Twin Planets

[BobbyJoeCool]

Is it possible for there to be a "twin-planet" situation? So that, a so called "planet" and it's satalite of near-equal size would orbit eachother in much the same way that binary stars do in binary systems?

 

Just a thought...

[insane_alien]

yes. pluto is actually an example of one as the centre of mass is outside the surface of either pluto or charon. ok by recent changes in the definitions pluto and charon are dwarf planets but its the same thing.

 

if you count pluto's other two moons then its a quad system.

[Edtharan]

Earth is nearly a "tein" planet. The size of the moon is very large in comparison to the size of the Earth, compared to the ratios between other planets and their moons (Mars, Saturn, Jupiter, etc).

 

So although Earth and the Moon are not exactly a Twin planert, they are close.

[[Tycho?]]

Yes it is definately possible.

[5614]

http://en.wikipedia.org/wiki/Double_planet

[DaveC426913]

if you count pluto's other two moons then its a quad system.

No. The other two are way too small - and have a correspondingly small effect on the system - to count as anything other than moons.

[Ophiolite]

That might be why insane_alien used the qualifier if. Do you suppose?

[[Tycho?]]

What would posses you to bump an old thread for such a useless statement?

[timo]

;306894'']What would posses you to bump an old thread for such a useless statement?

The same thing that possessed you?

 

I would assume that strictly speaking such a scenario might be impossible. Not because of physics -I see no problem there- but because of the new definition of a planet which, if I got it correctly, requires an object to have no other gravitationally relevant objects in its area to be called a planet. But that´s only pedantry about definitions, of course (not even sure if the definition of a planet really is a hindrance).

[psynapse]

^ Good call.

[[Tycho?]]

http://en.wikipedia.org/wiki/Double_planet

 

There is no formalized definition of double planet. So its not improper to use it, especially in very easy cases like Pluto-Charon where its been called a double planet for quite a long time.

[Ophiolite]

;306894'']What would posses you to bump an old thread for such a useless statement?

Two things:

1) Science demands precision in observation and in reporting. While such precision is typically thought to relate to numbers it should also apply to language. insane_alien made careful use of the qualifier "if" in his post. Had DaveC426913 read what was written, rather than misinterpreted it, then his comments would have been unecessary.

This may appear to be useless to you. I consider it to be of considerable general importance.

2) I have been away from these forums for several months and wished to ease myself back into posting mode with something comparatively lightweight. It would seem some of the reasons for me departing in the first place remain in effect. So sorry to have inconvenienced you.

[[Tycho?]]

Two things:

1) Science demands precision in observation and in reporting. While such precision is typically thought to relate to numbers it should also apply to language. insane_alien made careful use of the qualifier "if" in his post. Had DaveC426913 read what was written, rather than misinterpreted it, then his comments would have been unecessary.

This may appear to be useless to you. I consider it to be of considerable general importance.

2) I have been away from these forums for several months and wished to ease myself back into posting mode with something comparatively lightweight. It would seem some of the reasons for me departing in the first place remain in effect. So sorry to have inconvenienced you.

 

Oh dont mind me, I'm the jerk of these forums. My mission is to keep nonsense to a minimum.

 

As an aside, I disagree with that first argument as yours. Even if you included Pluto's 2 other moons it would no be considered a quadruple system. To be considered a twin planet or double planet, the moon must be of a certain mass. Unofficially, the boundry is if the center of mass of the system is in space between the two bodies. Pluto and Charon orbit around a certain point in space. Earth and Luna do this as well, but the barycenter is inside the surface of the earth, so the Eearth Luna system is not usually considered a double system. Adding in Pluto's two other moons does not significantly change where the Pluto-Charon barycenter lies, hence it would not be a quadruple system. Just as Jupiter is not conisdered a double, triple, or any other sort of system. It has many moons, but these do not significantly contribute to the center of mass of the system.

 

But yeah, dont let me discourage you from posting on these forums, I've been warned by the mods before about my attitude and you seem like a competent poster.