Planet 9 composition

[PB666]

http://www.bbc.com/news/science-environment-35996813

Well i guess you can hypothesize anything into existence,mbut it seems reasonable, basically what they are saying is there is a cold Neptune out there somewhere. 

[Findthepin1]

It's 700 AU away. How is it as cold as Pluto? Even Enceladus gets colder than -226 Celsius. 

Edited April 11, 2016 by Findthepin1

[Kerbart]

28 minutes ago, Findthepin1 said:

It's 700 AU away. How is it as cold as Pluto? Even Enceladus gets colder than -226 Celsius. 

It gets heated from the inside out. The core is hot and that seeps to the surface

 

[kerbiloid]

Sounds like "We yet haven't found this planet and even not sure if it exists at all, but let's fantasize to keep the theme hot."

[PB666]

3 hours ago, kerbiloid said:

Sounds like "We yet haven't found this planet and even not sure if it exists at all, but let's fantasize to keep the theme hot."

Or maybe its really " if you find it is it worth sending a new horizins like misiion there anytime soon". If they said it was an earth-like planet, or a brown dwarf, i would be concerned about the hype. As it stands it looks like a kuiper belt dust bin not really to much hype there. 

[bonyetty]

If I understand correctly wouldn't it be a dwarf planet by definition as it has not cleared its orbit. Possibly a new class of object is needed, Giant Dwarf Planet. 

Finding it a bit disappointing that some with such positions in astronomy and qualifications continue to keep referring to this new proposed object as 'Planet Nine'.

Edited April 11, 2016 by bonyetty

[sevenperforce]

13 minutes ago, bonyetty said:

If I understand correctly wouldn't it be a dwarf planet by definition as it has not cleared its orbit. Possibly a new class of object is needed, Giant Dwarf Planet. 

Finding it a bit disappointing that some with such positions in astronomy and qualifications continue to keep referring to this new proposed object as 'Planet Nine'.

Oh, it definitely has cleared its orbit, if it exists. "Cleared its orbit" includes being the dominant mass in its neighborhood, like Jupiter to its Trojans. The reason we know anything about planet 9 is precisely because of its gravitational influence on Sedna and the other objects in its neighborhood which don't line up with Neptune. 

[bonyetty]

19 minutes ago, sevenperforce said:

Oh, it definitely has cleared its orbit, if it exists. "Cleared its orbit" includes being the dominant mass in its neighborhood, like Jupiter to its Trojans. The reason we know anything about planet 9 is precisely because of its gravitational influence on Sedna and the other objects in its neighborhood which don't line up with Neptune. 

Dominant mass sounds reasonable so why is Planet defined (from my understanding) using the term "Cleared its orbit" if dominant mass is intended? The use of definitely. Wow impressively confident. Smiley face. If I have a misunderstanding a correction with a reference would be appreciated. 

Edited April 11, 2016 by bonyetty
Smiley face not working

[sevenperforce]

1 minute ago, bonyetty said:

Dominant mass sounds reasonable so why is Planet defined (from my understanding) using the term "Cleared its orbit" if dominant mass is intended? 

Clearing one's orbit is accepted to include maintaining nearby objects in resonant orbits. "Dominant mass" would, I suppose, be less clear. 

I don't much like the IAU definitions...not because I think Pluto should still be a planet, but because objects end up being defined based on their local neighborhood rather than their relationship to their parent star.

 

[bonyetty]

14 minutes ago, sevenperforce said:

Clearing one's orbit is accepted to include maintaining nearby objects in resonant orbits. "Dominant mass" would, I suppose, be less clear. 

I don't much like the IAU definitions...not because I think Pluto should still be a planet, but because objects end up being defined based on their local neighborhood rather than their relationship to their parent star.

 

Ok that would appear to make sense. I like your ideas on the definition. I will have to put some more thinking and reading into that. Thanks. 

[sevenperforce]

21 minutes ago, bonyetty said:

Ok that would appear to make sense. I like your ideas on the definition. I will have to put some more thinking and reading into that. Thanks. 

Sure!

If I had my druthers (which I don't, because no one is going to listen to me when it comes to planet definition schemes), I would start by hammering down the definition of "moon" and "natural satellite".

A "natural satellite" (you could also call it a "dwarf moon" or a "moonlet" but I don't much like those terms) is a self-gravitationally-bound object orbiting a larger body around a barycenter inside that primary. Being self-gravitationally-bound is important; a random chunk of rock or a speck of space dust is a meteoroid, not a natural satellite. Thus the word "natural" serves not only to differentiate it from artificial satellites, but also to identify its formation as natural, i.e., by gravitational accretion.

A "moon" is a natural satellite which is large enough to be gravitationally-rounded.

What, then, is a planet?

A planet is an astronomical body in orbit around the sun which is large enough to have a moon.

This may seem too minimalistic, but it's actually quite specified. Remember that a moon is a type of natural satellite, and a natural satellite must orbit a barycentre inside its primary. Even though Mercury has no satellites and Mars has no "moons" in the sense of a gravitationally-rounded satellite, both are large enough to hold an object like Ceres or Charon or Rhea in an orbit with the barycentre inside it. Pluto, however, is not large enough to maintain a gravitationally-rounded moon (its barycentre with Charon is well out between the two of them) and so it is not a planet. The Pluto-Charon system is a dwarf planet binary.

By comparison, an "asteroid" is a self-gravitationally-bound object in orbit around the sun, and a "dwarf planet" is a gravitationally-rounded object in orbit around the sun which is too small to be a planet.

I think this sorts objects into much more easily recognizable and intuitive classes without depending on concepts like "clearing one's orbit" which depend on many other often-arbitary factors.

[kerbiloid]

1 hour ago, sevenperforce said:

A planet is an astronomical body in orbit around the sun which is large enough to have a moon

http://www.johnstonsarchive.net/astro/asteroidmoons.html

 

Edited April 11, 2016 by kerbiloid

[sevenperforce]

Just now, kerbiloid said:

http://www.johnstonsarchive.net/astro/asteroidmoons.html

 

So?

Asteroids can have natural satellites, but there are no asteroids with moons -- at least, not as I have defined "moon" above.

By defining "moon" as a gravitationally-rounded natural satellite, the definition of "planet" becomes much simpler.

[PB666]

And to think this thread was about composition, not classification. Rather interesting since there is already an active thread open on classification.

[kerbiloid]

Yes, I see now. Haven't got the "moon" definition.

Btw, looks like your defintion of planet is indeed nice.

Edited April 11, 2016 by kerbiloid

[bonyetty]

On 11 April 2016 at 0:57 AM, sevenperforce said:

Sure!

If I had my druthers (which I don't, because no one is going to listen to me when it comes to planet definition schemes), I would start by hammering down the definition of "moon" and "natural satellite".

A "natural satellite" (you could also call it a "dwarf moon" or a "moonlet" but I don't much like those terms) is a self-gravitationally-bound object orbiting a larger body around a barycenter inside that primary. Being self-gravitationally-bound is important; a random chunk of rock or a speck of space dust is a meteoroid, not a natural satellite. Thus the word "natural" serves not only to differentiate it from artificial satellites, but also to identify its formation as natural, i.e., by gravitational accretion.

A "moon" is a natural satellite which is large enough to be gravitationally-rounded.

What, then, is a planet?

A planet is an astronomical body in orbit around the sun which is large enough to have a moon.

This may seem too minimalistic, but it's actually quite specified. Remember that a moon is a type of natural satellite, and a natural satellite must orbit a barycentre inside its primary. Even though Mercury has no satellites and Mars has no "moons" in the sense of a gravitationally-rounded satellite, both are large enough to hold an object like Ceres or Charon or Rhea in an orbit with the barycentre inside it. Pluto, however, is not large enough to maintain a gravitationally-rounded moon (its barycentre with Charon is well out between the two of them) and so it is not a planet. The Pluto-Charon system is a dwarf planet binary.

By comparison, an "asteroid" is a self-gravitationally-bound object in orbit around the sun, and a "dwarf planet" is a gravitationally-rounded object in orbit around the sun which is too small to be a planet.

I think this sorts objects into much more easily recognizable and intuitive classes without depending on concepts like "clearing one's orbit" which depend on many other often-arbitary factors.

Nice and succinct! Curious how round would you define "gravitationally-rounded"? Also have read that Saturn is the least round planet due to its relatively fast rotation. With the possibility of even faster rotating planets (I don't have the phisics knowledge to even guess) could such a planet be less round than say Vesta? As you seem to have put quite some thought into your solar system definitions. If you have the time and sure I don't mind you calling me no one  I am interested in your thoughts. 

Edit not really applicable after a bit of reading https://en.m.wikipedia.org/wiki/Hydrostatic_equilibrium#Planetary_geology

Edited April 16, 2016 by bonyetty

[fredinno]

On 4/11/2016 at 7:57 AM, sevenperforce said:

A "moon" is a natural satellite which is large enough to be gravitationally-rounded.

Phobos and Deimos won't like you

Honestly though, people would get liquided about Phobos losing its "moon" status if you redifined moon like that, just like what happened with Pluto. It's creating one problem by solving another.

On 4/10/2016 at 6:46 AM, PB666 said:

http://www.bbc.com/news/science-environment-35996813

Well i guess you can hypothesize anything into existence,mbut it seems reasonable, basically what they are saying is there is a cold Neptune out there somewhere. 

It should be a super-earth or ice giant, meaning volatile ices (methane, water, ammonia) and hydrogen in the upper layers. What state the hydrogen on the surface will be is up to debate. It may be solid, or the internal heat may heat the hydrogen to a slush or liquid.

Free rocket fuel anyone?

On 4/11/2016 at 6:20 AM, sevenperforce said:

Oh, it definitely has cleared its orbit, if it exists. "Cleared its orbit" includes being the dominant mass in its neighborhood, like Jupiter to its Trojans. The reason we know anything about planet 9 is precisely because of its gravitational influence on Sedna and the other objects in its neighborhood which don't line up with Neptune. 

But Planet 9 orbits so slow, it hasn't really cleared its orbit despite being so massive.

[PB666]

4 hours ago, fredinno said:

Phobos and Deimos won't like you

Honestly though, people would get liquided about Phobos losing its "moon" status if you redifined moon like that, just like what happened with Pluto. It's creating one problem by solving another.

It should be a super-earth or ice giant, meaning volatile ices (methane, water, ammonia) and hydrogen in the upper layers. What state the hydrogen on the surface will be is up to debate. It may be solid, or the internal heat may heat the hydrogen to a slush or liquid.

Free rocket fuel anyone?

But Planet 9 orbits so slow, it hasn't really cleared its orbit despite being so massive.

We can call them moonitoids 

[sevenperforce]

12 hours ago, PB666 said:

16 hours ago, fredinno said:

Phobos and Deimos won't like you

Honestly though, people would get liquided about Phobos losing its "moon" status if you redifined moon like that, just like what happened with Pluto. It's creating one problem by solving another.

We can call them moonitoids 

Better yet, dwarf moons.

16 hours ago, fredinno said:

But Planet 9 orbits so slow, it hasn't really cleared its orbit despite being so massive.

It's forcing orbital periapse arguments for the other bodies, which is exactly what orbit-clearing gravitational dynamical dominance is supposed to do.

[sevenperforce]

'Twas pointed out to me elsewhere that Pluto is large enough to retain Rhea as a "real" moon -- that is, with the barycentre inside of Pluto.

However, Pluto would still become tidally locked to Rhea in astronomically brief time.

Thus, I propose an adjusted definition for "natural satellite". A natural satellite is a self-gravitationally-bound object orbiting a barycentre inside a larger body, too small to force mutual tidal locking with the larger body. This makes intuitive sense; if two objects are tidally locked then they are orbiting each other, even if the barycentre is within one body. 

A moon is a gravitationally-rounded natural satellite of a substellar object. A planet is a body large enough to have a moon. This cutoff is about 6.3e22 kg, comfortably greater than the mass of Eris but comfortably lower than the mass of Mercury. A dwarf planet is a gravitationally-rounded body too small to have a moon.

[PB666]

17 hours ago, fredinno said:

Phobos and Deimos won't like you

Honestly though, people would get liquided about Phobos losing its "moon" status if you redifined moon like that, just like what happened with Pluto. It's creating one problem by solving another.

It should be a super-earth or ice giant, meaning volatile ices (methane, water, ammonia) and hydrogen in the upper layers. What state the hydrogen on the surface will be is up to debate. It may be solid, or the internal heat may heat the hydrogen to a slush or liquid.

Free rocket fuel anyone?

But Planet 9 orbits so slow, it hasn't really cleared its orbit despite being so massive.

Won't be rocky. Here is the reason why.

If it is as large as Earth or larger.

1. Its too far away from the Sun to have its atmosphere stripped by solar winds
2. Instead it will be condensing hydrogen, carbon dioxide, nitrogen from space.
3. Unlike solids that may get thrown into bizarre orbits, gases undergo frictional energy loss and fall into the orbiting body without solar winds to kick the out they will collect.

Nitrogen would liquidfy
Carbon dioxide will solidfy and sink in the liquid nitrogen
Hydrogen would compose the atmosphere, but disolve and occasionally react with nitrogen forming ammonium H2N2 and with carbon diozied froming carbon monoxide and ice. While this expected it would be infrequent since in the atmosphere of the planet we expect plasma will create a positive charge on the leading edge can electricity would flow into the atmosphere causing eventually charge cancelation and molecular formation. Since most of this will occur in the upper atmosphere, the heavier stuff would only circulate upwards in strong storms, or co-gravitate with hydrogen and thus the composition is minor. Carbonated Ice will be the heaviest in hot spots (volcanic, but nine may be so old, it does not need to be the same age as our system, it could have been a neutron star or a planet from a system that went supernova during the previous generations of stars so volanism may not be major). the carbon oxygen and hydrogen could react forming complex rocks and other organics, which would litter the liquid surface of the planet in a very thin layer, followed by frozen carbon dioxide, ice, liquid nitrogen, pools of liquid hydrogen and mostly gaseous hydrogen.

[sevenperforce]

4 hours ago, PB666 said:

Carbonated Ice will be the heaviest in hot spots (volcanic, but nine may be so old, it does not need to be the same age as our system, it could have been a neutron star or a planet from a system that went supernova during the previous generations of stars so volanism may not be major).

Could have been a neutron star? I don't think so.

[fredinno]

6 hours ago, sevenperforce said:

Better yet, dwarf moons.

It's forcing orbital periapse arguments for the other bodies, which is exactly what orbit-clearing gravitational dynamical dominance is supposed to do.

But wouldn't objects move back in during its million-year orbit?

6 hours ago, sevenperforce said:

'Twas pointed out to me elsewhere that Pluto is large enough to retain Rhea as a "real" moon -- that is, with the barycentre inside of Pluto.

However, Pluto would still become tidally locked to Rhea in astronomically brief time.

Thus, I propose an adjusted definition for "natural satellite". A natural satellite is a self-gravitationally-bound object orbiting a barycentre inside a larger body, too small to force mutual tidal locking with the larger body. This makes intuitive sense; if two objects are tidally locked then they are orbiting each other, even if the barycentre is within one body. 

A moon is a gravitationally-rounded natural satellite of a substellar object. A planet is a body large enough to have a moon. This cutoff is about 6.3e22 kg, comfortably greater than the mass of Eris but comfortably lower than the mass of Mercury. A dwarf planet is a gravitationally-rounded body too small to have a moon.

But the Earth will eventually tidally lock with the moon (the Sun will probably not consume Earth). Is the Moon no longer a moon then?

5 hours ago, PB666 said:

Won't be rocky. Here is the reason why.

If it is as large as Earth or larger.

1. Its too far away from the Sun to have its atmosphere stripped by solar winds
2. Instead it will be condensing hydrogen, carbon dioxide, nitrogen from space.
3. Unlike solids that may get thrown into bizarre orbits, gases undergo frictional energy loss and fall into the orbiting body without solar winds to kick the out they will collect.

Nitrogen would liquidfy
Carbon dioxide will solidfy and sink in the liquid nitrogen
Hydrogen would compose the atmosphere, but disolve and occasionally react with nitrogen forming ammonium H2N2 and with carbon diozied froming carbon monoxide and ice. While this expected it would be infrequent since in the atmosphere of the planet we expect plasma will create a positive charge on the leading edge can electricity would flow into the atmosphere causing eventually charge cancelation and molecular formation. Since most of this will occur in the upper atmosphere, the heavier stuff would only circulate upwards in strong storms, or co-gravitate with hydrogen and thus the composition is minor. Carbonated Ice will be the heaviest in hot spots (volcanic, but nine may be so old, it does not need to be the same age as our system, it could have been a neutron star or a planet from a system that went supernova during the previous generations of stars so volanism may not be major). the carbon oxygen and hydrogen could react forming complex rocks and other organics, which would litter the liquid surface of the planet in a very thin layer, followed by frozen carbon dioxide, ice, liquid nitrogen, pools of liquid hydrogen and mostly gaseous hydrogen.

"Could have been a Neutron Star"

I suppose that was a joke?

Also, the atmosphere would likely be liquid, the black-body temperature at its orbit approaches interstellar temperatures of 4K. Internal heating doesn't penetrate well into the upper atmosphere, and it can only do so much.

[sevenperforce]

On 4/18/2016 at 7:18 PM, fredinno said:

On 4/18/2016 at 10:50 AM, sevenperforce said:

[Planet 9 is] forcing orbital periapse arguments for the other bodies, which is exactly what orbit-clearing gravitational dynamical dominance is supposed to do.

But wouldn't objects move back in during its million-year orbit?

Nah. Planet 9's subtle adjustment to the sun's gravity well extends all the way across the solar system; it's not like its gravitational influence just drops to zero when you get far enough away. Otherwise the L3 Lagrange point wouldn't be a thing.

On 4/18/2016 at 7:18 PM, fredinno said:

But the Earth will eventually tidally lock with the moon (the Sun will probably not consume Earth). Is the Moon no longer a moon then?

Under my definition? No, it wouldn't be. Right now, the moon is tidally locked to Earth but Earth is rotating independently of the moon. When the dynamics of the system shift so that both Earth and the moon are tidally locked to each other, it will become a double-planet system.

I mean, we would still probably call it "the moon" for the sake of history, but there's nothing wrong with recognizing such a change. After all, the Earth and the moon are already very close to being a double-planet system; the moon doesn't actually go around the Earth at all. They're just in very close solar orbits and the Earth's gravity perturbs the moon's solar orbit enough to tidally lock it and make it appear to orbit Earth.

[Thomassino]

Its composition would really depend on what planet type it actually is. Also on origin place, it could have formed back there in Kuiper belt (but I strongly doubt it), within Neptune's orbit or it could even be caprured interstellar object.

So it is really hard to tell until we get more data, and confirm it even exist