Two large planets may lurk beyond Pluto

[+DieChecker]

Actually the article says the two planets are at probably out at about 200 AUs, where the Kuiper Belt only goes out to about 50 AUs.

Scientists are now thinking that at least 2 more planets may exist in our solar system beyond Pluto. They may be quite a bit larger than Earth.

http://www.space.com...150116_38927567

At least two planets larger than Earth likely lurk in the dark depths of space far beyond Pluto, just waiting to be discovered, a new analysis of the orbits of "extreme trans-Neptunian objects" (ETNOs) suggests.

....

But the actual orbits of the 13 ETNOs are quite different, with semi-major axes ranging from 150 to 525 AU and average inclinations of about 20 degrees.

....

The potential undiscovered worlds would be more massive than Earth, researchers said, and would lie about 200 AU or more from the sun — so far away that they'd be very difficult, if not impossible, to spot with current instruments.

They say right there that it would be difficult to spot these with existing instruments. Even if the diameter is fouror five times that of Pluto, a planet that far out would get less light and the IR signature would be fainter. And so would be harder to detect then even a dwarf planet like Makemake which is about a fifth of the distance, but would have less then a fifth of the diameter.

[Frank Merton]

Another question is how is it objects like that could come to exist out there. One way might be that they are "rogue" planets thrown off from the inner solar system or even another system. The only other way I can imagine is that they formed as planets usually form by accumulating material from around them. Both approaches, while possible, are problematic.

[danielost]

Actually the article says the two planets are at probably out at about 200 AUs, where the Kuiper Belt only goes out to about 50 AUs.

They say right there that it would be difficult to spot these with existing instruments. Even if the diameter is fouror five times that of Pluto, a planet that far out would get less light and the IR signature would be fainter. And so would be harder to detect then even a dwarf planet like Makemake which is about a fifth of the distance, but would have less then a fifth of the diameter.

as i said they, could be in the Oort cloud which is out as far as the solar system reaches. if they are, they would still not have cleared their orbit still making them dwarf planets no matter how big they are.

[godnodog]

The hypothesis is that there are two planets larger than earth orbiting the sun past Neptune and because they are larger than earth they are, by definition, not dwarf planets so just what did Fox News get wrong? BTW, why in the F are you even mentioning Fox News when the article in the OP is from Space.com?

I guess I mixed up the post, thanks for calling out. I did saw a fox news article messing up.

Again thanks for pointing my error

[Waspie_Dwarf]

Another question is how is it objects like that could come to exist out there. One way might be that they are "rogue" planets thrown off from the inner solar system or even another system.

One of the current hypothesis about the formation of the solar system (based on computer modelling) suggests that Jupiter and Saturn at one time had a 2:1 orbital resonance which caused the migration of the objects which now form the Kuiper Belt and Oort cloud. The solar system would have been an extremely chaotic place at that times, with some models suggesting that Uranus was formed further out from the Sun than Neptune and the two planets effectively swapped places.

After the formation of the Solar System, the orbits of all the giant planets continued to change slowly, influenced by their interaction with the large number of remaining planetesimals. After 500-600 million years (about 4 billion years ago) Jupiter and Saturn fell into a 2:1 orbital resonance; Saturn orbited the Sun once for every two Jupiter orbits. This resonance created a gravitational push against the outer planets, causing Neptune to surge past Uranus and plough into the dense planetesimal belt. The planets scattered the majority of the small icy bodies inwards, while themselves moving outwards. These planetesimals then scattered off the next planet they encountered in a similar manner, moving the planets' orbits outwards while they moved inwards. This process continued until the planetesimals interacted with Jupiter, whose immense gravity sent them into highly elliptical orbits or even ejected them outright from the Solar System. This caused Jupiter to move slightly inward. This scattering scenario explains the trans-Neptunian populations' present low mass.

Source: wikipedia

[Waspie_Dwarf]

Again thanks for pointing my error

Read my reply to Merc, it wasn't your error, it was his.

[Waspie_Dwarf]

Actually the article says the two planets are at probably out at about 200 AUs, where the Kuiper Belt only goes out to about 50 AUs.

Beyond the Kuiper Belt is a region known as the Scattered Disc. This is a poorly understood region but the objects within it are believed to have been scattered from the main Kuiper Belt by gravitational resonances with Neptune. This region extends out beyond 100 AU.

The scattered disc (or scattered disk) is a distant region of the Solar System that is sparsely populated by icy minor planets, a subset of the broader family of trans-Neptunian objects. The scattered-disc objects (SDOs) have orbital eccentricities ranging as high as 0.8, inclinations as high as 40°, and perihelia greater than 30 astronomical units (4.5 x 10⁹ km; 2.8 x 10⁹ mi). These extreme orbits are believed to be the result of gravitational "scattering" by the gas giants, and the objects continue to be subject to perturbation by the planet Neptune.

Although the closest scattered-disc objects approach the Sun at about 30-35 AU, their orbits can extend well beyond 100 AU. This makes scattered objects among the most distant and coldest objects in the Solar System. The innermost portion of the scattered disc overlaps with a torus-shaped region of orbiting objects traditionally called the Kuiper belt, but its outer limits reach much farther away from the Sun and farther above and below the ecliptic than the Kuiper belt proper.

Source: wikipedia

[Waspie_Dwarf]

as i said they, could be in the Oort cloud which is out as far as the solar system reaches.

If the hypothesised planets are not Scattered Disk objects (see my post above) then they may, (as is hypothesised for Sedna and 2012 VP113) have originated in the inner Oort Cloud. However they most certainly are not in the Oort cloud now. Theire alculated orbits at 200 AU may put them beyond the outer edge of the Kuiper Belt, but it is way WAY before the inner edge of the Oort Cloud which is estimated to be 2000 - 5000 AU from the Sun.

Gravity diminishes with distance following an inverse square law (in other words double the distance and you only have one quarter the gravitational attraction, triple the distance and you would have one third the gravitational effects and so on).

Even if we assume these objects are at the very nearest edge of the Oort cloud with the closest estimation of where it starts that puts the objects at 2000 AU, ten times further away than the distance estimated for these two objects. If the objects are calculated to be Earth mass then for them to have the same effects ten times further away they would have to have 10² = 100 times the mass. That would make them around the size of Saturn.

[Peter B]

...Gravity diminishes with distance following an inverse square law (in other words double the distance and you only have one quarter the gravitational attraction, triple the distance and you would have one third the gravitational effects and so on).

Ahem. One ninth?

Even if we assume these objects are at the very nearest edge of the Oort cloud with the closest estimation of where it starts that puts the objects at 2000 AU, ten times further away than the distance estimated for these two objects. If the objects are calculated to be Earth mass then for them to have the same effects ten times further away they would have to have 10² = 100 times the mass. That would make them around the size of Saturn.

That's not inherently implausible, is it? There was a British show on TV recently about new theories for the origin of the solar system and it suggested a large planet could well have been ejected from the young solar system through a gravitational interaction with Jupiter as the planets settled into their current positions (didn't get to see it in detail as I was on the phone at the time).

[Waspie_Dwarf]

Ahem. One ninth?

Opps, sorry a touch of brain fade there.

That's not inherently implausible, is it? There was a British show on TV recently about new theories for the origin of the solar system and it suggested a large planet could well have been ejected from the young solar system through a gravitational interaction with Jupiter as the planets settled into their current positions (didn't get to see it in detail as I was on the phone at the time).

It's not impossible but it is not what is being claimed. It's also unlikely.

Gas giants tend to give out a lot more heat than they receive from a process known as the Kelvin–Helmholtz mechanism. Because of their large mass gravity attempts to cause the object to collapse. This shrinking heats up the core.

The up-shot of this is that a gas giant radiates quite brightly in the infrared. A Saturn mass planet at 2000 AU would be a lot easier to see in infrared than an Earth sized planet at 200 AU.

Since 1983 there have been a whole host of orbiting infrared telescopes including IRAS, ISO, AKARI, Spitzer and WISE. None of these have observed any such planet.

Edited January 22, 2015 by Waspie_Dwarf

[Merc14]

Absolutely wrong!

The designation of a solar system object as a dwarf planet has NOTHING to do with it's size.

A planet must satisfy 3 criteria:

1. It must orbit the Sun.
   
2. It must be massive enough to have achieved hydrostatic equilibrium (in other words it must be massive enough that gravity makes the object more or less spherical).
   
3. It must have "cleared it's neighbourhood".
   

Any object which fulfils the first two criteria but not the third is a dwarf planet (regardless of size).

As these two objects are believed to be in the Kuiper Belt they have not cleared their neighbourhood and are, therefore, by definition dwarf planets.

Now that I have had some time to look into this I am not sure I completely agree with your statement that I am "absolutely wrong" any longer. You are correct that upper and lower size and mass limits have not been defined by the International Astronomical Union(IAU) for dwarf planets but it seems that it is assumed that dwarf planets are small objects, smaller than our moon, as per this NASA page https://solarsystem....fm?Object=Dwarf

Second, we have no proof that the two planets in the article didn't clear their neighborhoods. As you stated, they may have been ejected early in the solar system's life after clearing their neighborhoods. Also, in the article linked in the OP, it is clearly stated that the two objects are planets, not dwarf planets as you suggest.

Universe Today has this article on dwarf planets with several links http://www.universet...a-dwarf-planet/ and using the IAU definition describes a dwarf planet as such:

The new classification systems says that bodies that are large enough to have cleared their orbit of planetismals are defined as planets. On the other end of the spectrum, those bodies that are not massive enough to be rounded by their own gravity are defined as small solar system bodies. Dwarf planets are

in between

. There is some controversy about the system that is mainly based on a lack of observation of a few of the dwarf planets.

Space.com http://www.space.com...stem-sdcmp.html uses this reading of the IAU definition:

The International Astronomical Union defines a planet as being in orbit around the sun, has enough gravity to pull its mass into a rounded shape (hydrostatic equilibrium), and has cleared its orbit of other, smaller objects. This last criterion is the point at which planets and dwarf planets differ. A planet's gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit;

the gravity of a dwarf planet is not sufficient to make this happen

.

I understand your reading of the IAU definition and agree that an object as large as say Mercury that hasn't cleared its neighborhood would be labeled a dwarf planet but wouldn't it be more accurate to state that there is still a great deal of argument and controversy about what constitutes a dwarf planet and a planet in the scientific community? NASA, Universe Today and Space.com seem to have taken sides and the director of the New Horizons mission still refers to Pluto as a planet thereby ignoring the DP label completely.

Lastly, no dwarf planet named to date is larger than our moon http://www.space.com...nfographic.html although there is surely far more "large" trans-Neptunian objects than we have seen. If the scientific community decides to call these two objects dwarf planets, as you prefer, I am guessing all hell will break loose with the argument that they may have cleared their neighborhoods before being ejected as part of the debate.

Personally, I find it ridiculous that the IAU didn't address size and mass when creating the label dwarf planet and a tighter definition needs to be agreed upon. Labeling an object the size of Mercury, which certainly is large enough to clear its neighborhood, a dwarf just because there is no neighborhood to clear is absurd. In the meantime, organizations such as NASA are refining the definition themselves and limiting dwarf planets to objects smaller than our Moon.

Edited January 22, 2015 by Merc14

[danielost]

Opps, sorry a touch of brain fade there.

It's not impossible but it is not what is being claimed. It's also unlikely.

Gas giants tend to give out a lot more heat than they receive from a process known as the Kelvin–Helmholtz mechanism. Because of their large mass gravity attempts to cause the object to collapse. This shrinking heats up the core.

The up-shot of this is that a gas giant radiates quite brightly in the infrared. A Saturn mass planet at 2000 AU would be a lot easier to see in infrared than an Earth sized planet at 200 AU.

Since 1983 there have been a whole host of orbiting infrared telescopes including IRAS, ISO, AKARI, Spitzer and WISE. None of these have observed any such planet.

all that can mean is they have been looking in the wrong places. i know the story says that these planets are in the ecliptic. but, they could be outside of it.

[danielost]

Now that I have had some time to look into this I am not sure I completely agree with your statement that I am "absolutely wrong" any longer. You are correct that upper and lower size and mass limits have not been defined by the International Astronomical Union(IAU) for dwarf planets but it seems that it is assumed that dwarf planets are small objects, smaller than our moon, as per this NASA page https://solarsystem....fm?Object=Dwarf

Second, we have no proof that the two planets in the article didn't clear their neighborhoods. As you stated, they may have been ejected early in the solar system's life after clearing their neighborhoods. Also, in the article linked in the OP, it is clearly stated that the two objects are planets, not dwarf planets as you suggest.

Universe Today has this article on dwarf planets with several links http://www.universet...a-dwarf-planet/ and using the IAU definition describes a dwarf planet as such:

The new classification systems says that bodies that are large enough to have cleared their orbit of planetismals are defined as planets. On the other end of the spectrum, those bodies that are not massive enough to be rounded by their own gravity are defined as small solar system bodies. Dwarf planets are

in between

. There is some controversy about the system that is mainly based on a lack of observation of a few of the dwarf planets.

Space.com http://www.space.com...stem-sdcmp.html uses this reading of the IAU definition:

The International Astronomical Union defines a planet as being in orbit around the sun, has enough gravity to pull its mass into a rounded shape (hydrostatic equilibrium), and has cleared its orbit of other, smaller objects. This last criterion is the point at which planets and dwarf planets differ. A planet's gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit;

the gravity of a dwarf planet is not sufficient to make this happen

.

I understand your reading of the IAU definition and agree that an object as large as say Mercury that hasn't cleared its neighborhood would be labeled a dwarf planet but wouldn't it be more accurate to state that there is still a great deal of argument and controversy about what constitutes a dwarf planet and a planet in the scientific community? NASA, Universe Today and Space.com seem to have taken sides and the director of the New Horizons mission still refers to Pluto as a planet.

Lastly, no dwarf planet named to date is larger than our moon http://www.space.com...nfographic.html although there is surely far more "large" trans-Neptunian objects than we have seen. If the scientific community decides to call these two objects dwarf planets, as you prefer, I am guessing all hell will break loose with the argument that they may have cleared their neighborhoods before being ejected as part of the debate.

Personally, I find it ridiculous that the IAU didn't address size and mass when creating the label dwarf planet and a tighter definition needs to be agreed upon. Labeling an object the size of Mercury, which certainly is large enough to clear its neighborhood, a dwarf just because there is no neighborhood to clear is absurd.

the whole dwarf planet thing, was a way to reclassify pluto as a non-planet. it helped when they started finding other small planets out there. personally, i believe pluto and the other dwarf planets are planets. pluto was found by using math. calculations of uranus said there was another planet out there. two men working independent of each other using the math at the time, found pluto. only one got full credit. about ten years after finding pluto, we discovered the math was wrong. i think we were supposed to find pluto when we did.

we have the terrain, gas gaints, ice giants and now dwarf planets. all of them are planets.

[Waspie_Dwarf]

Now that I have had some time to look into this I am not sure I completely agree with your statement that I am "absolutely wrong" any longer.

Merc you were wrong, are wrong and unless the IAU changes it's definition of planets and dwarf planets you will remain wrong.

This is the official definition of planets and dwarf planets from the IAU press release in 2006 which announced the definition:

RESOLUTION 5A

The IAU therefore resolves that planets and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:

(1) A "planet" [1] is a celestial body that (a) is in orbit around the Sun, ( has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and © has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, ( has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], © has not cleared the neighbourhood around its orbit, and

(d) is not a satellite.

(3) All other objects [3], except satellites, orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

Source: IAU

The only mention of mass or size for a dwarf planet is that it must have sufficient mass for hydrostatic equilibrium.

Let's compare that to what I said shall we:

A planet must satisfy 3 criteria:

1. It must orbit the Sun.
   
2. It must be massive enough to have achieved hydrostatic equilibrium (in other words it must be massive enough that gravity makes the object more or less spherical).
   
3. It must have "cleared it's neighbourhood".
   

Any object which fulfils the first two criteria but not the third is a dwarf planet (regardless of size).

As these two objects are believed to be in the Kuiper Belt they have not cleared their neighbourhood and are, therefore, by definition dwarf planets.

Suspiciously similar don't you think? It looks like one of us might know what they are talking about.

Now a reminder of what you claimed:

The hypothesis is that there are two planets larger than earth orbiting the sun past Neptune and because they are larger than earth they are, by definition, not dwarf planets so just what did Fox News get wrong? BTW, why in the F are you even mentioning Fox News when the article in the OP is from Space.com?

(my emphasis).

You made a claim about the definition of a dwarf planet. That claim is absolutely wrong.

Second, we have no proof that the two planets in the article didn't clear their neighborhoods. As you stated, they may have been ejected early in the solar system's life after clearing their neighborhoods. Also, in the article linked in the OP, it is clearly stated that the two objects are planets, not dwarf planets as you suggest.

We have not a shred of evidence that they have cleared their neighbourhood. It looks like you are just wriggling to try and avoid admitting you are wrong.

These objects exist either in the Kuiper Belt or the Scattered Disk. Either way they exist in an area of the solar system which has not be cleared, this means that, whatever size they are, they must, by (the correct not the made up) definition, be dwarf planets.

Personally, I find it ridiculous that the IAU didn't address size and mass when creating the label dwarf planet and a tighter definition needs to be agreed upon. Labeling an object the size of Mercury, which certainly is large enough to clear its neighborhood, a dwarf just because there is no neighborhood to clear is absurd. In the meantime, organizations such as NASA are refining the definition themselves and limiting dwarf planets to objects smaller than our Moon.

Given that until a few posts ago you didn't know what a dwarf planet was and were making totally false claims about them please forgive me if I regard your personal opinion on the matter as totally irrelevant and worthless.

[Merc14]

the whole dwarf planet thing, was a way to reclassify pluto as a non-planet. it helped when they started finding other small planets out there. personally, i believe pluto and the other dwarf planets are planets. pluto was found by using math. calculations of uranus said there was another planet out there. two men working independent of each other using the math at the time, found pluto. only one got full credit. about ten years after finding pluto, we discovered the math was wrong. i think we were supposed to find pluto when we did.

we have the terrain, gas gaints, ice giants and now dwarf planets. all of them are planets.

There is possibly hundreds of Pluto size objects past Neptune so what is to be done? The present definition is inadequate as it stands IMHO and it seems that the astronomical community is not happy with the situation either. Alan Stern a recent Associate Administrator for the Science Mission Directorate at NASA said of the IAU definition (from Wikipedia http://en.wikipedia.org/wiki/Alan_Stern )

Stern has become particularly involved in the debate surrounding the

2006 definition of planet

by the

IAU

. After the IAU's decision was made he was quoted as saying "It's an awful definition; it's sloppy science and it would never pass peer review" and claimed that Earth, Mars, Jupiter and Neptune have not fully cleared their orbital zones and has stated in his capacity as PI of the New Horizons project that "The New Horizons project [...] will not recognize the IAU's planet definition resolution of August 24, 2006."

Stern is no small potato in the space exploration business and is the current PI of New Horizons slated to arrive at Pluto (closest encounter) in 79 days.

[Waspie_Dwarf]

all that can mean is they have been looking in the wrong places. i know the story says that these planets are in the ecliptic. but, they could be outside of it.

If the hypothetical planets were way outside ecliptic the mathematics would show that. These astronomers are not making wild guesses when they come to the conclusion that there are two Earth sized planets at 200 AU, not two Saturn sized planets at 2000 AU, they are using mathematics. Now if you have the mathematics to back up your claim feel free to post it.

You are also assuming that these infrared observatories only observed the ecliptic, that is far from the truth, most of the sky has been observed in the infrared. I repeat, no infrared survey has found candidate gas giants at 2000 AU.

There is yet another problem you haven't considered. Planets at 200 AU would take around 2800 years to complete one orbit of the Sun. At 2000 AU they would take 89,000 years. I suspect his would have a very different effect on the objects being observed.

So the theoretical aspects of science don't back you, the observational aspects of science don't back you, that doesn't leave much.

[godnodog]

Read my reply to Merc, it wasn't your error, it was his.

I was refereing the mention of Fox News, I've could have sweared that the fox article was mentioned here, I stand by the dwarf planets.

Still thank you for commenting

[danielost]

There is possibly hundreds of Pluto size objects past Neptune so what is to be done? The present definition is inadequate as it stands IMHO and it seems that the astronomical community is not happy with the situation either. Alan Stern a recent Associate Administrator for the Science Mission Directorate at NASA said of the IAU definition (from Wikipedia http://en.wikipedia....wiki/Alan_Stern )

Stern has become particularly involved in the debate surrounding the

2006 definition of planet

by the

IAU

. After the IAU's decision was made he was quoted as saying "It's an awful definition; it's sloppy science and it would never pass peer review" and claimed that Earth, Mars, Jupiter and Neptune have not fully cleared their orbital zones and has stated in his capacity as PI of the New Horizons project that "The New Horizons project [...] will not recognize the IAU's planet definition resolution of August 24, 2006."

Stern is no small potato in the space exploration business and is the current PI of New Horizons slated to arrive at Pluto (closest encounter) in 79 days.

i agree those planets have not cleared their orbits. but out pass uranus, it would be impossible for any planet to clear its orbit. everything is just plain to far apart. you also have to remember, the earth has orbited the sun 4.5 billion times where as pluto has only done so around 300 million times. planets further out have done so even fewer times.

[Merc14]

Merc you were wrong, are wrong and unless the IAU changes it's definition of planets and dwarf planets you will remain wrong.

This is the official definition of planets and dwarf planets from the IAU press release in 2006 which announced the definition:

Source: IAU

The only mention of mass or size for a dwarf planet is that it must have sufficient mass for hydrostatic equilibrium.

Let's compare that to what I said shall we:

Suspiciously similar don't you think? It looks like one of us might know what they are talking about.

Now a reminder of what you claimed:

(my emphasis).

You made a claim about the definition of a dwarf planet. That claim is absolutely wrong.

I absolutely agree with you and admitted as much in the above post. Not sure why you missed that as I stated it clearly at least twice.

We have not a shred of evidence that they have cleared their neighbourhood. It looks like you are just wriggling to try and avoid admitting you are wrong.

These objects exist either in the Kuiper Belt or the Scattered Disk. Either way they exist in an area of the solar system which has not be cleared, this means that, whatever size they are, they must, by (the correct not the made up) definition, be dwarf planets.

Not trying to "squirm" out of anything and never said we had proof they cleared their neighborhood. How could I have proof of anything since the planets themselves are hypothetical at this time. If they were created in the inner solar system and then ejected, however, they could've cleared their neighborhood prior to ejection.

Given that until a few posts ago you didn't know what a dwarf planet was and were making totally false claims about them please forgive me if I regard your personal opinion on the matter as totally irrelevant and worthless.

As I said, I agreed with your statement. I also freely admit that I did not know as much as I do now re. dwarf planets and misspoke in that earlier post. You ignore my statements stating that clearly, for some reason but that is your issue, not mine. Being ignorant is not a sin, however, and spurred me to research the subject much more deeply which should be a goal of this forum IMHO. In this case I learned that the definition created by the IAU is rubbish and many agree that it is rubbish (see my above post re. Dr. Alan Stern)

You are, however, duly forgiven, as requested, for ignoring me completely and considering my opinion totally irrelevant and worthless.

i agree those planets have not cleared their orbits. but out pass uranus, it would be impossible for any planet to clear its orbit. everything is just plain to far apart. you also have to remember, the earth has orbited the sun 4.5 billion times where as pluto has only done so around 300 million times. planets further out have done so even fewer times.

I think that is a major problem with the IAU definition. As Waspie said, if the two planets were created out past the Kuiper belt they would be considered dwarf planets because they hadn't cleared their orbits but there is no orbit to clear so we have the dichotomy of two objects of the same size being called different things.

This creates the problem I illustrated with an entity like NASA making their own delineation of what is a dwarf planet based on the IAU definition and relative size. The two popular science sites I linked also use size as a determinant and I am sure if you linked a dozen other astronomy site definitions you'd se they use size as a determinant.

Edited January 22, 2015 by Merc14