"Aernus", A proposed new planet in the Kuiper Belt Options

[Greg Hullender]

At 100 AU, a several Earth mass object would be disqualified. This is a consequence of the zone clearing criteria which biases what is and is not a planet by distance

But the Kuiper Belt ends at 55 AU, right? Why wouldn't an Earth-sized object at 100 AU be a planet, provided it orbited in splendid isolation?

Now for a prediction: It shall fall before NH reaches Pluto.

I wouldn't be surprised if results from Pan-STARRS and/or LSST will force a radical rethink, and I note first light for LSST is scheduled for about the same time as N reaches Pluto.

But the real reason I posted here was to see a) if anyone has a link to the actual paper and how serious one ought to take it.

--Greg

[JRehling]

But the Kuiper Belt ends at 55 AU, right? Why wouldn't an Earth-sized object at 100 AU be a planet, provided it orbited in splendid isolation?

I guess the thought would be that that can't happen. For an Earth-sized object to be at 100 AU, the stuff for it to accrete out of has to be out there at about 100 AU. It couldn't have formed somewhere else and then made its way out there and just stopped unless there were something bigger out there. (A highly felicitous impact that significantly changed its orbit could do so, providing it didn't blast enough stuff off to once again reject the axiom.)

The period of an object at 100 AU is 1000 years. The volume of space around its orbit proportional to that of Earth is a million times as great. I'm certain the Earth hadn't cleared its orbit in 4.5 million years (the impacts on the Moon make that clear -- not by a long shot). So there's no reason to suspect that the "Early Heavy Bombardment" would even be over at that distance. Unless there wasn't enough stuff there for an Earth-sized object to accrete.

[Greg Hullender]

I guess the thought would be that that can't happen.

If that's the case, that's fine; I'm surprised we'd be that confident, though. Seems to depend a lot on assumptions about the original mass of the disk out there, plus the original composition. We can't already know everything or we wouldn't need to send NH out there! ;-)

Getting back to the paper (or the news article about the paper), it appears he's claiming this object is large enough to establish the outer edge of the Kuiper Belt -- just as Jupiter establishes (I think) the outer edge of the Asteroid Belt. Unless you take a rather disingenuous interpretation of "clearing the orbit" ("I want this orbit clean enough to EAT off of!") :-) then I'd say that anything that can limit the Kuiper Belt has really gone above and beyond the call of duty as far as orbit-cleaning goes.

Which gets back to my original question (which wasn't aimed at continuing the "is it a planet discussion"): Is Lykawka's hypothesis reasonable?

--Greg

[JRehling]

If that's the case, that's fine; I'm surprised we'd be that confident, though. Seems to depend a lot on assumptions about the original mass of the disk out there, plus the original composition. We can't already know everything or we wouldn't need to send NH out there! ;-)

Actually, my [non-professional] assessment doesn't depend on any assumptions about the original conditions. It handles all of them. Either there never was any stuff out there, or there was and it can't have ALL been consolidated into one body in so short a time. Even if the long orbital periods are the only difference between Earth and Earth-100AU that we take into account, it will have only made as many orbits as Earth made in its first 4.5 million years, which wasn't even close to long enough to clear our orbit. And that was with considerable help from Venus, Mars, and Jupiter. So basically, there has to be a vacuum OR clutter out there, and we don't know which, but we won't find a million cubic AU of clutter consolidated into one body in only 4.5 million orbits.

[Alan Stern]

I guess the thought would be that that can't happen. For an Earth-sized object to be at 100 AU, the stuff for it to accrete out of has to be out there at about 100 AU. It couldn't have formed somewhere else and then made its way out there and just stopped unless there were something bigger out there. (A highly felicitous impact that significantly changed its orbit could do so, providing it didn't blast enough stuff off to once again reject the axiom.)

The period of an object at 100 AU is 1000 years. The volume of space around its orbit proportional to that of Earth is a million times as great. I'm certain the Earth hadn't cleared its orbit in 4.5 million years (the impacts on the Moon make that clear -- not by a long shot). So there's no reason to suspect that the "Early Heavy Bombardment" would even be over at that distance. Unless there wasn't enough stuff there for an Earth-sized object to accrete.

..Simpler than that. The IAU definition is about whether the object *has* cleared its zone. At 100 AU, in fact, even at 30 AU, an object of Earth's mass cannot do the job in the age of the solar system. It's just physics. It can't. Therefore, in the IAU's view, an Earth mass object at 30, 50, 100, or farther out is not a planet. And with that absurdity alone (never mind the trash orbiting with planets, never mind Pluto crossing Neptune's orbit, never mind the "voting" by 4% of the IAU, etc etc.), the IAU planet definition fails the most basic test-the one that keep people from laughing at it.

-Alan

[dvandorn]

..Simpler than that. The IAU definition is about whether the object *has* cleared its zone. At 100 AU, in fact, even at 30 AU, an object of Earth's mass cannot do the job in the age of the solar system. It's just physics. It can't.

Glad I finished reading the thread before responding, 'cause that's the exact point I was going to make.

You have to remember, everybody, that the Kuiper Belt is a (likely spherical) shell of bodies, not the remains of the originally super-flat accretion disk. We're out past the disk, where accretion followed different rules, and may still be occurring.

That volume of space contains so many bodies in so many trajectories that don't cross each other for billions of years at a crack, that even a gas giant would have a hard time clearing it all out in the 4.5 billion years the Solar System has existed, much less an Earth-sized planet. It's simply a function of volume -- correct me if I'm wrong, someone, but doesn't the volume of the Kuiper Belt exceed the volume of the entire Solar System from Neptune on in? And unlike the "main" system, which occupies a pretty flat plane (thereby limiting its useful volume when discussing neighborhood-clearing), the more spherical nature of the Kuiper Belt increases the volume to be cleared -- well, literally astronomically.



-the other Doug

[ElkGroveDan]

Perhaps Kuiper "Belt" is an unfortunately deceptive term then. Possibly Kuiper "Shell" would have been a better choice of terminology.

[Greg Hullender]

At 100 AU, in fact, even at 30 AU, an object of Earth's mass cannot do the job in the age of the solar system. It's just physics. -Alan

Thanks, Alan; that's what I was wondering about. I wasn't something I could work out here at home with Excel and a paper notebook. :-)

dvandorn: Why do you say the Kuiper Belt is a shell? I have not heard that before. It's certainly not how it's depicted in the Hayden Planetarium as of last Saturday. :-) Are you sure you're not thinking of the Oort Cloud?

--Greg

[nprev]

Think he's onto something with that description, though, Greg.

At the very least, the Asteroid Belt is a relatively flat toroid due to solar tidal effects (in turn due to proximity to the Sun), which confines the majority of objects in the "traditional" Solar System to within just a few degrees of inclination with respect to the ecliptic.

I suspect that the Kuiper Belt planar distribution is at least tens of degrees above and below the ecliptic due to long, long orbital periods and much weaker tidal effects. It would be interesting to obtain rotation periods and axial inclinations for the larger KBOs. I suspect that many would not be tidally locked due to this, and fossil (because impact frequency has to be REALLY low compared to what we're used to down here by the fire) collision-induced rotation would dominate.

[alan]

My apologies if someone else has thought of this first and I didn't notice (or if it is impossible . . . )
IIRC, quite a few objects out Pluto way seem to be resonant with Neptune. (3:2 springs to mind)
Are any other solar orbital periods suspiciously common amongst the remainder of the other objects ??
Or any commensurabilities??

In the Kuiper belt there are a number of resonances occupied, the 2:3 two orbits per every three orbits of Neptune (plutinos) which you've mentioned, the 1:2 which appears to mark the outer border of the Kuiper belt, also there are objects in the 1:1 (Neptune Trojans) 1:3, 2:5, 3:4, 3:5, 4:5, and 4:7 resonances with Neptune see http://www.cfa.harvard.edu/mpec/K08/K08M16.html
With Jupiter there are the Trojans 1:1, and the Hildas 3:2.
With Mars there are 4 Mars Trojans and possible a significant number in the 1:2 resonance, see http://www.fisica.edu.uy/~gallardo/marte12/mars1to2.html

[Greg Hullender]

I suspect that the Kuiper Belt planar distribution is at least tens of degrees above and below the ecliptic . . .

Perhaps, but most found so far are within ten degrees of the ecliptic, based on what I found searching for "kuiper belt inclination". Lots of folks describe it as a torus (which is how the Hayden depicts it), but I haven't found a paper that described it as a sphere.

--Greg

[JRehling]

Perhaps, but most found so far are within ten degrees of the ecliptic, based on what I found searching for "kuiper belt inclination".

The catch is that surveys can be biased to look for bodies near the ecliptic (which will be the best use of telescope time if your aim is to maximize discoveries). So we really don't have good data yet. The following page complains that some surveys haven't even published their approach, so it's impossible to know how biased the searches thus far have been:

http://www.obs-besancon.fr/TNOdb/node3.html

[Greg Hullender]

If it's true that you maximize discoveries by looking for bodies near the ecliptic, then ipso facto the Kuiper Belt is not spherically distributed. Anyway, the catalog does show a handful of objects with highly inclined orbits, so it's not that no one is looking for them; they're just rare.

Back to the topic. Patryck has some nice diagrams of what he's talking about on his page:

http://harbor.scitec.kobe-u.ac.jp/~patryk/.../planet-en.html

I do wonder why his object has such an elliptical orbit though.

I found a no-subscription-required link to his last paper

http://xxx.tau.ac.il/ftp/arxiv/papers/0712/0712.2198.pdf

And I sent him an e-mail asking for a copy of the new one.

What's depressing is that a search for his name yields a huge number of psuedoscientific sites that try to cite his work as "proof" of their crazy ideas about how "Planet Nibiru" caused all the disasters in the Bible. Adding a "-nibiru" flag to a web search (minus in front of a term tells the search engine NOT to show pages with that word) cleans most of it up. This isn't Patryck's fault, of course, but it bothers me that I easily found pages and pages about the mythical Nibiru, but was unable to even learn the title of Patryck's new paper.

--Greg

[JRehling]

If it's true that you maximize discoveries by looking for bodies near the ecliptic, then ipso facto the Kuiper Belt is not spherically distributed. Anyway, the catalog does show a handful of objects with highly inclined orbits, so it's not that no one is looking for them; they're just rare.

Actually, it could be spherically distributed and the searches still be biased if the searchers BELIEVE that it's not. But the fact that more objects are in prograde orbits than retrograde indicates some degree of nonrandomization. However, the fact that some highly inclined orbits have been discovered does NOT mean that searchers are looking outside the ecliptic -- inclined orbits cross the ecliptic.

The larger point is that the orbits definitely deviate from the ecliptic, though not fully randomly. But we can't use the discovered objects to characterize the population because of a bias in the searches. The mean inclination observed so far can't be used as a measure of the actual mean inclination.

[Pavel]

Your task: Scour the fringes of the Solar System, and break up excessively large planets before they can pose a threat to astronomical law and order.

Also, you'll need to patrol neighborhoods of the established planets to make sure that they are cleared of any rogues.