# Twin Planets! (can two planets share a barycenter and rotate around the same star?)

1. Jun 17, 2010

### koopa12345

for ease of explanation, imagine that the barycenter of two planets is the center of a wheel and that the planets revolve around the edges of the tire. the center of the tire (barycenter) is in orbit around sun, as if the wheel is rolling around in its orbit. my question is, is this possible? of course every time one planet would swing closer to the sun it would be pulled farther out of orbit, but would another large planetary object (perhaps in an outer ring) counter-balance the suns gravity? what possible positioning of these planets might help them maintain their orbits integrity? thanks

2. Jun 17, 2010

### captn

Re: Twin Planets! (can two planets share a barycenter and rotate around the same star

Yes

Isn't your 'two planet' system equivalent to the Earth-Moon system?

Neil

3. Jun 17, 2010

Staff Emeritus
Re: Twin Planets! (can two planets share a barycenter and rotate around the same star

Or at least Pluto-Charon. (Pluto is still a planet in my book!)

4. Jun 17, 2010

### koopa12345

Re: Twin Planets! (can two planets share a barycenter and rotate around the same star

not exactly earth/moon, definitely more pluto/charon, but actually more something like this:

1 = first twin planet
2 = second twin planet
b = barycenter of the twin planets
(the badly typed hexagon [the wagon wheel i was describing] that the planets rest on is their orbit)

.............................................._____ 1____.....................................................
............................................./.................\.....................................................
............................................/...................\....................................................
-->-->-->-->-->-->-->-->-->-/->-->-b-->-->-\->-->-->-->(orbit around the sun)-->
...........................................\...................../...............................................
............................................\.................../..................................................
.............................................\____2_____/.....................................................

it might have been helpful to mention that the planets would be relatively similiar in size. so yea, could this be made possible? or would the sun's gravity pull the planets' out of orbit. and if so, perhaps a balancing body opposite the sun?

5. Jun 18, 2010

### Calluuuum

Re: Twin Planets! (can two planets share a barycenter and rotate around the same star

Isn't this pretty much describing Pluto and Charon? (As Vanadium 50 had said.) Even if people don't consider Pluto a plant, it's still the same thing as what you're talking about. Charon is only just over half Pluto's size (by size I assume you do mean diameter, not mass), but if it works for this pair, I'm sure it could for your described situation.

6. Jun 18, 2010

### koopa12345

Re: Twin Planets! (can two planets share a barycenter and rotate around the same star

ahhhh roight. i guess i could have looked a little further into it before resorting to a forum. thank you!

7. Jun 19, 2010

### nismaratwork

Re: Twin Planets! (can two planets share a barycenter and rotate around the same star

Hehehe... there is a show on NPR called "Says You!" in which one of the bluffing words was "Scruto". In fact it's a trapdoor made of whale bone, but in the midst of flailing for an answer, one of the panelists said, "It's what happened to Pluto".

If Titan is a moon, Pluto is a planet... what is the deal with people getting so antsy over naming conventions anyway? This, in a field where symbolic overload is de rigueur.