Planet 9

[Martian Music]

http://time.com/4184942/planet-9-new-pluto-solar-system/ - http://www.space.com/31671-planet-nine-discovery-explained-infographic.html

Have you guys heard about Planet 9? It's quite interesting and the evidences are there. It's explained in the links above, but if you want a TL;DR, the orbits of mostly-dwarf planet Sedna, and 5 more Kuiper Belt objects are VERY similar to each other, as if a source of gravity near them is influencing their orbits. It's been the case for a while but it's only recently noticed how similar the orbits are.

It's estimated that it would be approximately the size of Neptune. And theoretically it should be affecting the orbits of gas giants like Saturn, but oddly enough, http://www.nasa.gov/feature/jpl/saturn-spacecraft-not-affected-by-hypothetical-planet-9

What do you think?

Oh, here's a nice picture from space.com that explains it:

Edited April 16, 2016 by Martian Music

[Scotius]

I'll believe when i'll see it - literally. We can find Sedna et consortes which are tiny compared to that hypothetical planet, but not the planet itself?

[Steel]

5 minutes ago, Scotius said:

I'll believe when i'll see it - literally. We can find Sedna et consortes which are tiny compared to that hypothetical planet, but not the planet itself?

True, but current estimates put Planet 9 2-5 times further out at perihelion than Sedna, and the best picture we have of Sedna (as far as I can tell) is this from wikipedia

Edited April 16, 2016 by Steel

[Martian Music]

7 minutes ago, Steel said:

True, but current estimates put Planet 9 2-4 times further out than Sedna, and the best picture we have of Sedna (as far as I can tell) is this from wikipedia

Yup, that's the best one Hubble took. And the further something is from the sun, the harder it is to see it. Even if it was big, the tiny amount of light reaching it + the planet's albedo would play the bigger role here.

Edit: Not to mention the gas n dust and other smaller objects getting in the way.

Edited April 16, 2016 by Martian Music

[cubinator]

If "Planet 9" has so many Kuiper belt objects being getting pushed around by it...

...Has it really cleared it's neighborhood?

[Steel]

9 minutes ago, cubinator said:

If "Planet 9" has so many Kuiper belt objects being getting pushed around by it...

...Has it really cleared it's neighborhood?

Let's bear in mind that Jupiter has several thousand (if not many times more) trojan asteroids in it's orbit, but no-one argues that it's not a planet or that it hasn't cleared it's neighborhood.

EDIT: this image shows the situation with Jupiter quite well, with 6,178 trojans found as of Jan 2015 according to the article

Edited April 16, 2016 by Steel

[Martian Music]

I never understood what is meant by "clearing it's neighborhood". Yeah Jupiter faces asteroids in it's orbit, but does it push them away when it's approaching them? And if it does, is that what's meant by clearing the neighborhood?

[cubinator]

13 minutes ago, Martian Music said:

I never understood what is meant by "clearing it's neighborhood". Yeah Jupiter faces asteroids in it's orbit, but does it push them away when it's approaching them? And if it does, is that what's meant by clearing the neighborhood?

I think it means it doesn't share/cross orbits with a bunch of other dwarf planets.

[stupid_chris]

34 minutes ago, Steel said:

Let's bear in mind that Jupiter has several thousand (if not many times more) trojan asteroids in it's orbit, but no-one argues that it's not a planet or that it hasn't cleared it's neighborhood.

EDIT: this image shows the situation with Jupiter quite well, with 6,178 trojans found as of Jan 2015 according to the article

Because those are in the only two Jupiter/Sun stable Lagrangian points, L4 and L5. They've literally been herded there.

And I think the fact that the potential planet kicked all those KBOs into forced orbits illustrates the fact that it's clearing its path, hm?

Edited April 16, 2016 by stupid_chris

[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. 

Although sevenperforce had some interesting ideas on this in another thread. Planet 9 composition

[Kryten]

2 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. 

It will almost certainly have a Stern-Levison parameter above 1, which is the usual definition for 'clearing it's orbit'; it will clearly dominate the dynamics of it's region of the solar system.

[bonyetty]

2 minutes ago, Kryten said:

It will almost certainly have a Stern-Levison parameter above 1, which is the usual definition for 'clearing it's orbit'; it will clearly dominate the dynamics of it's region of the solar system.

Possibly. I was thinking that with such a long orbital period it would be likely not to have achieved this. Oh thanks for the link. I will give it a full read and have a ponder before I nod off. 

[Martian Music]

3 hours ago, bonyetty said:

a new class of object is needed, Giant Dwarf Planet.

I laughed harder than I should at this xD

3 hours ago, cubinator said:

I think it means it doesn't share/cross orbits with a bunch of other dwarf planets.

So asteroids don't count I guess?

And I'm pretty sure Jupiter pushes them out of it's way because otherwise disasters would happen, right?..

Edited April 16, 2016 by Martian Music

[cubinator]

5 minutes ago, Martian Music said:

So asteroids don't count I guess?

Asteroids aren't dwarf planets, and there's loads of them pretty much everywhere, so it's kind of pointless to say there can't be any asteroids.

[Martian Music]

Ah you're right, so clearing the neighborhood is all about dwarf planets (and planets, duh). So Pluto not only crosses Neptune's orbit but gets other dwarf planets in it's orbit?

[Kryten]

3 minutes ago, Martian Music said:

Ah you're right, so clearing the neighborhood is all about dwarf planets (and planets, duh). So Pluto not only crosses Neptune's orbit but gets other dwarf planets in it's orbit?

The thing with Pluto is it's been shunted into a 2:3 orbital resonance with Neptune; so clearly it doesn't gravitationally dominate it's portion of the solar system, Neptune does. 

 

9 minutes ago, cubinator said:

Asteroids aren't dwarf planets, and there's loads of them pretty much everywhere, so it's kind of pointless to say there can't be any asteroids.

Asteroids Ceres and Vesta are considered dwarf planets.

[Martian Music]

1 hour ago, Kryten said:

Asteroids Ceres and Vesta are considered dwarf planets.

See? It's too complicated! ;P

[lude]

Also isn't clearing the neighborhood only about it's own orbit?

 

So that a Pluto who shares it's orbit with stuff that makes up ~92% of mass spinning the same direction is not considered an orbit.

 

But a theoretical large planet that has absolutely nothing sharing it's orbit has cleared it and makes up most of the mass that orbits on it's path.

 

Much like earth has tens of thousands of objects that more or less have the same orbit but the total mass of them is the tiniest fraction of what earth mass is.

 

Or am I wrong here?

 

-- edit --

 

Also haven't large asteroids that can push themselves in a hydrostatic equilibrium been always called dwarf planets?

Edited April 16, 2016 by lude

[Kryten]

The Stern-Levison parameter doesn't depend on what else is in the orbit as such-it's just a statement on how likely an object is to dominate it's orbit given it's size and distance from the star. For example, Pluto in it's current orbit would be considered a dwarf planet even if there were no large planets in the outer solar system; it's just too small to shepherd most of the objects at that distance within the lifetime of the solar system. It could be considered a planet if it was much closer in, or if it was orbiting a much longer-lived star.