Did Jupiter toss a giant planet out of the solar system?

By Phil Plait | November 16, 2011 12:00 pm

What did the early solar system look like?

A new study has come out conjecturing that there used to be five giant planets in our solar system, and one got ejected by Jupiter through its gravitational influence. It’s an interesting bit of research, based on computer modeling.

It’s pretty well established that the outer planets have moved around a bit since the solar system formed, with a possibility that Uranus and Neptune even swapped places! But the models have a hard time explaining how this could’ve happened without Jupiter totally messing up the inner solar system. The models seem to indicate the orbits of Mars and Earth would not look at all as they do today if this were the case.

Using the known math of physics and gravity, the author of this new study set about trying to figure out how this might be the case, and got the idea that maybe there was a fifth big planet back then, billions of years ago, with perhaps the mass of Uranus. He found that under certain circumstances, he could show that the addition of this planet explains the way both the outer and inner solar system look today, and why we don’t see this planet any more, since it was tossed out of the solar system through interactions with Jupiter.

All in all, a nice result. I want to stress, though, that it’s not set in stone. Basically, it’s a cool idea supported by models, but we don’t know how real it is. Maybe there’s something else we don’t know: maybe there were two extra planets, or maybe Jupiter interacted with the three other giant planets in a different way. I got email from some friends about all this, and I stressed that this is a model, not evidence. We do know that rogue planets roam the galaxy, and they were almost certainly ejected in this manner, so the idea of a lost solar system planet isn’t crazy! But it’s only one possible scenario. There are lots of other possibilities.

I was pleased to see Alan Boyle MSNBC’s Cosmic Log made the same case. A story like this is a bit sexy, and I was wondering if some venues might run away with it, so it’s good to see some solid reporting on it!

And it’s interesting to think that somewhere out there, light years away, a lonely, dark, and slowly freezing planet may be bulleting through the galaxy. If we ever do develop interstellar travel, will our descendants stumble on that planet? It’s a romantic thought.

CATEGORIZED UNDER: Astronomy, Cool stuff

Comments (61)

  1. Gary

    How does a huge planet actually get “tossed out?” Could you be more specific on the implications for orbits of other planets? It must take a huge amount of energy to send a planet beyond the grasp of solar gravity and it has to come from the other planets, right?

  2. Eric

    Actually – that ‘rogue planet’ notion worries me; isn’t it just another way the universe is trying to kill us? If such a planet passed through our solar system (admittedly *very* unlikely an event to happen), how much disruption could it cause to our orbit? Or that of some asteroids that would otherwise never be a threat? Or some Oort-cloud/Kuiper belt objects – that then give us an extra chance of being hit by a comet…

  3. QuietDesperation

    Reminds me of a line from a Michael Moorcock novel involving time travel, and how it’s not easy building a picture of the multi-billion year timeline based on random, scattered reports from time travelers.

    “As a consequence our knowledge of the future is sketchy, to say the least: we have no idea of how civilizations will grow up or how they will decline; we do not know why the number of planets in the Solar System seems to vary drastically between, say, half-a-dozen to almost a hundred; “

  4. Mike H

    How accurate are these models? Any chance of pointing telescopes on a particular point in the sky based on this idea and finding something?

  5. Makes you wonder if a large or even small planet out there is lurking through space, headed right for our solar system.

    “Everyone, here is our new planet, his name is Nubert. Lets all help him fit it. No! Nubert, do NOT crash into the other planets! That’s time out for you, mister!”

    (Of course that all depends on trajectory and speed and the like)

  6. fintin

    Wow. This really make me think about how far that planet (if real) traveled over all these years.

  7. You know, the planet´s full name is Neil DeGrasse Jupiter.

  8. Peter Tibbles

    If our descendants encountered this planet, how would they know it was from our solar system?

  9. Dustin J

    Couldn’t have been a planet. If Jupiter kicked it out of the system, then it never cleared it’s orbit and thus could only be a dwarf gas giant. ;-)

  10. Chris Winter

    The paper suggests this happened about 600 million years after the solar system formed — i.e. about 4 billion years ago.

    What I wonder is: How did it affect the asteroid belt?

  11. anevilmeme

    There’s a plot for a Dr Who episode here……

  12. Tezcatlipoca

    I saw a program on the Science channel that postulated that both Jupiter and Saturn had orbits that brought them within Earth’s orbit and speculated that this is what prevented a planet from forming between Mars and Jupiter therefore resulting in the asteroid belt. This study is interesting too. It seems wild that a Neptune or Uranus sized planet can get ejected out of a planetary system but that’s what it looks like happens.

  13. RaginKagin

    Oh great, more science for the Planet X people to exploit…lol

  14. According to my dubious math, if the planet in question were ejected at about 45 kilometers per second (maybe someone can give me a better number, but solar escape velocity and them some is what I used), that translates to 1.42 billion kilometers a year. Not a terribly high speed, as cosmic objects go, but 4 billion years is a long time! Multiply 1.42 billion kilometers by 4 billion years, and you get something on the order of 600,000 light years! That’s about 12 Milky Way radii!

    However, 45 k/s isn’t anywhere close to galactic escape velocity, so in reality, the planet would not leave the galaxy (unless it happened to get another slingshot assist from a particularly massive object, like a black hole). As it orbits the galaxy, it’s going to get tugged this way and that by the other stuff orbiting the galactic center. It’s a highly chaotic system. So actually, even if we could confirm that the planet existed, and even if we could somehow calculate exactly how fast it left, and even if we could figure out exactly what direction it traveled, we would still have absolutely no way of knowing where the planet is now. For all we know, it could have circled the Milky Way 40-odd times, and could come blundering back into our solar system, and we’d never recognize it as our long lost planetary buddy.*
    Still, that’d be a great disaster-movie twist, wouldn’t it? Not only is that rogue planet from who-knows-where threatening the Earth and everyone on it, but it was originally from here! The call planet is coming from inside the solar system!

    *We’re talking “Winning the lottery ten million times in a row” unlikely

    PS: Please, PLEASE feel free to correct my math, which is a conglomeration of Googled factoids and numbers pulled out of you know where.

  15. ”””I was pleased to see Alan Boyle MSNBC’s Cosmic Log made the same case. A story like this is a bit sexy, and I was wondering if some venues might run away with it, so it’s good to see some solid reporting on it!
    And it’s interesting to think that somewhere out there, light years away, a lonely, dark, and slowly freezing planet may be bulleting through the galaxy. If we ever do develop interstellar travel, will our descendants stumble on that planet? It’s a romantic thought.””””

    You are so ‘Different’…. Lol

  16. Peter B

    Joseph G @ #11: I checked your maths, and I agree with your 600,000 light year calculation.

    So given the diameter of the Milky Way is ‘only’ 100,000 light years, you’ve demonstrated to this little black duck’s satisfaction that this planet would have had time to reach any point in the galaxy in the intervening time.

  17. @13 Peter: Thanks. It really stretches the mind to try to consider billions of billions of… anything! Space is big, but so is time.
    I wonder if there’s a way to determine exactly how fast such an object could have been ejected by an interaction with Jupiter?

  18. Kevin

    I feel bad for this lonely cold planet. I therefore propose it be named “Melancholia”.

  19. So ..do we call this hypothetical lost world Mondas or Mongo? ;-)

    (Yeah, both those fictional planets are much less massive than the one imagined here, I know. Mongo even gets described (clearly wrongly) as a “comet” at one point.)

    How does this match with earlier predictions of a possible tenth planet larger than Jupiter in the Edgeworth-Kuiper cometary belt (or was it Oort cloud?) noted here earlier this year / late last year btw?

  20. Messier Tidy Upper

    @1. Gary : “How does a huge planet actually get “tossed out?”

    Well “huge” is a relative term and compared with Jupiter or Saturn, Neptune mass planets are fairly small although still huge compared to Earth – which, of course, is huge compared with planets like Pluto.

    When you get two gas giants tangling eccentric and messed up orbits and ejections from the planetary system can happen pretty easily as our exoplanetary discoveries seem to indicate.

    We may have got off lightly here as Planet-hunter Paul Butler observes :

    ” .. If Saturn were about twice as massive, it would gravitationally interact with Jupiter on a short timescale. One of them would get thrown in and the other would be thrown out – and we wouldn’t be here.”

    Source : Paul Butler, page 41, Extreme Universe, Nigel Henbest & Heather Couper, Channel 4 Books, 2001.

    So losing one Neptune mass world ain’t too bad all things considered really! ;-)

  21. NoAstronomer

    “dwarf gas giant”

    I LOL’d.

  22. Messier Tidy Upper

    @14. Joseph G :

    According to my dubious math, if the planet in question were ejected at about 45 kilometers per second (maybe someone can give me a better number, but solar escape velocity and them some is what I used), that translates to 1.42 billion kilometers a year. Not a terribly high speed, as cosmic objects go, but 4 billion years is a long time! Multiply 1.42 billion kilometers by 4 billion years, and you get something on the order of 600,000 light years! That’s about 12 Milky Way radii! However, 45 k/s isn’t anywhere close to galactic escape velocity, so in reality, the planet would not leave the galaxy …(snip) … As it orbits the galaxy, it’s going to get tugged this way and that by the other stuff orbiting the galactic center. It’s a highly chaotic system. So actually, even if we could confirm that the planet existed, and even if we could somehow calculate exactly how fast it left, and even if we could figure out exactly what direction it traveled, we would still have absolutely no way of knowing where the planet is now. For all we know, it could have circled the Milky Way 40-odd times ..

    Forty odd times seems unlikely unless it was somehow much closer to the Galactic Centre in a much smaller galactic orbit. For reference :

    “Since our Sun was formed more than 4 billion years ago, it has travelled around the Galaxy 16 times.”
    “Two of the Milky Way’s Spiral Arms Go Missing.” NASA e-newsletter news release 2008-June-4th.

    My rough guess would be that this wandering ex-solar system world would have made about the same number of galactic orbits give or take a few depending on whether it ended up much inside or outside our orbit and how perturbed its galactic orbit might have been by encounters with other stars, brown dwarfs and perhaps rogue planets.

    I know its incredibly unlikely but I also wonder whether this world could have been captured into orbit around another star and “adopted” into another planetary system?

    @18. Kevin : “I feel bad for this lonely cold planet. I therefore propose it be named “Melancholia”.

    Hmm.. How about The Black Sheep Planet because it got kicked out of the family – and if it ever returns to our solar system we could call it the Prodigal Planet? ;-)

    @9. Dustin J :

    “Couldn’t have been a planet. If Jupiter kicked it out of the system, then it never cleared it’s orbit and thus could only be a dwarf gas giant.”

    Exactly. Seconded by me. :-)

    That’s *if* you accept the IAU’s idiotic* definition of planet which I, like many others, do not.

    ——

    * Alan Stern’s word for it not mine.

  23. MichaelL

    Quick! Someone call Roland Emmerich! I think he can use this idea in a new movie!

  24. Messier Tidy Upper

    @21. NoAstronomer : “dwarf gas giant” I LOL’d.

    Exoplanet hunter Sara Seager has coined the term ‘gas dwarf’ for very small gas giants discovered orbiting other stars – a number of so-called “SuperEarths” (esp. the higher mass ones) may actually belong to this planetary species. A class which like the Super-Earths, Hot-Jupiters & Eccentric Orbiters is unrepresented in our own solar system.

    Neptune and Ouranos are often classed as “ice giants” rather than “gas giants” because these less massive mostly gaseous worlds probably contain a lot more water than the almost all hydrogen and helium composition of Saturn and Jupiter. The term ice giants (& gas dwarfs) also matches the Pluto type planets the ice dwarfs – the most numerous and most recently discovered category of planet in our solar system.

  25. Infinite123Lifer

    For #4:

    Don’t you think 600,000 light years is a little harsh for a time out? Sounds like Nubert was sent into exhile. :)

    You gotta love naming hypothetical model planets and rendering them acting human!

    Melancholia left and she never came back.

    Poor Mondas, we never heard from him again.

    Mongo, if it wasn’t for you our model just wouldn’t work.

    Remember our long lost planetary buddy? Yeah, me too. Things just haven’t been the same without him.Thank the orbits he never came back though ;)

    Peace out Rogue!

    Yeah ol’ Black Sheep Planet went off the deep space.

    Anyone seen the Wandering Llost Planet World Lately? MIA as usual.

    Here’s to you hypothetical planet!

  26. amphiox

    Couldn’t have been a planet. If Jupiter kicked it out of the system, then it never cleared it’s orbit and thus could only be a dwarf gas giant.

    Well, up to the moment of the ejection, JUPITER was only a dwarf gas giant too, as it hadn’t YET cleared its orbit!

    The IAU definition doesn’t work, obviously, for planetary systems that are still in their early formation periods.

    (Also, after ejection, it STILL wouldn’t be a planet, because it isn’t orbiting a star….)

    Forty odd times seems unlikely unless it was somehow much closer to the Galactic Centre in a much smaller galactic orbit.

    I suppose if it was ejected towards the galactic core, it could have fallen into a highly elliptical orbit which overall would have been much shorter than the solar system’s own orbit, allowing it to get forty odd revolutions in?

    which, of course, is huge compared with planets like Pluto

    Sneaky, Messier, sneaky. Smuggling in non-IAU usages of the term back into popular discourse like that. Is this part of your grand conspiracy to get the definition you disapprove of changed? Because if the majority of astronomers reject the official definition and stop using it that way in their scientific communications, then the whole purpose of having an official definition is nullified, and either the IAU will be forced to change the definition, or the official definition will fall into disuse, die a slow ignomious death, and the common usage will de facto replace it.

    If our descendants encountered this planet, how would they know it was from our solar system?

    Isotopic analysis ought to be able, in theory, to show that the planet formed from the same primordial gas cloud as the sun. Although that may not completely prove it came from our solar system, as I think the current theory is that several stars in addition to our sun formed from that cloud.

  27. Krashnark

    I wonder if this possible planet would make some people crankier than others /s. The thing is relatively stuck in one of the zodiac signs to us after all and we all know mass and distance does not matter in astrology.

    On a serious note, would the hypothetical planet even still be on our orbital plane if stretched out to it? The sun has done a lot of migrating in that time period.

  28. Tim

    Lewis Says:
    November 16th, 2011 at 2:08 pm

    Makes you wonder if a large or even small planet out there is lurking through space, headed right for our solar system.

    I think Nancy Lieder and her Zetatalk gang are way ahead of you on that. :P

    I imagine Nancy is receiving messages from the Zetas and Xenu, who are telling her it’s Planet X.

  29. CR

    Ah, what the heck, as long as we’re just speculating…

    amphiox’s last point about analysing the isotopes of various planets to see from which star(s) they may have come inspired this idea: might the local stellar group ‘share’ planets among themselves? Maybe there’s a type of ‘planet swapping’ among young solar systems as they spread out from their respective nebulae. In addition to the stars of the group sharing similar traits, perhaps their planets (if they have any) also share similarities, further identifying the local group as ‘siblings.’

    Or not… this really is the realm of sci-fi tv at this point, but it was kind of fun all the same.

  30. VinceRN

    My skeptisism gland always twitches a little when someone comes up with a hypothesis then develops a mathematical model that supports that hypothesis. Not that it means this scientist, or any other is wrong, it’s just something to raise an eyebrow at.

    Hopefully other scientists will do their best to shot his model full of holes. If they fail, that would be cool. I like this idea, that somewhere out there is a piece of us wandering around.

    Could it have been taken in by another star after we so heartlessly kicked it to the curb?

  31. mfumbesi

    Oh My, Jupiter gets blamed for everything these day. I feel sorry for him. He must be denying it at the top of his lungs by now…….

  32. @22 MTU: Forty odd times seems unlikely unless it was somehow much closer to the Galactic Centre in a much smaller galactic orbit.

    Hah, you got me! I just stopped and thought about it – I thought that we orbited roughly every 100 million years. But I just realized that I got that number from the “Galaxy Song” from that movie “The Meaning of Life.” And now I realize that I didn’t even remember the song right: it was actually 200 million years. :-P
    That’s what I get for relying on Monty Python lyrics for my science trivia.
    And for trusting myself to remember them correctly :D

  33. @29 Vince RN: Hopefully other scientists will do their best to shot his model full of holes. If they fail, that would be cool. I like this idea, that somewhere out there is a piece of us wandering around.

    How do I shot holes? :D Seriously though, it does at least seem plausible in light of that recent study positing that there may be twice as many “rogue” planets as stars in the galaxy. Assuming the sun has an average or greater then average number of planets, you’d almost expect a planet to be ejected at some point.

    Could it have been taken in by another star after we so heartlessly kicked it to the curb?

    Someone can correct me on this, hopefully, but I was under the impression that for a body to be captured by another, it has to lose energy to a third body. That’d mean it wouldn’t just need to pass close to a star, it’d need to pass close enough to a planet orbiting that star to transfer at least enough velocity to enter a highly elliptical long-period orbit (that might be circularized later).

  34. CR

    @ 33 Joseph G…

    So much for my planet swapping idea… I think there’d be a lot of messed up solar systems based upon that.

    Of course, in a way, there are. Seems that there are so many systems we’ve found that don’t match what we thought we knew about how systems ‘should’ look, like gas giants really close to their stars, and so on. Maybe that’s why? Hmm…

    OK, I’m still thinking this is more sf than reality, but it’s late, I’m tired, and I just thought I’d throw that out there. Since we’re all speculating and all.

  35. ABC Dário

    Aaaand cue the Nibiru fanatics in 5, 4, 3…

  36. OneofNone

    @14 Joseph G: As I understand it the concept of escape velocity is different.

    This is defined as the minimum speed (i.e. kinetic energy) you need to never stop and return to the source of gravity where you escape from. But if you get farther and farther from that source, you get slower and slower. Toss your ball upwards from earth to see the concept. Tossed with exactly earth escape velocity, it will come to a standstill in infinite distance.

    So when this Planet X (hey, it is number 10) arrives at about 2 light year distance, it can be really slow relative to the sun. So basically it can orbit the galaxy in about the same time as the sun does, and by chance still be our neighbor.

    BTW: I suggest to name this Planet ‘Rupert’.

  37. Messier Tidy Upper

    @34. CR :

    So much for my planet swapping idea… I think there’d be a lot of messed up solar systems based upon that. Of course, in a way, there are. Seems that there are so many systems we’ve found that don’t match what we thought we knew about how systems ‘should’ look, like gas giants really close to their stars, and so on. Maybe that’s why? Hmm…

    I wonder if they’ve modelled other strange and messed up exoplanetary systems – such as the hyper-tilted orbit of Upsilon Andromedae d :

    http://blogs.discovermagazine.com/badastronomy/2010/05/24/nearby-planetary-system-is-seriously-screwed-up/

    the wrong way planets like XO 3 :

    http://kencroswell.com/WrongWayPlanets.html

    or the tight packed “asteroid belt of gas giants” around Kepler 11 :

    http://blogs.discovermagazine.com/badastronomy/2011/02/02/kepler-finds-a-mini-solar-system/

    to see if the model can, um, model them as successfully with the right data too?

    IOW given the specific info does this model work elsewhere in coming up with the solar systems we see or not?

  38. Messier Tidy Upper

    @25. Infinite123Lifer : “Here’s to you hypothetical planet!”

    Raises glass to that & drinks. :-)

    @26. amphiox : “Sneaky, Messier, sneaky. Smuggling in non-IAU usages of the term back into popular discourse like that.”

    Sneaky or straightforward? I’m entirely open and plain in my rejection of the IAU’s definition. I make no secret of the fact that I don’t agree with the IAU’s anti-Pluto definition, I won’t use it and I’ll call Pluto a planet – and Eris, Sedna and the other ice dwarfs planets too – because that’s what they are.

    @32. Joseph G : No worries! I love that song too. :-)

  39. ceramicfundamentalist

    all this conversation about planets being ejected and captured makes me wonder what is the possiblity that one of the current solar system planets originated somewhere else.

  40. Messier Tidy Upper

    @ ^ ceramicfundamentalist : Very remote indeed I think.

    Just because space is BIG, really, really big. Remember the Douglas Adams quote on that?

    Mind you, I could be mistaken and would be delighted to find out I was on this question.

    FWIW, I think I vagely recall reading somewhere that there was speculation that Sedna or maybe “Buffy”+ was possibly captured from another star system. Anyone else remember more about that?

    *****

    I wonder if the Missing Planet – our mysterious ejected fifth gas giant – could have had and kept moons?

    Say, a Europa-like moon that is tidally heated and, like Europa, perhaps an abode of life? Even when its wandering with its castaway Neptune a rogue world deep in the Black?

    Or would this world’s violent ejection and departure into the outer Darkness waay beyond our Sun have stripped it of any possible moons and rings?

    I wonder if we can work out what it probably looks like now if it even exists?

    *****

    + aka 2004 XR190 – Most “tilted” or highly inclined object travelling more “Up & down” than “left to right” with its inclination of 47 degrees – but in an unusually circular orbit. A scattered or detached disk object discovered in Dec. 2004 “Buffy” is the 6th most distant object so far known after Eris, Sedna and some unnamed TNO’s with an orbital range of 52 -62 AU currently its about 58 AU from our Sun.

  41. Gary Ansorge

    14. Joseph G

    So , how many Km are there in a light year again? Let’s see;

    1)there are 3600 seconds in one hour
    2)there are

  42. Gary Ansorge

    Oops,,,never mind,,,need,,, more,,,coffee,,,

  43. Gary Ansorge

    Oh well, the one thing to remember is,,,there are likely billions of wanderers in this galaxy. If one were to wander thru this solar system, it might play havoc with our planetary orbits but the effects would take centuries to have an impact on us. I hope our descendants would have the tech to outrun those effects,,,

    Gary 7

  44. I read Alan Boyle’s take on this – thanks for the think.

    I am confused, however, by the argument that Jupiter’s moving would have disrupted the inner solar system thus possibly having Earth crash into Venus and Mars (which clearly has not happened). Isn’t one of the strongest theories we have right now for the formation of our Moon that a Mars-sized object collided with the Earth? Is this not the type of chaotic inner-solar system behavior predicted by the movement of Jupiter?

  45. Steve Star

    Phil, would you mind doing a review of the new Lars von Trier film, “Melancholia”. It’s got stunning visuals, but I’m not sure how accurate the science is. Accurate or not, I thought the movie was amazing.

  46. icemith

    @39. ceramicfundamentalist Says:

    “all this conversation about planets being ejected and captured makes me wonder what is the possib(i)lity that one of the current solar system planets originated somewhere else.”

    Umm.. I’m surprised no one has ventured that WE , The Earth, may have been that planet, captured by the Sun, or if you prefer, Sol, and our step-sun has looked after us ever since. However, I don’t say that we, or our primordial ancestors were stowaways, just that with a stable environment, the conditions were “right” for our development, but that could have happened elsewhere anyway, and maybe often.

    (sorry for the slight correction, which I missed on reading the original, but my spell-checker picked it up when I copy/pasted the quote.)

    Ivan.

  47. Dan

    Seems to me the illustration with this article is inaccurate. If the planet were in interstellar space, it wouldn’t be close enough to the sun or any other star to reflect enough light to be seen. It would be completely dark.

    Obviously, I realize this is artistic license, but wanted to see if others agreed.

  48. Anchor

    #47Dan says, “If the planet were in interstellar space, it wouldn’t be close enough to the sun or any other star to reflect enough light to be seen. It would be completely dark.”

    No it wouldn’t. I vividly recall seeing my faint but quite obvious shadow on the ground one Summer night years ago while observing in the Mohave Desert. In the sky the only light source that was present that can have cast my shadow was the Milky Way in Sagitarrius. That’s right: I had seen a shadow cast exclusively by starlight other than the Sun! (The Milky Way that night was spectacular).

    Besides, “accuracy” isn’t just about making “artistic license” excuses. It’s perfectly conceivable that creatures with much larger-aperture and sensitive eyes than ours perceive the night sky much better than we do. Owls, for example, undoubtedly do. And it’s perfectly kosher to speculate (accurately!) about possibilities like extra-terrestrials or even intelligent interstellar space-farers, for example, somewhere Out There who may have evolved or engineered themselves eyes a meter or more across, optimized for interstellar light-levels. Our puny eyes are basically optimized for full terrestrial daylight conditions, which makes us nearly blind at night. So, as long as the artwork isn’t excessively fanciful (i.e., no dragons in sight) it’s less a question of ‘accuracy’ or ‘artistic license’ than it is of adjustment or calibrated perception. Even a camera’s long time-exposure reveals a reality we shall never witness with ‘our own eyes’.

  49. Georgijs P

    This reminds me of the Discovery’s documentary How the Universe Works episode about Solar Systems. It was said that it is possible that a gas giant has smashed into the Sun because in the Sun there was found a lot of element lithium witch is mostly found in gas planets and not stars. It might be possible but i can’t tell.

  50. Tezcatlipoca

    I think the truly Earth shattering point is being missed in all this. What does this mean for the “science” of Astrology? ZOMG! ;)

  51. Anchor

    @#26 amphiox says, “I suppose if it was ejected towards the galactic core, it could have fallen into a highly elliptical orbit which overall would have been much shorter than the solar system’s own orbit, allowing it to get forty odd revolutions in?”

    Nonsense. That supposes it was ejected with enough EXTRA speed to cancel a substantial part of the Sun’s orbital speed around the galaxy, which is just as hard as boosting it to galactic escape velocity from the Sun’s orbital distance from the center. (Square root of 2 x circular orbital velocity in the prograde direction gives you escape; to achieve a significantly elliptical orbit, that extra delta V has to be applied in the retrograde direction [NOT toward or away from the core!] but to cancel ALL of the circular velocity is harder than escape…and if a planet is ejected at just above Solar escape velocity in a random direction, it is very unlikely it’s going to do more than drift away gradually).

    The Sun’s motion around the galaxy – like that of every other star – isn’t repetitiously neat and Keplerian, but it doesn’t matter. The Sun has remained a resident disk star since its formation in the disk, and it has basically retained that momentum since its birth and has plied a ‘doodle trajectory’ (that also ‘bobs’ up and down out of the plane of the disk) – but of a fairly constant distance from the galaxy’s center, probably, within a factor of 2.

  52. Ken

    amphiox @26: The IAU definition doesn’t work, obviously, for planetary systems that are still in their early formation periods.

    Does that mean Pluto is still a planet if we define “early formation period” as “five billion years”? Or perhaps that Pluto could promote itself to planet if it cleared its orbit (which it won’t, but let’s pretend).

    Kidding aside, you just made me realize that the IAU definition is a dynamic one. Every current planet gained that status sometime in the past; and any of them could lose it, if some event re-cluttered its orbit.

  53. amphiox

    Does that mean Pluto is still a planet if we define “early formation period” as “five billion years”? Or perhaps that Pluto could promote itself to planet if it cleared its orbit (which it won’t, but let’s pretend).

    Perhaps an advanced future civilization harboring a deep cultural abhorrence for the IAU definition, could go into the Kuiper Belt and blow up/tow away/boost to solar escape velocity/drop into the sun/etc every single KBO except for Pluto, and thus TURN Pluto into a planet!

    (Or mine them all away for water and other resources, but leave Pluto untouched as a historical heritage site

    Kidding aside, you just made me realize that the IAU definition is a dynamic one. Every current planet gained that status sometime in the past; and any of them could lose it, if some event re-cluttered its orbit.

    Pretty much true for all our definitions, or course. We could call them proto-planets, just as we have a name for proto-star.

    (And if something recluttered the orbit of a current planet, that planet would eventually be able to re-clear it, leaving us with the situation of the planets losing and regaining its status, perhaps several times….)

  54. 35. @ABC Dário “Aaaand cue the Nibiru fanatics in 5, 4, 3…”

    FTW!

  55. Infinite123Lifer

    To continue the silliness @ 25

    Rupert! Get your gaseous arse back here right this second!

  56. Joseph G

    @34 CR: So much for my planet swapping idea… I think there’d be a lot of messed up solar systems based upon that.

    Of course, in a way, there are. Seems that there are so many systems we’ve found that don’t match what we thought we knew about how systems ‘should’ look, like gas giants really close to their stars, and so on. Maybe that’s why? Hmm…

    Planet Swap – that’d make a great reality show :D
    Seriously though, I do recall reading that most scientists don’t believe gas giants can form close to their primary, so the “hot Jupiters” we see must have migrated there. In order for a large planet to “fall” that close to its star, it’d need to lose a great deal of orbital energy. That energy has to go somewhere…

    @36 OneofNone: @14 Joseph G: As I understand it the concept of escape velocity is different.

    This is defined as the minimum speed (i.e. kinetic energy) you need to never stop and return to the source of gravity where you escape from. But if you get farther and farther from that source, you get slower and slower. Toss your ball upwards from earth to see the concept. Tossed with exactly earth escape velocity, it will come to a standstill in infinite distance.

    So when this Planet X (hey, it is number 10) arrives at about 2 light year distance, it can be really slow relative to the sun. So basically it can orbit the galaxy in about the same time as the sun does, and by chance still be our neighbor.

    BTW: I suggest to name this Planet ‘Rupert’.

    D’oh! *facepalm* You’re right, of course. Escape velocity has nothing to do with the eventual velocity of the object. My bad :)

  57. Joseph G

    @53 amphiox: Perhaps an advanced future civilization harboring a deep cultural abhorrence for the IAU definition, could go into the Kuiper Belt and blow up/tow away/boost to solar escape velocity/drop into the sun/etc every single KBO except for Pluto, and thus TURN Pluto into a planet!

    Shoot, why not just tow them to Pluto? Drop KBOs on Pluto until its mass is greater then the Earth’s. Lets see ‘em call it a “dwarf planet” THEN :D

  58. Steven S

    It didn’t get ejected by Jupiter, it got REJECTED.

  59. Infinite123Lifer

    Doh!, stop naming the hypothetical planet folks, my OCD is winning.
    Once again, continuing the silliness @25 & @55.

    Planet X, can you hear me? X? If your listening I want you to know something. . . your real name is. . .

  60. @45. Steve Star :

    Phil, would you mind doing a review of the new Lars von Trier film, “Melancholia”. It’s got stunning visuals, but I’m not sure how accurate the science is. Accurate or not, I thought the movie was amazing.

    The BA’s done that already – click on my name for link or cut’n’paste :

    Melancholia

    into the search box here. Posted July 10th, 2011 7:00 AM here by the BA.

  61. "Helen"

    Hi to everyone… Is it true that another “Earth-like” planet had replaced Jupiter? This is now the major talk in our community, especially in school… I just surprised to see the word “EARTH-LIKE” and if it is true, I ‘d consider it to be one of the greatest gifts God had given for us! Imagining in the future, a new Home where we might live…

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »