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Kepler 11 6 planets system (Read 13633 times)
frankuitaalst
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Kepler 11 6 planets system
02/03/11 at 09:37:58
 
Inputing the basic data from  
http://exoplanet.eu/star.php?st=Kepler-11 gives the following .gsim file  
I've set the not known parameters at random in this simulation .  
The system looks weird , to be honest . It seems I can't get the right "view" .  
Somebody knows whats happening here ?  
BTW : I have no idea how the inclination ,close to 90° for every planet , is defined for this system .  
 
Edit : I have renewed the sim with the Longitude of ascending node set to 0 . Here's the sim . Looks better now
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Re: Kepler 11 6 planets system
Reply #1 - 02/03/11 at 10:09:54
 
the inclination is in respect to our ecliptic I believe and not the systems. If I am remembering all I've read about extra-solar planet data.
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Re: Kepler 11 6 planets system
Reply #2 - 02/03/11 at 12:18:32
 
Inclination is measured from vertical. (0 degrees would be looking  at the system directly from above). An inclination of 90 degrees means we're looking at the system edge on. See http://astro.unl.edu/naap/ebs/animations/ebs.html for an interactive example (of eclipsing binary systems).
 
If the orbit is at 90 degrees, that means the planet's crossing the entire radius of the star, from centre of one limb to the centre of the other. If it's say 88 degrees, then the orbit is tilted a bit, and the planet's path across the star is a chord. I think that also means that the planet orbit is inclined by 2 degrees (=90-88) to our point of view?
 
You could just assume that they're all in the same plane anyway, I guess?
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Re: Kepler 11 6 planets system
Reply #3 - 02/03/11 at 12:23:27
 
I think you're right doctor .  
Makes sense . The statement about the transits makes also sense if you look at the sim abpve , zoom in on the sun and watch how  the tiny little dots transit the solar disc .  
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Re: Kepler 11 6 planets system
Reply #4 - 02/03/11 at 13:52:28
 
Yikes, I didn't realise B and C were so close to eachother!
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Re: Kepler 11 6 planets system
Reply #5 - 02/05/11 at 01:27:33
 
Personally I think this star is in good support of the fission theory of planetary creation. Some stars collapse down from a gas and dust cloud of about a parsec in diameter. At some point they lose angular momentum, and half their mass by the ejection of an equatorial disk. they continue to collapse until they reach a critical density, then they can throw off a series of proto planets, of about Jupiter mass. The rocky metallic cores will be about Earth/Venus mass. The inner proto planets will then lose their atmospheres, as indeed seems to be happening here.
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Re: Kepler 11 6 planets system
Reply #6 - 02/05/11 at 01:48:14
 
I doubt that anything here can't be explained by Migration and orbital interactions.  
 
Kepler 11b at least is interesting - it's 12,334 km in radius (about twice that of Earth), and 4.27 earth masses - that gives it a bulk density of 3250 kg/m³. Either it's a rocky planet with a thick hydrogen/helium atmosphere, or it's a panthalassic world (a rocky planet surrounded by a layer of water hundreds of km thick and most likely a dense atmosphere of water vapour and possibly other gases).
 
11f is even weirder - 16,345 km radius, only 2.3 earth masses, which means its density is 750 kg/m³?! That's only slightly denser than Saturn, it really must be just a ball of hydrogen and helium! 11d is similar too (more massive though, but density is 825 kg/m³)
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Re: Kepler 11 6 planets system
Reply #7 - 02/05/11 at 03:32:55
 
I don't think we can get ourselves a mallet and smash all discovered planetary systems into some sort of modified, or otherwise, "Bode's law". Actually I cannot load that sim, it just stalled the simulator. It might be fun to stick a few resonant planets in there and see what happens to them.
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Re: Kepler 11 6 planets system
Reply #8 - 02/05/11 at 04:16:04
 
Quote from EDG on 02/05/11 at 01:48:14:
I doubt that anything here can't be explained by Migration and orbital interactions.

Kepler 11b at least is interesting - it's 12,334 km in radius (about twice that of Earth), and 4.27 earth masses - that gives it a bulk density of 3250 kg/m³. Either it's a rocky planet with a thick hydrogen/helium atmosphere, or it's a panthalassic world (a rocky planet surrounded by a layer of water hundreds of km thick and most likely a dense atmosphere of water vapour and possibly other gases).

11f is even weirder - 16,345 km radius, only 2.3 earth masses, which means its density is 750 kg/m³?! That's only slightly denser than Saturn, it really must be just a ball of hydrogen and helium! 11d is similar too (more massive though, but density is 825 kg/m³)

 
Interesting stuff indeed . The question that arises to me is how they can estimate a planets mass by transit observation . In the basic article I read, I think ,  they "calcualted" the individual masses from the perturbations of the individual orbits . Mmn hard job , even with the supercomputers used to analyse the stability of the system . On the other hand , this reference seems to indicate that a power law between Mass and Diameter may be proposed of even used .  
http://arxiv.org/PS_cache/arxiv/pdf/1102/1102.0543v1.pdf.  
This idea doesn't correspond with the data mentionned in the post for this system .  
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« Last Edit: 02/05/11 at 10:28:52 by frankuitaalst »  
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Re: Kepler 11 6 planets system
Reply #9 - 02/05/11 at 05:58:01
 
This will probably sound like a really thick question to you guys but I'll ask it anyway.  embarrassed It's age?
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Re: Kepler 11 6 planets system
Reply #10 - 02/05/11 at 07:02:39
 
Now I'm totally confused  undecided For those planets to have migrated in, there must be a third massive body. Then those planets will be in almost perfectly circular orbits but inclined at close to ninety degrees to the sun's equatorial plane. Is there a cut off point, where this stops oscillating?
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Re: Kepler 11 6 planets system
Reply #11 - 02/05/11 at 12:11:50
 
They would probably have migrated in either by gas drag (interacting with gas in the protoplanetary disk) or accretion drag (transfer of angular momentum due to collisions with protoplanets). You don't need a "third massive body".
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Re: Kepler 11 6 planets system
Reply #12 - 02/07/11 at 02:17:32
 
A few of the sources of my confusion here. I'd been confused by the inclination angle but it makes sense to give that angle in terms of the Kepler telescope. So that one's sorted.  
 
Like everyone else, I'd read the science articles and I'd come away with the idea that we were talking about another dwarf star, with close in planets. I assume that the science writers were given a briefing which talked about these stars first then went on to talk about Kepler 11. Result, they nodded off and came away with the idea that it was yet another dwarf.
 
It's not a dwarf, it should stay on the main sequence just a little longer than we will. It's age has got me confused. I'd thought that the spectrum of the star should give us a date for when it joined the main sequence, a bit more precise than plus or minus two billion years.
 
So we're talking about a middle to old age star, which has planets which look like protoplanets. They should have lost their atmospheres. They shouldn't have almost perfect circular orbits.  
 
If the Kozai effect has brought them in very fast, then another hidden body would have had to be at almost ninety degrees to the system. I think that would be highly unlikely but not impossible for one case. However there seems to be loads of giant planets very close in. it doesn't make sense to me at all  embarrassed
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Re: Kepler 11 6 planets system
Reply #13 - 02/07/11 at 11:04:24
 
Quote from Bob on 02/07/11 at 02:17:32:
Like everyone else, I'd read the science articles and I'd come away with the idea that we were talking about another dwarf star, with close in planets. I assume that the science writers were given a briefing which talked about these stars first then went on to talk about Kepler 11. Result, they nodded off and came away with the idea that it was yet another dwarf.

It's not a dwarf, it should stay on the main sequence just a little longer than we will. It's age has got me confused. I'd thought that the spectrum of the star should give us a date for when it joined the main sequence, a bit more precise than plus or minus two billion years.

So we're talking about a middle to old age star, which has planets which look like protoplanets. They should have lost their atmospheres. They shouldn't have almost perfect circular orbits.

 
I'm not sure where you're getting confused here - it IS a "dwarf". Kepler-11 is a yellow G V main sequence star like the sun. Its effective temperature is 5680K, metallicity is solar, radius is 1.1 Sols, mass is 0.95 Sols, and the star is between 6 and 10 billion years old. Our own sun will stay on the main sequence for about 10 billion years, this star is less massive and formed a few billion years before our sun did.  
 
Why do you think it's not a main sequence star?
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Re: Kepler 11 6 planets system
Reply #14 - 02/07/11 at 12:34:25
 
Oops, my mistake,  embarrassed I've been labouring under the impression that dwarf stars were quite a bit less massive than Sol. Finding out hat Sol itself is a dwarf star I take as a a blow to my self esteem. Though I never said this thing is not a main sequence star.  I expressly said that it will reside on the main sequence a little longer than the sun.
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Re: Kepler 11 6 planets system
Reply #15 - 02/07/11 at 12:56:25
 
Yeah, that's why I hate the term "dwarf". Really, it means "Main Sequence star", but because people are so used to hearing about red dwarfs and orange dwarfs (and because of the builtin connotations of the word itself) it's often assumed that the star must be small. It gets even sillier when you realise that A V stars should be called "white dwarfs" (that name's already taken of course) and B stars should be "blue dwarfs", despite the fact that they're more massive than the sun and also are larger in radius! Smiley
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Re: Kepler 11 6 planets system
Reply #16 - 02/07/11 at 13:55:37
 
Well, my defense is always that I'm a bit of an idiot but an idiot interested in space stuff. I have to take solace in the fact that most Guardian readers would read an article about Kepler 11 and decide that this is teeny weeny, so its planets can be close in to something rather cool. Hell they're liberals, they probably don't like the term anyway but demoting our beloved sun into a dwarf is not cricket. I wonder if working astronomers are aware of this.    
 
So, how do these planets keep their atmospheres, they've been bashing round for billions of years, they should be just chunks of rock by now.
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Re: Kepler 11 6 planets system
Reply #17 - 02/07/11 at 15:04:11
 
Quote from Bob on 02/07/11 at 13:55:37:
Well, my defense is always that I'm a bit of an idiot but an idiot interested in space stuff. I have to take solace in the fact that most Guardian readers would read an article about Kepler 11 and decide that this is teeny weeny, so its planets can be close in to something rather cool. Hell they're liberals, they probably don't like the term anyway but demoting our beloved sun into a dwarf is not cricket.

 
Um, let's leave the puerile (and irrelevant) political namecalling out of it, shall we?
 
Quote:
I wonder if working astronomers are aware of this.

 
Most working astronomers don't really care. And "Yellow dwarf" (annoying as it is) has been used for a long time to describe our sun, so it's hardly "demoting it into a dwarf".
 
 
Quote:
So, how do these planets keep their atmospheres, they've been bashing round for billions of years, they should be just chunks of rock by now.  

 
Same way that the planets in our own solar system have kept their atmospheres for 4.6 billion years - their gravity keeps it there.
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Re: Kepler 11 6 planets system
Reply #18 - 02/07/11 at 22:45:27
 
"Um, let's leave the puerile (and irrelevant) political namecalling out of it, shall we?"
 
Politically, I consider myself to be on the liberal left, so my comment was hardly name-calling.
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Re: Kepler 11 6 planets system
Reply #19 - 02/08/11 at 02:27:02
 
Quote from Bob on 02/07/11 at 22:45:27:
Politically, I consider myself to be on the liberal left, so my comment was hardly name-calling.

 
Either way, it's still not relevant here.
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Re: Kepler 11 6 planets system
Reply #20 - 02/08/11 at 07:06:49
 
I've been following this discussion for a while, and just wanted to add a few points.
 
First, I'm pretty confident that we can dismiss the idea of a massive body orbiting in a nearly perpendicular plane to the others. The reason I say this is because if this was the case, the chances that we'd have SIX planets in nearly exactly the same plane becomes vanishingly small. Try it: Add a MJ planet to the system at 0.8 AU with inclination 0° and let the system run for a few hundred millennia. The inclinations of the planets will seem almost random.
 
The other point I wanted to address is the eccentricity of these orbits. I will have to follow up on this, but I believe that planets discovered by transit have an "assumed zero" until further observations based on some other method (i.e. NOT transits). The reason is because we only have ONE POINT (actually, it's a very short arc, but for practical purposes it can be considered a point) on the orbit where we can make observations. Even with repeated observation of the transits, we're still looking at the SAME POSITION in the orbit. Eccentricity can not be determined with only data from a single point.
 
There are three variables we can measure based on the transit: (1) The PERIOD of the orbit (obviously, based on repeated regular intervals between transits), (2) the CROSS-SECTIONAL AREA of the planet (based on how much the star's apparent magnitude decreases during the transit), and (3) the LENGTH OF TIME of the transit, which when combined with the period allows us to calculate the inclination, but ONLY if we assume a very small eccentricity and some diameter of the star based on mass and spectral class.
 
In order to calculate the eccentricity, we'd either need data from (at least) one other point on the orbit, or accurate data on the planet's velocity (relative to the star) at the known point. Transits of planets can give us neither (eclipsing binary stars, on the other hand, readily give us a second data point), but redshift data can fill the velocity gap.
 
Additional Note: While writing this, I was running the modified system as described above with an additional planet. It didn't even take 2000 years before the system was catastrophically disrupted, leaving only 11b, 11g, and the hypothetical "11h" after the collisions and ejections resolved.
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Re: Kepler 11 6 planets system
Reply #21 - 02/08/11 at 07:25:02
 
Quote from Bob on 02/07/11 at 13:55:37:
So, how do these planets keep their atmospheres, they've been bashing round for billions of years, they should be just chunks of rock by now.

 
This is actually an interesting question, because light gasses should be swept away by solar wind. That's why our own inner planets aren't surrounded by vast hydrogen clouds, after all.
 
If I had to guess, I'd say the gas giants in Kepler 11 have very strong magnetic fields. I'd also assume that the star has lower stellar winds than our own sun due to its lower mass.
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Re: Kepler 11 6 planets system
Reply #22 - 02/08/11 at 09:38:40
 
The massive body, if such exists, won't be at ninety degrees to the orbital plane of the planets now but it would have been a long time ago. It's now at about 88 degrees like the planets in the sim. We make it a dwarf of about 0.05 solar masses, at round about the 200 a.u. mark. Then we should have a Kozai cycle of around 6 billion years for those close in planets. The closer in the less their mass seems to matter.  
 
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=426 3492
 
I did watch a little u tube movie but I can't remember what my search terms were, so can't find it again. Does it work or is it a fudge? I don't know but it's certainly interesting.
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Re: Kepler 11 6 planets system
Reply #23 - 02/08/11 at 10:40:14
 
Here's an animation of the Kepler 11 system  
The animation lasts about 15 years.  
One can easily see the plansts perturbing each other , except the outermost one .  
The innermost planets b and c orbits interact strongly . This is not visible in this animation because the timeframes are multiples of the orbital periods .  
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Animation_Kepler11.gif
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Re: Kepler 11 6 planets system
Reply #24 - 02/08/11 at 14:14:36
 
Quote from Bob on 02/08/11 at 09:38:40:
The massive body, if such exists, won't be at ninety degrees to the orbital plane of the planets now but it would have been a long time ago. It's now at about 88 degrees like the planets in the sim. We make it a dwarf of about 0.05 solar masses, at round about the 200 a.u. mark. Then we should have a Kozai cycle of around 6 billion years for those close in planets. The closer in the less their mass seems to matter. 

 
I'm still not seeing why you think there's another massive body, and specifically one that was at 90 degrees to the orbital planet but isn't now.  
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Re: Kepler 11 6 planets system
Reply #25 - 02/08/11 at 14:45:28
 
It's not my idea, and frankly I don't know what to make of it. As I understand it, we have a a binary star system with the planets of the primary star at ninety degrees to the dark companion. Over time with the Kozai mechanism  they rotate 180 degrees. One might think that that's okay but it seems that resonances can occur which disrupt the whole system and pull the planets closer in to the primary.
 
The nearest thing that I can think of, that perhaps bears some relationship to this. is gimbal lock. Having said that, it's just a hunch, I could be way off with that idea.
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Re: Kepler 11 6 planets system
Reply #26 - 02/08/11 at 15:05:13
 
Quote from Bob on 02/08/11 at 14:45:28:
It's not my idea, and frankly I don't know what to make of it. As I understand it, we have a a binary star system with the planets of the primary star at ninety degrees to the dark companion. Over time with the Kozai mechanism  they rotate 180 degrees. One might think that that's okay but it seems that resonances can occur which disrupt the whole system and pull the planets closer in to the primary.

The nearest thing that I can think of, that perhaps bears some relationship to this. is gimbal lock. Having said that, it's just a hunch, I could be way off with that idea.  

 
Yes, but who's saying that there's a binary companion? There's no need for one there at all to explain anything.
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Re: Kepler 11 6 planets system
Reply #27 - 02/09/11 at 01:40:03
 
I did give one link but there are quite a few articles out there, most on the Kozai effect with only one massive planet on close orbit. I expect people are lining up their ducks and waiting on more data. Two rather rough and ready camps, one thinks that the planets were formed further out and migrated in, the other that massive planets can form close in to their primary and keep their atmospheres.  
 
Who cares, it will eventually all come out in the wash. I was hoping though that someone who knows the app would run a sim of a multiple planet with the Kozai effect  taken into account. Simply because it would be a fun thing to do  Smiley Just use the little java script thingy to get some graphs set up. At first blush, it looks as though the Kozai cycle starts in the millions of years, minima to minima, with each planet having it own cycle but later the cycle seems to get longer for all of the planets together, as they come in closer.
 
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Re: Kepler 11 6 planets system
Reply #28 - 02/09/11 at 11:15:06
 
Quote from frankuitaalst on 02/08/11 at 10:40:14:
Here's an animation of the Kepler 11 system
The animation lasts about 15 years.
One can easily see the plansts perturbing each other , except the outermost one .
The innermost planets b and c orbits interact strongly . This is not visible in this animation because the timeframes are multiples of the orbital periods .

If this body was there at 90° inclination , then one can ask : how did it get there ? AFAIK this situation also doesn't correspond with standard formation models.
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Re: Kepler 11 6 planets system
Reply #29 - 02/09/11 at 12:05:10
 
Quote from Bob on 02/09/11 at 01:40:03:
I was hoping though that someone who knows the app would run a sim of a multiple planet with the Kozai effect  taken into account.

 
It can - just create the system in the gravsium as normal (it's been done before here, several times). The Kozai mechanism comes out of it naturally, if you've set it up appropriately.  
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