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Jupiter, Saturn, Uranus and Neptune. Those are the gas giants, the four heavyweights of the solar system. But was there once a fifth?
Maybe so, says a new study by David Nesvorny of the Southwest Research Institute in Boulder, Colorado. He used computer simulations to explore what the solar system may have looked like some four billion years ago.
Early on, the giant planets migrated, tugged on each other and generally shook things up before settling into their current orbits. So the simulation tested different initial arrangements of planets to see which would evolve into the solar system we know so well.
With just four giant planets at the outset, the solar system hardly ever wound up looking like ours. But with a fifth planet, the simulations produced familiar solar systems 10 times more often. [David Nesvorny, "Young Solar System's Fifth Giant Planet?" on arXiv.org]
So what happened to the extra planet? It would have run afoul of Jupiter and been chucked into interstellar space. Astronomers have recently discovered that the galaxy is filled with such orphaned planets. Billions of them. So, if an extra planet did get cast out of the solar system, at least it has plenty of company.
—John Matson
[The above text is a transcript of this podcast.]
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20 Comments
Add CommentInteresting. But if this extra planet was jettisoned in some other direction, isn't it most probable that it is still orbiting the sun today, only in a really elongated elliptical orbit? What would it take to eject it entirely from the solar system, and not settling into a new groove in the sun's gravity well?
Reply | Report Abuse | Link to thisWhere might the fifth gas planet have orbited? Between Mars and Jupiter we have the left overs of a rocky planet that broke up, right? And finally, wouldn't a gas planet that was ejected become frozen, thus no longer a gas planet?
Reply | Report Abuse | Link to thisThe thought of so many orphan planets is intriguing. If there are millions or billions of orphan planets in interstellar space, what proportion of the galactic mass do they represent? Do they contribute to the sum of dark matter? What is the chance of such a planet (truly a wanderer) entering our solar system?
Reply | Report Abuse | Link to thisWouldn't this have put Jupiter in an elliptical orbit.
Reply | Report Abuse | Link to thisare there not dust clouds and gases in deep space?
Reply | Report Abuse | Link to thisI'd put more stock in a model that explains the Sun's magnetic field. It could be the result of a merger between two stars and systems in which planets evolved and grouped separately.
Reply | Report Abuse | Link to thisBased on the paper regarding these true wanderers (http://tiny.cc/un4q9) there are ~1.8 times the number of stars in the galaxy of these little guys. Assuming they all weigh in at Jupiter mass, we can calculate that they would represent about 0.01 to 0.02 percent of the mass of the galaxy. Check it out my math here: http://tiny.cc/7gevd
Reply | Report Abuse | Link to thisAlso, dark matter is a different phenomenon than this. These planets are detectable by visual methods; dark matter is matter that we can't detect in that way.
As to the last question, without doing the math, I'd say the chances are pretty small. Space is HUGE; planets are tiny. Go by the numbers: if there are about twice as many unbound planets as there are stars, we'd see about twice the chances of having one of them enter the solar system as having a wayward star enter, which hasn't happened so far as I know. Chances are pretty slim I'd say.
Ooh, that above was supposed to be in reply to milkycoffee...
Reply | Report Abuse | Link to thisThis had been proposed by Tom Van Flandern via the Exploded Planet Hypothesis.
Reply | Report Abuse | Link to thisTom Van Flandern was also a proponent of the idea that ETs made the face at Cydonia on Mars... this and his Exploded Planet Hypothesis were not, so far as I can tell, published in any accredited journal. Not that challenging the scientific mainstream is all bad, but perhaps these hypotheses are just a little too out there.
Reply | Report Abuse | Link to thisOkay...so the inner rocky planets are all contextually different then the outer giant gas planets: What's outlandish about think that they could have formed during different epochs? Notably, there is no stellar companion to our star. A yellow dwarf (like our star) is not usually paired. If another star and associated planets merged with our star, the result could be our solar system with it's strong magnetic influence.
Reply | Report Abuse | Link to thisOkay...so the inner rocky planets are all contextually different then the outer giant gas planets: What's outlandish about think that they could have formed during different epochs? Notably, there is no stellar companion to our star. A yellow dwarf (like our star) is not usually paired. If another star and associated planets merged with our star, the result could be our solar system, rocky inner planets as a result of a previous ecrection and outer gas giants with a center star's and its strong magnetic influence.
Reply | Report Abuse | Link to thisInteresting... any citations or publications I could read about this?
Reply | Report Abuse | Link to thisI don't have any cites except well know main sequence and cataclysmic variable data and .... well the obvious ( I site, the obvious structure of the system.)
Reply | Report Abuse | Link to thisI do need to get into the math.
Any suggestions? Please do not suggest comic books!
Really, I think, this speculation might be easy to prove. Also, any explanation of our systems' structure should include some rationalization of the local matter (particles) which does not exist in isolation and can't be said to have materialized as the consequence of a fa away event. Where is our companion star?
More than likely a stellar collision would generate enough gravitational perturbation to knock any and all planets out of a stellar system. Certainly, there is no reason to suggest our Sun is the result of any sort of collision; evidence suggests it is living a fairly normal life for its type.
Reply | Report Abuse | Link to thisKeep in mind, though the Sun doesn't have a companion (thank goodness!) there are plenty of stars in the Local Interstellar Cloud. And also: the Solar system most likely *did* materialize as the consequence of a far away event-- well not too far: the idea is that nearby supernova(e) caused perturbations in the pre-solar nebula, and eventually denser regions formed stars and their systems, our included.
I agree except for the rocky planets versus the gas giants in our solar system.
Reply | Report Abuse | Link to thisThe perturbation of planets alone can't possibly explain our configuration. As a consequence of the standard model it must be that local objects are tightly bound by gravity and inertia.
Again, the perturbations which created our configuration must have been profound with many, many planet size objects and a great many combinations and collisions of planets, unless it was as massive a disturbance as a star. If it was a star then where is the star? It would be nearby.
Again, I think it is a better explanation then some wandering giant gas planet caused perturbations during formation or early in our stars formation or that our gas giants formed simultaneously within the folds of our stars gravitation field.
The prevalence of orphaned planets in the universe may go a longer way to explaining the "missing mass" than goofball theories about dark matter and dark energy.
Reply | Report Abuse | Link to thisThese theories began as an attempt to explain things that couldn't be seen or measured by the technology available at the time -- the same way other goofball theories begin.
Now we are beginning to discover this missing mass. At the present time we're locating large gas giant planets and only under certain circumstances. As our ability to detect orphan planets increases we will almost certainly find more and smaller planets, and perhaps even planetary systems revolving around a large non-luminous gas giant. These will probably be accompanied by asteroids and meteors attached to that system. There is probably far more conventional material in our universe than we know.
Hocus-pocus theories are not necessary to explain what we cannot see. Wait until we can see it and then venture an explanation. The human desire to find explanations for things can get in our way when we are tempted to invent them.
This all assumes that the computer model was anywhere near to accurate in it's math. With out an indepth analysis of the algorythms used there is no way to give credence to the results of running the model.
Reply | Report Abuse | Link to thisWhile I have no opinion either way on how many planets our system has or had or even what constitutes a planet, I have a very real, experience based opinion on the reliability of computer models. Which is to say that I don't trust them without a great deal of validation and testing.
That paper was not about true wanderers, it was about (apparently) unbound objects in a particular region of one star-forming cloud. One cannot make any broader inferences about unbound object density based on that paper, one way or the other.
Reply | Report Abuse | Link to thisBillions of extrasolar planets? How was this estimate made? I mean we're are just now finding planets around other suns. We need the suns to measure the effect that the planets are having on that sun to even know they are there. Without a sun, these wandering planets would be dark and then there would be no way to even find it.
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