Planet X found?

[-Sentinel-]

Some astronomers speculate there may be a sizeable trans-Neptunian planet in the Kuiper Belt (http://www.nature.com/news/evidence-grows-for-giant-planet-on-fringes-of-solar-system-1.19182), over 200 astronomical units from the Sun. They have not observed it directly, but can infer its existence from its gravitational effets on other Kuiper Belt objects. If it does exist, it has an exceptionally long period (10,000-20,000 years), even compared to known outer planets.

Claims of "Planet X found!" have been made and debunked many times in the past, so we'd best approach this sort of news cautiously.

http://chainsawsuit.com/wp-content/uploads/2016/01/20160120_pluto.png

[Flickerdart]

I like the idea that all these perturbations are caused by one or more rogue planets that aren't orbiting any star but just zooming through space on their own accord.

[factotum]

Really? So where have all these rogue planets come from, Flickerdart? There must be absolutely millions of them flying around for even one to come close enough to perturb Kuiper belt objects. (As an example, the stated nearest approach of Planet X, 200 AU, is only a bit more than one light-day from the Sun, which is less than a thousandth of the distance to the nearest other star--the chances of some random planet wandering into such a tiny (in astronomical terms) space is remote.

I personally think it would be *more* interesting to have an unknown planet orbiting out that far away. How would it have ended up in such a distant and highly elliptical orbit? Some sort of massive impact with another body in the early stages of Solar System formation?

[warty goblin]

I'm holding out hope that the planet's core serves as the secret base for a pair of hardened space pirates, from which they strike out against the sinister purple cephalopod empire of Planet W. He's tough and lean as weathered wood, she's hard and sharp as a steel blade, they're a pair of wolves in a world made for sheep. The Patrol's got a 100,000 Credit bounty on the pair of them, but haven't got a hope of catching the Star Witch, their stolen and illegally modified Briggs-Forscythe Pattern XII rocketship.

[Emperordaniel]

I personally think it would be *more* interesting to have an unknown planet orbiting out that far away. How would it have ended up in such a distant and highly elliptical orbit? Some sort of massive impact with another body in the early stages of Solar System formation?

I think the running theory is that it is/would have been a proto-giant of the ice or gas type, but was ejected by Jupiter before it managed to grow too large.

[KillianHawkeye]

Really? So where have all these rogue planets come from, Flickerdart? There must be absolutely millions of them flying around for even one to come close enough to perturb Kuiper belt objects.

That is... ... not how probability works! :smallsigh:

[halfeye]

Apparently, astronomers have searched and not found a planet of Saturn's size or more, out to quite far into the Oort.

Which is sad, because it would be lovely to have a Jupiter mass dwarf planet.

[Emperordaniel]

Which is sad, because it would be lovely to have a Jupiter mass dwarf planet.

"Jupiter mass" and "dwarf planet" are not words that go together. :smalltongue:

[erikun]

Some astronomers speculate there may be a sizeable trans-Neptunian planet in the Kuiper Belt (http://www.nature.com/news/evidence-grows-for-giant-planet-on-fringes-of-solar-system-1.19182), over 200 astronomical units from the Sun. They have not observed it directly, but can infer its existence from its gravitational effets on other Kuiper Belt objects. If it does exist, it has an exceptionally long period (10,000-20,000 years), even compared to known outer planets.

Claims of "Planet X found!" have been made and debunked many times in the past, so we'd best approach this sort of news cautiously.

http://chainsawsuit.com/wp-content/uploads/2016/01/20160120_pluto.png
Such a shame. We could've had Planet X be the 10th planet in the solar system, but NOOOOO.....
:smalltongue:

As an aside, Pluto's Dad is Cronus/Kronos (https://en.wikipedia.org/wiki/Cronus), and descended of Uranus.

[halfeye]

"Jupiter mass" and "dwarf planet" are not words that go together. :smalltongue:
You might think that, but the Oort is very big, and it takes a long time for something to make a complete circuit of the sun out there.

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


A dwarf planet is a planetary-mass object that is neither a planet nor a natural satellite. That is, it is in direct orbit of the Sun, and is massive enough for its gravity to crush itself into a hydrostatic equilibrium shape (usually a spheroid), but has not cleared the neighborhood of other material around its orbit.

The silly third of the definition is "has not cleared the neighborhood of other material around its orbit.", and given the periods of orbits out in the Oort, that's almost certainly the case for anything that far out that's of less than stellar mass.

There could have been a saner definition, but they were in a hurry to call Pluto a dwarf before they had to call half a dozen others planets, so they went with something silly.

[Emperordaniel]

You might think that, but the Oort is very big, and it takes a long time for something to make a complete circuit of the sun out there.

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



The silly third of the definition is "has not cleared the neighborhood of other material around its orbit.", and given the periods of orbits out in the Oort, that's almost certainly the case for anything that far out that's of less than stellar mass.

There could have been a saner definition, but they were in a hurry to call Pluto a dwarf before they had to call half a dozen others planets, so they went with something silly.

Long time, yes. Multi-hundred-million-year orbits? I... doubt that. The solar system is billions of years old, which is plenty of time for any Jupiter-sized body to have "cleared its orbit" - a phrase which is defined as being gravitationally dominant in its orbital zone, not "having emptied its orbital zone of all other bodies". Jupiter itself has around 6,000 known Trojan asteroids which roughly share its orbit (to say nothing of all the comets it influences), and every planet from Venus to Neptune - with the notable exception of Saturn - possesses at least one Trojan; plus, there are tens of thousands of asteroids and short-period comets which make close approaches to every planet from Mercury to Neptune. However, the eight true planets are still gravitationally dominant in their orbits - that is, there's nothing close to any of them which is both of a similar size and is not under the effect of the planet's own gravity.

Pluto, being located in the Kuiper belt, is surrounded by objects of relatively similar size which its own gravity is too weak to affect - it hasn't cleared its orbit of rival Kuiper belt objects. Hence, the dwarf planet designation.

[Talion]

We must alert Duck Dodgers! (https://en.wikipedia.org/wiki/Duck_Dodgers_in_the_24%C2%BDth_Century)! We must have that Illudium Phosdex! How else will we ever stabilize our dangerously low shaving cream reserves?

[factotum]

That is... ... not how probability works! :smallsigh:

OK, so how about you tell me *how* my argument is wrong rather than just saying "LOL you is wrong, N00b"?

[Swordsmith]

Planet IX maybe. For planet X, we need to find a second!

[hamishspence]

As an aside, Pluto's Dad is Cronus/Kronos (https://en.wikipedia.org/wiki/Cronus), and descended of Uranus.

Which, as is pointed out there - was "Saturn" to the Romans.

If Planet IX does get confirmed, then, to keep the theme - it'll need a Roman name - and one that hasn't been used already for an asteroid.

[Emperordaniel]

Uranus has a Greek name, so that would broaden our options somewhat - which is good, because I don't see there being a lot of Greco-Roman names left that haven't been chosen for something yet. :smalltongue:

[hamishspence]

Uranus has a Greek name, so that would broaden our options somewhat - which is good, because I don't see there being a lot of Greco-Roman names left that haven't been chosen for something yet. :smalltongue:

True - the Roman equivalent was apparently Caelus:

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

[RCgothic]

Well I think 'Ix' is a perfectly suitable name. :smallwink:

[Killer Angel]

I like to think it's a Starkiller Base.

[RCgothic]

This inspired me to look up the history of the search for trans-uranic planets, and one thing I noted was that at the time, Planet X would have been the ninth planet (before the discovery of Pluto before it's demotion)! The X just stands for unknown.

This could still be planet X!

[Flickerdart]

Really? So where have all these rogue planets come from, Flickerdart?
We just need one, which happened to fly by. But it's way more interesting if there are loads of them because rogue planets can theoretically still harbor life (http://www.wired.com/2011/02/steppenwolf-planet/). They could move slowly enough that we can hop from planet to planet to get to other star systems, rather than be lost in an endless void forever.

[Sith_Happens]

OK, so how about you tell me *how* my argument is wrong rather than just saying "LOL you is wrong, N00b"?

By definition the difference between an unlikely event and an impossible one is that the unlikely event will eventually happen.

[DigoDragon]

I am excited to find out if that is our missing 'Planet X (http://www.bbc.com/news/science-environment-35365323)'. Maybe our next 'New Horizons' probe could be designed to check it out? Course it would take a decade to get out there so... gotta be patient.

[factotum]

By definition the difference between an unlikely event and an impossible one is that the unlikely event will eventually happen.

But there were several bodies perturbed into different orbits by the passage of something, so we'd be talking multiple rogue planets, hence my scepticism. One orbiting planet making multiple passes seems a more likely explanation.

[Flickerdart]

One orbiting planet making multiple passes seems a more likely explanation.

I never said anything about likelihood. I simply think that it would be super-cool to have rogue planets zipping by, compared to an orbiting one that we already have tons of.

[Closet_Skeleton]

If Planet X can be 'found' by "inferred its existence from the way several other Kuiper belt objects (KBOs) move" then it was 'found' in the mid 19th century as well when its existence was 'inferred' from planetary motions.

When there's no difference between 'evidence that doesn't fit our calculations which we know aren't exact anyway' and 'evidence for an invisible planet' then all speculation sounds kind of pointless.

[Emperordaniel]

I am excited to find out if that is our missing 'Planet X (http://www.bbc.com/news/science-environment-35365323)'. Maybe our next 'New Horizons' probe could be designed to check it out? Course it would take a decade to get out there so... gotta be patient.

Hmm. Hypothetically, if this planet has a decently-sized atmosphere and is as massive as we're expecting (so we're talking a super-Earth or mini-Neptune with a mass up to 10x that of Earth), we might actually be able to get a probe into orbit within a relatively reasonable timeframe through a combination of aerobraking and Oberth maneuvering. New Horizons was moving at 13.78 km/s when it reached Pluto around 30-ish AU away from the Sun, so I'd assume that a probe sent to this planet - which could be as much as 20x the distance from Earth to Pluto - would be traveling a lot slower than that by the time it reached the planet.

EDIT: Wait, 20x the distance to Pluto? Scratch that, there's no way we're getting there in my lifetime. :smallfrown:

[Binks]

If Planet X can be 'found' by "inferred its existence from the way several other Kuiper belt objects (KBOs) move" then it was 'found' in the mid 19th century as well when its existence was 'inferred' from planetary motions.

When there's no difference between 'evidence that doesn't fit our calculations which we know aren't exact anyway' and 'evidence for an invisible planet' then all speculation sounds kind of pointless.
That was pretty much my reaction to this news as well. There's been evidence of a planet past Pluto since before we found Pluto after all. And even if this is a new one it's very vague evidence (a handful of KBO's are moving in a similar orbit out of the tens of thousands we suspect are out there) to go on. Not to mention that the assumption it's 1 single giant planet in the Kuiper Belt causing the observed disturbances is kind of a logical leap.

I mean, I'm all for drumming up interest in astronomy whenever possible, but this isn't really much of a discovery. If they actually find Planet X then it'll be meaningful, but the 'there's another planet out past Pluto!' train has been running for over a century at this point without finding anything. Kind of has a boy who cried wolf feel to it by now for me at least.

[Bobbybobby99]

EDIT: Wait, 20x the distance to Pluto? Scratch that, there's no way we're getting there in my lifetime. :smallfrown:

Don't fret! Unless possibly if you're in your eighties or similar, we shall develop faster probes! And have developed faster probes! And are continuing to do so all the time!

[Lord Torath]

Here's Phil Plait's in-depth explanation and analysis of Planet 9.
Slate: Bad Astronomy (http://www.slate.com/blogs/bad_astronomy/2016/01/21/evidence_found_of_a_possible_planet_in_the_outer_s olar_system.html).

He goes into detail of how the proposed Planet 9 orbit could have affected the orbits of the other Kuiper-Belt objects, like Sedna.

[Emperordaniel]

Here's another image, showing the orbits of the most distantly-orbiting non-cometary bodies around the Sun (including Sedna; surprisingly enough, Sedna isn't even close to being the most distantly-orbiting non-cometary body) - note the large gap on the right, which is where Planet Nine is predicted to be:
https://upload.wikimedia.org/wikipedia/commons/9/94/Celestia_distant_object_orbits.png

And here's a much-zoomed-in image showing only a handful of orbits (of which Sedna is the most distant), but which marks the predicted orbit for Planet Nine:
http://2.bp.blogspot.com/-0s4cVuBPocA/Vp7ehQGo-wI/AAAAAAAAAW4/78Y2V1o9AWg/s1600/P9_KBO_orbits_labeled.jpg

Note that this region is huge enough that even in the zoomed-in version, Pluto's orbit - a region we took nearly a decade to reach using the fastest probe ever launched - is barely visible (here's an image just showing Sedna's orbit next to the outer solar system for scale):
https://upload.wikimedia.org/wikipedia/commons/e/e3/Sedna_orbit.svg

[weaseldust]

If Planet X can be 'found' by "inferred its existence from the way several other Kuiper belt objects (KBOs) move" then it was 'found' in the mid 19th century as well when its existence was 'inferred' from planetary motions.

When there's no difference between 'evidence that doesn't fit our calculations which we know aren't exact anyway' and 'evidence for an invisible planet' then all speculation sounds kind of pointless.

I can understand thinking it hasn't been found yet, since even if it exists we don't know its location, but surely this counts as evidence for its existence? Suppose someone actually located the planet tomorrow on exactly the kind of orbit this team predicts it should have. Would you really say "OK, you found it, but you didn't have any evidence for it"?

I also think it's fair to say the existence of this planet might have been discovered by this team even if it hasn't been found. A body can be discovered by its effect on other bodies - that's how we know about the Milky Way's central black hole, for instance. And if this new planet exists, it wasn't discovered by anyone prior to this team because it's central to the identity of this planet (if it exists) that it explains the orbits of the specific bodies that have just been used to predict its existence. For instance, suppose I predicted a ninth planet a year ago based on some feature of the orbit of Neptune that this new planet couldn't possibly cause. Would you really say I had discovered this new planet, even though it bears no relation to my prediction?

[DigoDragon]

EDIT: Wait, 20x the distance to Pluto? Scratch that, there's no way we're getting there in my lifetime. :smallfrown:

Don't fret! Unless possibly if you're in your eighties or similar, we shall develop faster probes! And have developed faster probes! And are continuing to do so all the time!

NASA recently succeeded in testing an Electro-Magnetic Drive (http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/) within a lab environment. They want to build a prototype to put into space. May or may not be ready in our lifetime, but possible the next generation will see a round trip to Mars possible in half the time it takes currently.

[Eldan]

Obviously, wie must name it Yuggoth.

[Emperordaniel]

NASA recently succeeded in testing an Electro-Magnetic Drive (http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/) within a lab environment. They want to build a prototype to put into space. May or may not be ready in our lifetime, but possible the next generation will see a round trip to Mars possible in half the time it takes currently.

That sounds like the sort of thing you'd need a ton of power for; in other words, not something you could use past Jupiter/Saturn with current solar panel technology, maybe Uranus if you want to go all-out and give the space probe ISS-plus-sized solar panels. Planet Nine has a projected apoapsis of around 1,200 astronomical units (around 40x the 30-ish AU distance from the Sun to Pluto when New Horizons encountered it - at that distance, the amount of sunlight you're getting is already equivalent to post-sunset dusk) and a semi-major axis of 700 astronomical units; at those distances the Sun is little more than an abnormally bright star, which means you'll have to rely on some other form of power, and consequently a propulsion system that doesn't need a whole lot of it, seeing as you'll need to power all the other stuff the space probe has as well. If EM drives ever really catch on - and that's a big IF - I don't see them as being used for anything more than inner solar system transit, I'm afraid. :smallfrown:

Speaking of names for the planet, I rather like the name Nox (after the Roman god of night), seeing as from the planet's PoV, there'd be little visible difference between the day side and night side - both sides would be shrouded in darkness due to its distance.

[DigoDragon]

That sounds like the sort of thing you'd need a ton of power for; in other words, not something you could use past Jupiter/Saturn with current solar panel technology

Ideally they want to build a nuclear reactor to power it.

[Peelee]

It should clearly be named after my kitten - Erebus, Primordial Deity of Darkness.

[BannedInSchool]

Where are we going? Planet Ten! When? Real Soon!

[Emperordaniel]

It should clearly be named after my kitten - Erebus, Primordial Deity of Darkness.

Oooh, that's even better - we already have the asteroid Nyx and the moon Nix, so Nox may be a bit too similar; on the other hand, a quick search doesn't turn up any solar system body by that name, so it'd be relatively unique. Plus, the whole primordial deity thing would fit well with this planet being hypothesized to be left over from the early stages of solar system formation.

[Chronos]

Quoth DigoDragon:

NASA recently succeeded in testing an Electro-Magnetic Drive...

Quoth Emperordaniel:

That sounds like the sort of thing you'd need a ton of power for
Quite the contrary: If that thing actually works, we'll be able to use it to make perpetual motion machines, as it defies conservation laws. Which is a fancy way of saying that it almost certainly doesn't work, and that the results NASA is seeing are due to some sort of experimental error. Really, they're not trying to figure out how to scale it up or anything like that; they're trying to figure out what their experimental error is.

On the question of what gets to be called a planet, I think that it's silly to consider Pluto to be in the same category as Earth or Jupiter... but then, I also think it's silly to consider Earth and Jupiter to be in the same category. Really, we ought to have three separate categories: Rockballs, consisting of Mercury, Venus, Earth, Luna, Mars, and Ceres; gasballs, consisting of Jupiter, Saturn, Uranus, and Neptune; and iceballs, consisting of Eris, Pluto, Quaoar, Sedna, and a bunch of others. It remains to be seen whether this new object (if it even exists) is a rockball or gasball (or even an iceball, though I doubt iceballs can get that big).

[Bobbybobby99]

Quite the contrary: If that thing actually works, we'll be able to use it to make perpetual motion machines, as it defies conservation laws.

Really? My knowledge of physics is hazy, at best (I'm mostly ignoring the field because it's the sort of thing where what you learn in school today is irrelevant by the time you're mature in hears), but would defying the law of conservation of momentum, really let you produce free energy? Perhaps I'm just not thinking hard enough...

[halfeye]

On the question of what gets to be called a planet, I think that it's silly to consider Pluto to be in the same category as Earth or Jupiter... but then, I also think it's silly to consider Earth and Jupiter to be in the same category. Really, we ought to have three separate categories: Rockballs, consisting of Mercury, Venus, Earth, Luna, Mars, and Ceres; gasballs, consisting of Jupiter, Saturn, Uranus, and Neptune; and iceballs, consisting of Eris, Pluto, Quaoar, Sedna, and a bunch of others. It remains to be seen whether this new object (if it even exists) is a rockball or gasball (or even an iceball, though I doubt iceballs can get that big).
I quite agree. I have only a very slight wish Pluto wasn't demoted, but the way it was done was IMHO silly. However, Ceres is almost certainly an iceball like Pluto. The giants also fall into two groups, the gas giants Jupiter and Saturn, and the ice giants Uranus and Neptune.


Long time, yes. Multi-hundred-million-year orbits? I... doubt that. The solar system is billions of years old, which is plenty of time for any Jupiter-sized body to have "cleared its orbit" - a phrase which is defined as being gravitationally dominant in its orbital zone, not "having emptied its orbital zone of all other bodies". Jupiter itself has around 6,000 known Trojan asteroids which roughly share its orbit (to say nothing of all the comets it influences), and every planet from Venus to Neptune - with the notable exception of Saturn - possesses at least one Trojan; plus, there are tens of thousands of asteroids and short-period comets which make close approaches to every planet from Mercury to Neptune. However, the eight true planets are still gravitationally dominant in their orbits - that is, there's nothing close to any of them which is both of a similar size and is not under the effect of the planet's own gravity.

Well, I did mention the Oort, where I believe a more or less circular orbit would be millions of years long, and where anything with less than stellar mass in an approximately circular orbit would not have cleared its orbit. This object, if it exists, may be a Kuiper belt object in an extremely eliptical orbit, the other orbits do look very lopsided which if there are no orbits that are being ignored does suggest that there's something happening in that region.

The main reason for wanting there to be a Jupiter mass dwarf planet is that it would be hilarious, but the rules as they stand make the mass of a planet less important to its planethood than how far out from its star the perihelion of its orbit is, which is IMO very silly.


Pluto, being located in the Kuiper belt, is surrounded by objects of relatively similar size which its own gravity is too weak to affect - it hasn't cleared its orbit of rival Kuiper belt objects. Hence, the dwarf planet designation.

They should have gone with mass, and accepted that Mercury and Mars might have been due to go too, and as Chronos says bunged the giants in yet another mass class.

[Chen]

Really? My knowledge of physics is hazy, at best (I'm mostly ignoring the field because it's the sort of thing where what you learn in school today is irrelevant by the time you're mature in hears), but would defying the law of conservation of momentum, really let you produce free energy? Perhaps I'm just not thinking hard enough...

That EM drive thing is almost certainly not a perpetual motion machine. The experiments are not complete and the extremely minor thrust that was produced was almost certainly due to some other factor. I'm pretty sure there was a thread about this somewhere on this forum a couple months ago.

[Emperordaniel]

Well, I did mention the Oort, where I believe a more or less circular orbit would be millions of years long, and where anything with less than stellar mass in an approximately circular orbit would not have cleared its orbit. This object, if it exists, may be a Kuiper belt object in an extremely eliptical orbit, the other orbits do look very lopsided which if there are no orbits that are being ignored does suggest that there's something happening in that region.

The main reason for wanting there to be a Jupiter mass dwarf planet is that it would be hilarious, but the rules as they stand make the mass of a planet less important to its planethood than how far out from its star the perihelion of its orbit is, which is IMO very silly.

Planetary mass is important, though - it's how the planets dominate their orbits in the first place. Also, AFAIK, there is no current model for a Jupiter-sized object even being able to form that far out from its star; of all the planetary-mass objects we've discovered in any solar system so far (including our own), the one with the longest orbital period - extrasolar planet GU Piscium b (https://en.wikipedia.org/wiki/GU_Piscium_b) - only takes 163,000 years to go around its star, a lot less than the multi-million year orbit you're proposing for a Jupiter-sized body. And even if, hypothetically, there was a planet with a multi-million year orbit through the Oort cloud, its mass would by definition automatically let it dominate its orbit, seeing as there would be nothing else in its vicinity that would remotely be able to compete with it.

I might be completely wrong in my understanding of this, but the way I see it, the further out a planet's location, the easier it is to dominate its orbit, seeing as it would have less competition from other bodies.

[Binks]

I can understand thinking it hasn't been found yet, since even if it exists we don't know its location, but surely this counts as evidence for its existence?
The problem is that this isn't the first bit of evidence for this sort of thing. We're, what, 1 for 4* on actually finding planets in the solar system by spotting anomalies in other planet's orbits? Yeah, if they find this one, this will be evidence for it, but I wouldn't bet on it given the past performance of these sorts of theories...

*
Actually Found:
*Neptune (The only planet I'm aware of we found via this method)

Predicted this way but not actually there:
* Vulcan (predicted to explain Mercury's orbit under Newtonian gravity, disproven by Einstein)
* Lowell's original Planet X (predicted to explain oddities in Uranus/Neptune's orbits, disproven by Voyager 2)
* Tyche (predicted to explain the bias for long period comets, disproven by 2014 WISE survey)

Not to mention the theories about Nemesis, or the other Planet X candidate theories that have come and gone to little fanfare.

[Eldan]

It should clearly be named after my kitten - Erebus, Primordial Deity of Darkness.

Good choice there, you actually found something Grecoroman that doesn't have something named after it yet, which is rare. There's just a crater on Mars.

[halfeye]

Planetary mass is important, though - it's how the planets dominate their orbits in the first place. Also, AFAIK, there is no current model for a Jupiter-sized object even being able to form that far out from its star; of all the planetary-mass objects we've discovered in any solar system so far (including our own), the one with the longest orbital period - extrasolar planet GU Piscium b (https://en.wikipedia.org/wiki/GU_Piscium_b) - only takes 163,000 years to go around its star, a lot less than the multi-million year orbit you're proposing for a Jupiter-sized body. And even if, hypothetically, there was a planet with a multi-million year orbit through the Oort cloud, its mass would by definition automatically let it dominate its orbit, seeing as there would be nothing else in its vicinity that would remotely be able to compete with it.

How about if there were two at about the same distance from the sun? That's very improbable I believe, but if there were, how could either of them dominate? Or do they have to merge/collide?


I might be completely wrong in my understanding of this, but the way I see it, the further out a planet's location, the easier it is to dominate its orbit, seeing as it would have less competition from other bodies.

We don't know that there would be less competition, there is supposed to be a lot of stuff in the Oort, more distantantly spaced out but moving at what seems to us like random.

Further/higher orbits are higher energy, an object will be travelling faster in a higher orbit, but not moving so many degrees relative to it's primary.

Since an objects gravitational effect is a function of its closeness to another object, the further out an object is orbiting the less of it's orbit it will be dominating at any one time. I would guess as a first approximation that the amount of space dominated would be about the same in a given unit of time, so if an orbit of 10,000 years might be just minimally dominated by an object of some size, an object of the same size in a more distant orbit while still dominating 10,000 years of its orbit (which would be slightly longer, because the speed would be higher because of the higher energy), would not be dominating the whole of it, because the orbit took longer than 10,000 years, I'm not at all sure that time dominated thing is exactly right, but if feels as if it might be in the right sort of order of magnitudes.

[Peelee]

Oooh, that's even better - we already have the asteroid Nyx and the moon Nix, so Nox may be a bit too similar; on the other hand, a quick search doesn't turn up any solar system body by that name, so it'd be relatively unique. Plus, the whole primordial deity thing would fit well with this planet being hypothesized to be left over from the early stages of solar system formation.
Man, I didn't even realize that last part. I was just half-joking/half-suggesting because of the whole "darkness/ we can't see it" thing going on. That seriously is a damn good name.

Good choice there, you actually found something Grecoroman that doesn't have something named after it yet, which is rare. There's just a crater on Mars.
....and a kitten in Alabama.

[Closet_Skeleton]

I can understand thinking it hasn't been found yet, since even if it exists we don't know its location, but surely this counts as evidence for its existence? Suppose someone actually located the planet tomorrow on exactly the kind of orbit this team predicts it should have. Would you really say "OK, you found it, but you didn't have any evidence for it"?

Evidence isn't proof. They've only predicted the existence of a planet X. Of course it it does get found those who predicted it will be able to pat themselves on the back. Just like how all the previous predictors don't get to because their predictions turned out to be wrong.


There are a few ways to get orbits to align like this, but the most likely given what’s seen is—you guessed it—the presence of a massive planet out beyond Neptune. They've even nicknamed it: Planet Nine. The idea is that the objects started out with random orbits, but repeated close encounters with this purported planet nudged them into paths that all had similar characteristics.

So yeah, its just the most likely of several theories (which just means its the theory that best fits with other theories we like that be themselves might be wrong). With the nebula hypothesis slowly collapsing1 nobody even knows how planets are formed or why they should have the random orbits we were expecting and didn't find.

There's plenty of evidence for the Loch Ness Monster and alien abduction but that doesn't make either of those real.


that's how we know about the Milky Way's central black hole, for instance.

That's why the dominant cosmological paradigm infers the existence of a central black hole. No Black hole has ever been proven to exist on the level that planets in our solar system have been. The standards for confirmation are just so completely different once you leave the solar system. Black holes rest on a chain of assumptions and inferences while planets are much easier to empirically verify.


Obviously, wie must name it Yuggoth.

Pluto is already Yuggoth.


Quite the contrary: If that thing actually works, we'll be able to use it to make perpetual motion machines, as it defies conservation laws.

The whole claim that it violates conservation of energy came from people who were trying to disprove that it works. Nobody who actually supported the idea made that claim. Instead they claimed that the EM cavity drive used quantum vacuum energy to conform to conservation of momentum laws and most physicists said "quantum vacuum energy does not work that way".

Conservation of momentum only really applies to rocket propulsion. Helicopters don't care about it2, but don't work in space so nobody is complaining. EM cavity drives still haven't actually been tested in space, only in artificial vacuum chambers on earth where the supposed drive was attached to the wall of the chamber.


I quite agree. I have only a very slight wish Pluto wasn't demoted, but the way it was done was IMHO silly. However, Ceres is almost certainly an iceball like Pluto.

Pluto isn't an iceball, New Horizons kind of blasted that idea flat (its got a lot of ice in it though).

1aka "we'll revise it a little and hope the band aids don't stick out too much"

2only joking, of course they technically care about it, but not in the same direct way rockets do

[weaseldust]

Evidence isn't proof. They've only predicted the existence of a planet X. Of course it it does get found those who predicted it will be able to pat themselves on the back. Just like how all the previous predictors don't get to because their predictions turned out to be wrong.

Who said anything about proof? My point is just that it should be valued like similar scientific work, like our approach to detecting black holes, rather than like mere speculation.


On the subject of whether the hypothetical ninth planet could clear its orbit, this paper (http://www.boulder.swri.edu/~hal/PDF/planet_def.pdf) (PDF) introducing the concept says it is about identifying "large bodies that architecturally shape the system".

It also introduces a parameter (big lambda) that characterises the differences between planets and dwarf planets, but I can't work out what units they're using so I can't calculate it for our hypothetical ninth planet. (I think they're using solar masses for the mass unit and AU/Earth years for the SMA/period, but I can't replicate all their calculations that way. Maybe I'm missing something obvious.)

That said, even if the ninth planet exists and hasn't cleared its orbit yet because there are still some bodies that have avoided being captured or forced into resonances, unless there's some other planet out there competing with it, it is going to be the most significant force in determining the orbits of other bodies in that region. After all, the evidence for its existence is that it has seemingly forced multiple, distant, large-ish bodies into certain orbits, which is something Pluto can't do because it is competing for influence with the much bigger Neptune. So it will be more akin to actual planets than dwarf planets in its capacity to shape the solar system, even if the actual shaping effect it has is diminished due to the length of its orbit. On that basis, I'd say classifying it as a planet would make more sense than classifying it as a dwarf planet.

[Emperordaniel]

How about if there were two at about the same distance from the sun? That's very improbable I believe, but if there were, how could either of them dominate? Or do they have to merge/collide?The only way that scenario sounds even remotely stable to me is if they were formed in each other's L4 or L5 Lagrangian points (https://en.wikipedia.org/wiki/Lagrangian_point); otherwise, one or both of them would either migrate, collide with each other, or get ejected from the system within a relatively short timescale. However, even if they did form in the L4 or L5 region, that wouldn't necessarily provide for a stable system - the leading theory for how the Moon was formed does posit a collision between Earth and a Mars-sized body which originally formed in the L4/L5 region, after all - and although I'll admit we haven't been finding extrasolar planets for that long, all claims of discovering co-orbital planets in other systems to date have either been retracted or disproven. If two planets were discovered in such a formation, I'd guess that they'd both be classified as planets with the special "co-orbital" or "Trojan" appellation given to them, similar to the situation with Saturn's moons Tethys and Dione with their Trojan moons Telesto/Calypso and Helene/Polydeuces respectively, or Saturn's co-orbital moons Epimetheus and Janus.



We don't know that there would be less competition, there is supposed to be a lot of stuff in the Oort, more distantantly spaced out but moving at what seems to us like random.When I referred to "competition", I was talking about competition from similarly-sized bodies - for what should be obvious reasons, a comet's gravity will have little to no effect on a gas giant while the reverse would be true the other way around, with the gas giant's gravity easily affecting the comet's orbit.



Further/higher orbits are higher energy, an object will be travelling faster in a higher orbit, but not moving so many degrees relative to it's primary.I'm pretty sure that's not how orbits work. (https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion#Second_law) Objects move slower the further out they orbit, and only accelerate as they approach periapsis - which is the lowest point in their orbit.



Since an objects gravitational effect is a function of its closeness to another object, the further out an object is orbiting the less of it's orbit it will be dominating at any one time. I would guess as a first approximation that the amount of space dominated would be about the same in a given unit of time, so if an orbit of 10,000 years might be just minimally dominated by an object of some size, an object of the same size in a more distant orbit while still dominating 10,000 years of its orbit (which would be slightly longer, because the speed would be higher because of the higher energy), would not be dominating the whole of it, because the orbit took longer than 10,000 years, I'm not at all sure that time dominated thing is exactly right, but if feels as if it might be in the right sort of order of magnitudes.Whether or not a planetary object is actively exerting significant gravitational force on another solar system body throughout the second body's entire rotation around the sun, the primary body can still be considered to be dominant in its orbit if it "wins" the gravitational tug-of-war whenever the second body brings it close enough; to use a chess analogy, a King and a Queen of opposing sides will not always be near each other, but when opposed solely by a King, the Queen will always win due to its much greater range across the board (which in this analogy represents the much greater gravitational pull exerted by a planet as opposed to, say, an asteroid) - and if the Queen makes the right moves, the Queen can make it so that the opposing King essentially cannot move anywhere without the Queen's "approval" (representing a planet, such as Neptune, pulling objects like the plutinos into an orbital resonance through usage of its gravitational influence).

EDIT:
It also introduces a parameter (big lambda) that characterises the differences between planets and dwarf planets, but I can't work out what units they're using so I can't calculate it for our hypothetical ninth planet. (I think they're using solar masses for the mass unit and AU/Earth years for the SMA/period, but I can't replicate all their calculations that way. Maybe I'm missing something obvious.)

According to Wikipedia, it's called the "Stern-Levison parameter (https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Stern-Levison.27s_.CE.9B)", which is defined as "the object's fraction of solar mass (i.e., the object's mass divided by the Sun's mass) squared, divided by its semi-major axis to the 3/2 power, times a constant 1.7×1016".

[halfeye]

I'm pretty sure that's not how orbits work. (https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion#Second_law) Objects move slower the further out they orbit, and only accelerate as they approach periapsis - which is the lowest point in their orbit.

That's not what I was talking about.

For a circular orbit, the orbital speed is higher at a higher altitude, but the angle traversed is smaller per unit time. This will also be true of more eliptical orbits, but as you say the inner parts of the orbits will be much faster than the outer. If you had two eliptical orbits in the same plane with their foci on one straight line, one outside the other, they would interact, so you can't do that experiment except by running the orbits at different times. The outer orbit has to not cross the inner orbit at any point, otherwise the experiment is confused, but in the case that that is achieved, the outer orbit will be faster in terms of velocity than the inner at the equivalent parts of the orbits, however the inner orbit will be faster in terms of angles traversed, at all equivalent points in the orbits.

[Emperordaniel]

That's not what I was talking about.

For a circular orbit, the orbital speed is higher at a higher altitude, but the angle traversed is smaller per unit time. This will also be true of more eliptical orbits, but as you say the inner parts of the orbits will be much faster than the outer. If you had two eliptical orbits in the same plane with their foci on one straight line, one outside the other, they would interact, so you can't do that experiment except by running the orbits at different times. The outer orbit has to not cross the inner orbit at any point, otherwise the experiment is confused, but in the case that that is achieved, the outer orbit will be faster in terms of velocity than the inner at the equivalent parts of the orbits, however the inner orbit will be faster in terms of angles traversed, at all equivalent points in the orbits.

Circular orbits work the same way as elliptical orbits - just as an example, spacecraft in a low Earth orbit (altitude 160 km) travel at around 7.8 km/s, while the velocity of geosynchronous satellites (altitude 35,786 km) is less than half that, at 3.07 km/s. It's literally the entire reason geosynchronous orbits can only be located at a specific altitude.

[DavidSh]

You can also derive the radius - speed relation for circular orbits from first principles. An object traveling a circular path of radius R with period T must have a speed of 2 pi R/T. It has an acceleration of 4 pi2 R/T2. Newton' law of gravity says that gravity provides an acceleration proportional to 1/R2. Thus T2 is proportional to R3, that is T is proportional to R3/2.

Going back to speed, then, speed is proportional to 1/R1/2. So objects in higher circular orbits move at a lower speed than objects in lower circular orbits.

If you compare this with Emperordaniel's numbers, note that Emperordaniel is using altitude above sea level, rather than orbital radius.

[Ravens_cry]

We must alert Duck Dodgers! (https://en.wikipedia.org/wiki/Duck_Dodgers_in_the_24%C2%BDth_Century)! We must have that Illudium Phosdex! How else will we ever stabilize our dangerously low shaving cream reserves?

Not only dangerously low, alarmingly low! Still, finding it should be simple enough; just follow Planet's A through W, and it will surely be next in line!
OK, in all seriousness, we haven't so much as found Planet X as found evidence that a hypothesized Planet X would explain.

[Max™]

That's why the dominant cosmological paradigm infers the existence of a central black hole. No Black hole has ever been proven to exist on the level that planets in our solar system have been. The standards for confirmation are just so completely different once you leave the solar system. Black holes rest on a chain of assumptions and inferences while planets are much easier to empirically verify.
Observations show numerous stars--with properties which we can use to determine their mass and velocity and such--which are all following orbits around a point that requires there be a certain amount of mass at that point, enough mass that if it were a star it would be BLINDINGLY bright, and impossibly dense... but instead we see nothing there.

There is a huge concentration of matter at the center of the milky way which has numerous stars whipping around it at absurd velocities and which should be easily visible by any number of current telescopes.

You can posit that nature is conspiring to hide this magical ultradense object-which-isn't-actually-a-black-hole if you wish, I suppose, but it isn't a chain of assumptions and inferences. It is observations and stuff like relativity. We're not quite ready to throw that baby out with the bathwater yet, are we?


Conservation of momentum only really applies to rocket propulsion. Helicopters don't care about it2, but don't work in space so nobody is complaining. EM cavity drives still haven't actually been tested in space, only in artificial vacuum chambers on earth where the supposed drive was attached to the wall of the chamber.
So what you're saying is... we need to build a space helicopter?

[halfeye]

Circular orbits work the same way as elliptical orbits - just as an example, spacecraft in a low Earth orbit (altitude 160 km) travel at around 7.8 km/s, while the velocity of geosynchronous satellites (altitude 35,786 km) is less than half that, at 3.07 km/s. It's literally the entire reason geosynchronous orbits can only be located at a specific altitude.

That seems to be correct. I'm thinking about that. :smallsmile:

[Emperordaniel]

That seems to be correct. I'm thinking about that. :smallsmile:

What were you talking about earlier when you said that about orbital speed being higher at a higher altitude, then? :smallconfused:

[halfeye]

What were you talking about earlier when you said that about orbital speed being higher at a higher altitude, then? :smallconfused:

Energy is higher. I assumed that correlated with velocity. I perhaps wasn't allowing for potential energy which is what most of it turns into.

I think, that having a slower speed is less good for dominating an orbit. I thought I was right about the speed being higher with higher orbits, but I also thought that that was countered by the lower angular rate, to the point that the excess speed was entirely countered. If speed is lost, then the lower angular rate is entirely profitable from the point of view of preventing orbit domination.

<edit>

Jupiter dominates the entire inner solar system, the plane of the ecliptic is the plane of Earth's orbit, but effectively it's the plane of Jupiter's orbit, and the rest are dominated into more or less the same plane.

[Max™]

Well yeah, the solar system consists of the sun, jupiter, and some debris.

[Lord Torath]

Energy is higher. I assumed that correlated with velocity. I perhaps wasn't allowing for potential energy which is what most of it turns into.

I think, that having a slower speed is less good for dominating an orbit. I thought I was right about the speed being higher with higher orbits, but I also thought that that was countered by the lower angular rate, to the point that the excess speed was entirely countered. If speed is lost, then the lower angular rate is entirely profitable from the point of view of preventing orbit domination.The thing to remember about orbits is that the orbiting body is falling into the sun (or whatever it's orbiting), but is moving just fast enough sideways that it constantly misses. The farther out you are, the slower you need to go to miss hitting the sun. Mercury has an average orbital speed of 172340 km/hr, while Neptune glides along at 19,590 km/hr.

[RCgothic]

Orbits are cool. I love how completely counter-intuitive they are, such as to catch up to an object in the same orbit you have to first been away from it so that you slow down and fall into an elliptical orbit. That both converts your stored potential energy into excess speed and shortens your path, allowing you to catch up again later in the orbit. Or how to change direction you may be better off burning in the way that you're going so that your apoapsis becomes high and slow, and then change direction there.

Anyway, two bodies in the same orbit is inherently unstable in the long term. The one behind will be accelerated forward, gain speed and go into a higher orbit. The one in front will decelerate and fall into a lower one. I think L4/L5 are only stable for a smaller bodies of negligible mass.

[Max™]

Orbits are cool. I love how completely counter-intuitive they are, such as to catch up to an object in the same orbit you have to first been away from it so that you slow down and fall into an elliptical orbit. That both converts your stored potential energy into excess speed and shortens your path, allowing you to catch up again later in the orbit. Or how to change direction you may be better off burning in the way that you're going so that your apoapsis becomes high and slow, and then change direction there.

Anyway, two bodies in the same orbit is inherently unstable in the long term. The one behind will be accelerated forward, gain speed and go into a higher orbit. The one in front will decelerate and fall into a lower one. I think L4/L5 are only stable for a smaller bodies of negligible mass.

There's a solution with two bodies sharing an orbit:
https://upload.wikimedia.org/wikipedia/commons/7/73/File-Epimetheus-Janus_Orbit.png

From: https://en.wikipedia.org/wiki/Epimetheus_%28moon%29#Orbital_relationship_between _Epimetheus_and_Janus

[Alent]

There's a solution with two bodies sharing an orbit:
https://upload.wikimedia.org/wikipedia/commons/7/73/File-Epimetheus-Janus_Orbit.png

From: https://en.wikipedia.org/wiki/Epimetheus_%28moon%29#Orbital_relationship_between _Epimetheus_and_Janus

Why is that infographic trying to convince us that the two moons make each other change orbital directions?

[Lord Torath]

Wow. Just.... wow.

It's going to take some time to wrap my head around that one.

[ace rooster]

Why is that infographic trying to convince us that the two moons make each other change orbital directions?

It's a rotating frame of reference. One of the moons orbits slightly faster than the frame, and the other slightly slower. When they meet they sort of bounce off each other*, and so the moon that was orbiting faster than the frame ends up orbiting slower, while the moon that was orbiting slower than the frame ends up moving faster. They never change direction, just alternate between being slightly faster and slightly slower than a particular orbital speed.

Think of the drinks trolley on a fast moving train. You would draw it's route relative to the train, which might make it look like it was going backwards, but it is actually always moving in the same direction as the train.

* When they get near each other they pull at each other. The trailing moon gets pulled forward, while the leading moon gets pulled back. A force in the direction of travel will add energy (think engine), while a backward force will remove it (think brake). As we just discussed, higher energy orbits are actually slower, so the trailing moon slows (because orbital energy has increased), while the leading one accelerates (because orbital energy has decreased)! :smallcool:

Presumably their orbits are stabilised by other moons so that they remain circular, so I don't know whether this is a stable solution to the 3 body problem. In reality there are usually more than 3 bodies, and I guess gas giants could stabilise a similar configuration of planets.

That is super cool. Thanks for bringing it up Max.

[Max™]

That is super cool. Thanks for bringing it up Max.

Ain't it though? It's easier to picture it with a visual aid (http://www.skooldays.com/images/ty1427.jpg). If you have them spinning around and the rear one catches the front then they exchange positions it is similar to Epimethus and Janus.

[erikun]

Orbits are cool. I love how completely counter-intuitive they are, such as to catch up to an object in the same orbit you have to first been away from it so that you slow down and fall into an elliptical orbit. That both converts your stored potential energy into excess speed and shortens your path, allowing you to catch up again later in the orbit. Or how to change direction you may be better off burning in the way that you're going so that your apoapsis becomes high and slow, and then change direction there.

Anyway, two bodies in the same orbit is inherently unstable in the long term. The one behind will be accelerated forward, gain speed and go into a higher orbit. The one in front will decelerate and fall into a lower one. I think L4/L5 are only stable for a smaller bodies of negligible mass.
Cruithne (https://en.wikipedia.org/wiki/3753_Cruithne) is a reasonably stable1 asteroid in Earth's orbit path with a 1:1 orbital resonance with Earth, meaning that the two aren't getting any closer/further than they currently are. Cruithne also has a 364-day orbit around the sun, although it sweeps inside Mercury's orbit and outside through Mars's.

Apparently, a big part of the stability there involves Earth and Cruithne exchanging some orbital energy. Earth speeds up just a bit while Cruithne slows down, causing Cruithne to "slow down" until Earth catches up with it in the other direction, at which point the same happens again - Earth will slow down just a bit while Cruithne speeds up, moving away from Earth and looping back around to repeat the process. The whole cycle takes 770 years to complete, assuming I'm reading it correctly.


1 "Reasonably stable" being a relative term. It is doubtful that its orbit will even change within the next several million years, although that is a pretty small amount of time when speaking in astronomy.

[StorytellerHero]

A 900,000 year orbiting planet for another system was recently discovered, so there's now a good example of a Planet X type world.

You can google "Lonely Planet" for the articles that came out last month.

[halfeye]

You can google "Lonely Planet" for the articles that came out last month.

No, you can't it's a trade name for travel books, there are hundreds of books that generate hits before you get anything relevant, "900,000 year orbit" finds it though.