Feasibility of a retrograde planet

I was wondering if a planet could have a retrograde orbit in any fashion stable in a crowded neiboughood like Sun's system.

Also , the ways a retrograde orbit could be achieved are of some interest to me. Free-floater captured , slingshot'd by a close star encounter...

Is there any way this kind of orbit would be stable at the Gy mark ?

And , are there known planets to present this behavior ?

Thank you

"Caution , this post contains broken english inside"

There have been a fair few papers considering retrograde resonances in extrasolar planetary systems.

In fact this appeared on the arXiv today...

the math is a little over my head , but it seems indeed intriguing the coincidence

I'll have to ask for earth's twin detection next

The dynamical fits presented in the present paper tend to
show that, over the eight studied multi-planetary systems,
six of them are liable to be regulated by a mechanism involving
a counter-revolving configuration with a retrograde
MMR. Except for the HD37214 and HD160691 systems for
which the retrograde fits are indeniably bad, the whole of
other fits are slightly better than fits in prograde configurations.
Nevertheless, it remains necessary to perform new
series of observations in order to enlarge the observational
data samples and, as a consequence, to obtain more precise
results.

That was my gut feeling , but i couldn't even begin to formulate the math for it. Nice to know there is work in progress on that.

There's at least one protoplanetary disk (can't think of the system's name) that has one part of it rotating prograde, and another part retrograde.

...and now WASP-17b... WHAT HAVE YOU DONE, CICERON???

Oops...sorry..i'll write a hundred lines "I will not mess with the celestial mechanics" on the blackboard

Now , back on track , what are the chances of a catastrophic event serius enougth to turn a planet orbit all the way backwars , or could cause a debris ring to do a retrograde on its star?

On the other hand , i was under the impression that angular momentum has to be conserved , so , althougth the orbits of other planets can be stabilized , the whole system should act funny , there should be something readly detectable on this kind of systems , an anomaly on the angular momentun versus spectral class. Any studies or thougths on this matter ?

Be rigth back , have to walk the wormhole

Nice work Ciceron =). Now go ask about the feasibility of an Earth-like planet around Alf Cen .

IIRC, if you take any of the planets in the solar system, and make them go retrograde all of the sudden, it actually adds to the stability of the system because the planets spend less time in closer proximity during their close approaches (and thus less gravitational influence over time).

I can imagine planet-planet scattering could induce a retrograde planet, but I can't begin to imagine the odds. I VERY seldom see this when toying around in Gravity Simulator.

So perhaps WASP-17 (and other such... oddballs) had a counter-rotating disk. Is it possible for a stationary, non-rotating cloud to collapse in radial sections? The inner cloud collapses inward into a disk followed by the outer cloud collapsing shortly afterward into another, outer disk? Could this allow for their angular momenta to be different? I can't see how this would be stable in the long run though.

Maybe WASP-17 b got hit hard by something.The planet is very anomalously large. I would think that the impactor would have to be retrograde to produce enough force to do that.

But then how did the impactor get into a retrograde orbit?

I'm stumped.

(Post Scriptum)

Lazarus wrote:...and now WASP-17b... WHAT HAVE YOU DONE, CICERON???

That is the most hilarious thing I have read in the past month, thanks

In fact , i was wondering EXACTLY if a double star system wouldn't be the perfect place for a retrograde planet , more to the point , would it make it easier of more difficult to be detected , say , around Alfa Centaur B ?

I suppose it would make the RV detection more difficult , but if the planet is not in a transing eclising orbit , and the RV variation is masked by other bodies in a regular orbit , we woldn't be capable of detection till the DARWIN mission

And now HAT-P-7b... the plot thickens...

Sirius_Alpha wrote:I can imagine planet-planet scattering could induce a retrograde planet, but I can't begin to imagine the odds. I VERY seldom see this when toying around in Gravity Simulator.

Would be interesting to know what kind of setups you have tried... Coplanar or mutually-inclined? How many planets? 2? 3? more?

Lazarus wrote:Would be interesting to know what kind of setups you have tried... Coplanar or mutually-inclined? How many planets? 2? 3? more?

All coplanar. Usually I spawn a few hundred particles between orbits of various planets in multi-planet system to see how long they would last, sort of like an asteroid belt.

I suspect that the Kozai mechanism may help with getting planets into retrograde orbits - this effect would not occur in coplanar simulations. Might be worth starting the planets off with small mutual inclinations?

IRAS 16293-2422 is the protostar with the counter-rotating disks, by the way (Remijan & Hollis 2006).

Going back to the experiments with Gravity Simulator, going for a combination of planet scattering (by putting the planetary orbits too close together) and Kozai oscillations induced by a binary star companion seems to work quite well at producing retrograde orbits.

Sounds like Alfa Centauri A-B to me
Anyone willing to make a model including retrograde planets around B in a crowded-like system and predict what the ligth curve migth be when a kepler-like resolution telescope take a peek there?

I demand the planet to be named "Rogue" if there is indeed a planet like that in this system

All else held constant, the light curve of a retrograde transiting planet is identical to the light curve of a prograde transiting planet.