Should Trojan planets be called... Planets?

[Spaceception]

Okay, here's the thing, before I give you the info that was in the title, here's the IAU's classification of a planet;

1: The planet must orbit a star(s)

2: It must be roundish

3: It must have cleared its orbit

And 4: It cannot be a Moon

 

So with all of these criteria, would planets that are in Trojan orbit's be classified planets? Or not? And if they were considered planets, that would mean rule 3 for being a planet would be changed, as technically, the orbit's of the planets wouldn't be clear.

Additionally, would counter planets be stable if they had the right conditions? And how many earth sized planets could fit in Earth's orbit before everything got really unstable? And what about Earth sized moons in a Trojan orbit of a gas giant? And if (Theoretically) say, the IAU were stubborn, and wouldn't change what a planet was like, wouldn't that mean the gas giant would be a "Dwarf planet"?

 

Edited April 27, 2016 by Spaceception

[Superfluous J]

I believe 3 is more technical (and convoluted) than how we normally quote it. Actually 2 is as well

But anyway, I'm not 100% sure but I think that so long as they are gravitationally bound together (not interfering with each other) yet still both orbiting the star, they can indeed by called planets according to the IAU.

[Kryten]

'Cleared it's orbit' doesn't mean something has literally cleared out everything in it's orbit, it means it's the dominant object in the dyamics of it's part of the solar system. So no, trojan planets would not count under IAU rules, and the planets shepherding the trojans would definitely count.

As for the rest of it, 'counter-planets' of similar masses would be inherently unstable, and it's not likely you could fit anything close to earth's mass in an earth-like orbit.

[Rakaydos]

If it' a binary star, then a potential planet in the two stars' lagrange point might be considered a planet if it has dominance of it's... lisolje orbit? Did I remember that one right?

[sevenperforce]

1 minute ago, Kryten said:

'Cleared it's orbit' doesn't mean something has literally cleared out everything in it's orbit, it means it's the dominant object in the dyamics of it's part of the solar system. So no, trojan planets would not count under IAU rules, and the planets shepherding the trojans would definitely count.

Although the current definition uses an equation to determine a given object's likelihood of clearing its orbit. If Earth was a Jovian trojan, it would still be in the right zone and mass to fit the equation for clearing its orbit even though it wouldn't. So it would fit the definition for clearing an orbit but would not have cleared an orbit.

3 minutes ago, Kryten said:

As for the rest of it, 'counter-planets' of similar masses would be inherently unstable, and it's not likely you could fit anything close to earth's mass in an earth-like orbit.

Unless it was a double trojan, where the two objects are close in mass and 60 degrees separated in the same low-eccentricity orbit.

1 minute ago, Rakaydos said:

If it' a binary star, then a potential planet in the two stars' lagrange point might be considered a planet if it has dominance of it's... lisolje orbit? Did I remember that one right?

Lissajou.

[Spaceception]

1 minute ago, Kryten said:

'Cleared it's orbit' doesn't mean something has literally cleared out everything in it's orbit, it means it's the dominant object in the dyamics of it's part of the solar system. So no, trojan planets would not count under IAU rules, and the planets shepherding the trojans would definitely count.

As for the rest of it, 'counter-planets' of similar masses would be inherently unstable, and it's not likely you could fit anything close to earth's mass in an earth-like orbit.

But if they were Trojan planets of say roughly the same size, that would mean there are 2 dominant objects in the same orbit, and the dominant object would only be dominant by a little bit.

But instead of binary planets in different orbits, I mean the maximum amount of the same sized planets in the same orbit.

[Gaarst]

4 minutes ago, Spaceception said:

But instead of binary planets in different orbits, I mean the maximum amount of the same sized planets in the same orbit.

2 orbiting each other I guess, as more would probably be unstable and you'd end up with a single bigger planet pretty soon (or a planet and a Moon, cf Earth/Theia)

[sevenperforce]

Just now, Gaarst said:

2 orbiting each other I guess, as more would probably be unstable and you'd end up with a single bigger planet pretty soon (or a planet and a Moon, cf Earth/Theia)

A binary planet is not unstable. Earth and the moon are essentially a binary planet.

[PB666]

5 hours ago, Spaceception said:

But if they were Trojan planets of say roughly the same size, that would mean there are 2 dominant objects in the same orbit, and the dominant object would only be dominant by a little bit.

But instead of binary planets in different orbits, I mean the maximum amount of the same sized planets in the same orbit.

Tidal effects on binary earths would be horrenous, talking about the bay of fundy with 100 meter tides. Martitime cultures would be limited to well protected ports far from the ocean and several serial inlets inside serial bays.

You guys love to fantasize. Too much of a good thing is still too much of a good thing. 

[Spaceception]

3 minutes ago, PB666 said:

Tidal effects on binary earths would be horrenous, talking about the bay of fundy with 100 meter tides. Martitime cultures would be limited to well protected ports far from the ocean and several serial inlets inside serial bays.

You guys love to fantasize. Too much of a good thing is still too much of a good thing. 

not binary planets, Trojan planets, lots of them, I was just showing that picture to show that many, many planets in the HZ are possible.

A scientist made that "Ultimate solar system" btw https://planetplanet.net/2014/05/13/building-the-ultimate-solar-system/

Edited April 28, 2016 by Spaceception

[Superfluous J]

8 minutes ago, PB666 said:

Tidal effects on binary earths would be horrenous, talking about the bay of fundy with 100 meter tides. Martitime cultures would be limited to well protected ports far from the ocean and several serial inlets inside serial bays.

I would assume any binary Earth-sized planets  would have become tidally locked long ago. They'd have tides from the Sun but they'd be lower than ours, not higher.

[PB666]

Tidally locked earths would not have a protective magnetic  feild, the dynamo would falter, and the atmosphere would diasappear. 

 

@Spaceception we first need to find an earth homologue, then we can discuss the potential multiple earth like planets in the core of thier respective habitable zones. 

Edited April 28, 2016 by PB666

[Spaceception]

4 minutes ago, PB666 said:

Tidally locked earths would not have a protective magnetic  feild, the dynamo would falter, and the atmosphere would diasappear. 

 

@Spaceception we first need to find an earth homologue, then we can discuss the potential multiple earth like planets in the core of thier respective habitable zones. 

Not even theoretically?

[kerbiloid]

A new category should be added to the IAU classification: "cheating planet", briefly - a "cheap".

It's like a planet, but is cheating:

• orbits a gas giant
• is a trojan companion for a gas giant
• has a shape of cube
• acts immorally in any other aspect
   

[sevenperforce]

11 hours ago, PB666 said:

Tidally locked earths would not have a protective magnetic  feild, the dynamo would falter, and the atmosphere would diasappear. 

@Spaceception

Any reason why the two planets couldn't have active cores with stable field coupling?

11 hours ago, Spaceception said:

not binary planets, Trojan planets, lots of them, I was just showing that picture to show that many, many planets in the HZ are possible.

A scientist made that "Ultimate solar system" btw https://planetplanet.net/2014/05/13/building-the-ultimate-solar-system/

I talked to him a while back...he erroneously applied the Titus-Bode law to exoplanet systems and didn't factor in Hill spheres, so his systems aren't quite right. 

[fredinno]

On April 28, 2016 at 5:14 PM, PB666 said:

Tidal effects on binary earths would be horrenous, talking about the bay of fundy with 100 meter tides. Martitime cultures would be limited to well protected ports far from the ocean and several serial inlets inside serial bays.

You guys love to fantasize. Too much of a good thing is still too much of a good thing. 

Only they would quickly tidally lock.

Which is also very bad- like on Titan, the oceans would move to the poles.

 

On April 28, 2016 at 5:25 PM, PB666 said:

Tidally locked earths would not have a protective magnetic  feild, the dynamo would falter, and the atmosphere would diasappear. 

 

@Spaceception we first need to find an earth homologue, then we can discuss the potential multiple earth like planets in the core of thier respective habitable zones. 

Well, a large enough planet could just generate a mag. field off its internal heat, even if tidally locked./

In any case, the "ultimate" solar system is way too optimistic. I doubt you could put 2 gas giants in the Sun's habitable zone- though "extended" habitable zones alowing for desert planets and super earths could allow for 2 gas giants (or more)

How such a system forms would be a mystery.

[pincushionman]

If i'm not mistaken, the L4 and L5 Lagrange points (and the others as well, but they're already unstable so it's less of an issue) only really work when the test mass is small compared to both primary bodies.

So a "soft" upper bound to the size of bodies occupying an L4/5. Is my understanding correct?

[sevenperforce]

In a restricted three-body problem, there are some pretty tight upper limits on the masses of the Trojan and the secondary in comparison to the primary. For the purposes of this explanation, I'll let m1 represent the mass of the primary, m2 represent the mass of the secondary, and m3 represent the mass of the Trojan. 

For cases where m2 >>> m3 (e.g. where the secondary is a planet and the Trojan is a satellite or a tiny asteroid), then m1 must be more than 25x m2 in order for m3 to have a stable Lissajou orbit. For the case where m3 and m2 are closer in mass, or where m2/m3 is on the order of m1/m2, then both of those ratios must be greater than 26 in order for m3 to have a stable Lissajou orbit. 

For the extreme case where m2 ≈ m3, a co-trojan (e.g. Earth and Venus in the same orbit), the mass of the primary must be more than 51 times the mass of either secondary.

For the "ultimate solar system" arrangement, Hill spheres need to be taken into account. Jupiter's Hill sphere is massive due to its dramatic distance from the sun, but if it was within the sun's habitable zone, its Hill sphere would be far far smaller. Its moons, in turn, need to have non-overlapping Hill spheres even if they are in resonance. So you can't actually pack nearly as many world-sized moons around a gas giant in the habitable zone as you might think. 

The best chance of having a high-world-density system form is to have a system with several gas giants which collides with a very massive protostellar accretion disk, so that you start with numerous accretion points already "primed".