in this case its the existence of Nibiru.
The fun thing is that Planet X/Nibiru/Nemesis are basically crazy talk (but different from each other), and Planet IX is quite possibly true, but also distinct from the foregoing.
But they are all synonymous in internet conspiracy land, (and in their eyes, corroborate each other's existence).
The paper this article refers to actually refers to 'Planet X' as the theorized large planet in its section on orbital stability models.
I think the planet X moniker originally meant 'x' as unknown (it was coined during the search that found Pluto). Nowadays, it has been used to refer to several distinct theories including Planet IX. I dunno when exactly the X got re-interpreted.
What I do know is WE'RE DOOOOMED! (according to the internet).
The amount of sky we have to look for Planet IX is enormous (and given how faint it is likely to be), and the evidence so consists of about ten of these TNOs with these orbits (not many, but it's very hard to make these orbits). But there are potentially hundreds of bodies with orbits like these waiting to be found by a the soon to be constructed LSST, which is an 8 meter telescope that will survey its entire sky every 3 days. With many more of these orbits to predict from, we may really narrow down the search space to look for it, and ultimately test its existence.
[1] Predicted by Konstantin Batygin and Mike Brown, the latter of which played a big part in helping to disqualify Pluto as a planet by discovering Eris. I know from a lunch-talk that he greatly relishs the thought of both demoting the former Planet XI and predicting the new one.