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Space Science

Solar Systems Like Ours Are Likely To Be Rare 394

KentuckyFC writes "Astronomers have discovered some 250 planetary systems beyond our own, many of them with curious properties. In particular, our theories of planet formation are challenged by 'hot Jupiters,' gas giants that orbit close to their parent stars. Current thinking is that gas giants can only form far away from stars because gas and dust simply gets blown away from the inner regions. Now astronomers have used computer simulations of the way planetary systems form to understand what is going on (abstract). It looks as if gas giants often form a long way from stars and then migrate inwards. That has implications for us: a migrating gas giant sweeps away all in its path, including rocky planets in the habitable zone. And that means that solar systems like ours are likely to be rare."
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Solar Systems Like Ours Are Likely To Be Rare

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  • by BigDaddyOttawa ( 948206 ) on Wednesday August 13, 2008 @10:58AM (#24583567) Homepage
    Get Bruce Willis on the phone, time to go "Armageddon" on Jupiter's ass.
    • Get Bruce Willis on the phone, time to go "Armageddon" on Jupiter's ass.

      Haha. I don't know about sending Bruce WIllis, but this does make me wonder why we have never (to my knowledge...) sent a probe INTO one of the gas giants. We have done flybys and taken photos etc. but it should prove interesting to send cameras and other instruments directly inside one of them. Maybe we could determine whether there exists a solid surface or core underneath the gases (and if it's something exotic like metallic hydrogen) and get an idea of why some of them radiate more heat than they re

  • Rare? (Score:5, Insightful)

    by east coast ( 590680 ) on Wednesday August 13, 2008 @10:59AM (#24583569)
    I didn't RTFA, but I will when I get home.

    But on the surface it seems more to me that they're just saying that solar systems have a life cycle that is marked by the location of gas giants. I don't really think that means that our setup is rare.

    But if I am misinterpreting the blurb and that is what they're proposing I would still say we need to hold our horses on any real judgement. We've found these solar systems because our current method of seeking these solar systems out is going to be more likely to find this kind of activity as opposed to what we have here at home. I think we're jumping the gun a bit on this one. I say let them work it out for a couple of more decades and even then we should be a bit more cautious about such sweeping statements.
    • Re:Rare? (Score:5, Insightful)

      by dintech ( 998802 ) on Wednesday August 13, 2008 @11:02AM (#24583609)
      I agree. In addition, 250 systems really isn't a lot. I'm just a lay-person but it occurs to me that the easiest ones to examine via red-shift are those with a gas giant close to the sun.
      • Re:Rare? (Score:5, Informative)

        by mapsjanhere ( 1130359 ) on Wednesday August 13, 2008 @11:47AM (#24584463)
        The method used to find these systems are changes in the star's brightness when the planet passes in front of the star - so systems with large planets in close orbit are the ones to be noticed first. If you have a planet like Jupiter with an orbital period of around 12 years, you're much less likely to catch that event compared to those "unexpected" systems with short periods.
      • Re:Rare? (Score:5, Insightful)

        by shma ( 863063 ) on Wednesday August 13, 2008 @12:02PM (#24584731)
        The parent is correct that there is a selection bias in our detection methods of planets that favours systems with gas giants close to the sun. However, this has nothing to do with the conclusions of the article. What they are saying is that, initially, the discovery of so many closely orbiting gas giants was confusing given that their models of planet formation show gas giants developing far away from the sun. What they have found through simulations is that gas giants naturally migrate inwards as the solar system evolves. So a 4 billion year old system like ours with gas giants far from the sun in unlikely. This conclusion comes from the simulations of solar system evolution, not from the observational data.
    • I agree, how many known galaxies are there? More than 100 billion (according to Wikipedia*) and with some having as many as one trillion stars (according to Wikipedia*), I'd say the chances of a star system being similar to ours is very possible. Same goes for life, intelligent or not.

      *It's on Wikipedia, it must be true

      • Re:Rare? (Score:5, Informative)

        by CastrTroy ( 595695 ) on Wednesday August 13, 2008 @11:27AM (#24584061) Homepage
        But that doesn't make them not rare. If there's 100 billion star systems, and even just 1 million stars in each, you are looking at 100,000,000,000,000 star systems. Even if there is a .000001% chance of a star system like ours existing, it means that there are 1,000,000 star systems that are like ours. So they could be both very rare, and yet still very likely to happen.
        • by Cheeko ( 165493 )

          "There are 400 billion stars out there in our galaxy alone. Now if only one out of a million of those stars had planets. Alright? And if just one out of a million of those had life. And if just one out of a million of those had intelligent lifeâ¦there would be literally millions of civilizations out there."

          Sure maybe you have to shift a few decimal places, but rare, still isn't necessarily rare.

          Then again, if its RARER, than we expect, what are the odds of finding it in any sort of appreciable tim

        • Re:Rare? (Score:5, Interesting)

          by Hektor_Troy ( 262592 ) on Wednesday August 13, 2008 @12:16PM (#24584949)

          That's still rare. If we assume that there's 100 billion galaxies in the world (which Wiki says is the current estimate), and put a star system like ours on the rare end of the scale as in 1 per galaxy, you do end up with 100 billion star systems like ours. But that's still extremely rare, as it's pretty much impossible to find one.

          Look at it another way: In 2006 the world supply of platinium was about 217,000 kg. That's about 1,112,341 mole or 667,404,810,235,590,822,414,959,709,663 molecules. That's a BIG number, but it's still a very rare metal. So rare in fact, that 2006 world supply wouldn't even let you give 1 gram of platinum to each resident of the United States.

          Big numbers doesn't indicate how rare something is. Rare is an indication of the chance/risk of encountering something. And in a huge universe with 100 billion galaxies, 100 billion star systems like ours is RARE! In fact it's so rare, that it might as well not exist anywhere else, because without visiting other galaxies, we'd never know they were there.

        • Re: (Score:3, Informative)

          by Teancum ( 67324 )

          What this does do, in terms of some realistic statistical calculations in regards to earth-like planets, is to adjust the Drake Equation [] downward by reducing statistically the number of potential planets that might be capable of supporting carbon-based life in aqueous solutions.

          This paper is significant so far as to reduce the potential number of planets possible by a couple orders of magnitude.

          Yeah, out of the billions of stars in our galaxy and out of the billions of galaxies in our universe, this still m

    • by 4D6963 ( 933028 )

      Exactly, because of the type of system we find is quite particular (i.e. gas giant near its star, the bigger the star the closer and bigger the planet) this conclusion may apply only to a few categories of planetary systems. By the way, isn't the consensus on the formation of the solar system that our gas giants moved away from the Sun?

    • Re:Rare? (Score:4, Insightful)

      by Devout_IPUite ( 1284636 ) on Wednesday August 13, 2008 @11:27AM (#24584087)

      A man drove from the Dallas to Phoenix.

      Upon arriving in Phoenix he casually remarked to a gas station attendant "It's a sham about everyone leaving Phoenix, it's such a nice place."

      Confused, the gas station attendant asked "What do you mean sir? Why would everyone be leaving Phoenix?"

      Tthe man confidently replied "On my way to Phoenix I saw way more people heading towards Dallas from Phoenix than going to Phoenix from Dallas! I'd say it must be fifty to one of people leaving Phoenix."

      The gas station attendant didn't say anything, but we all knew what he was thinkings... 'Of course you saw more people going the opposite way while you drove you idiot! Your relative speeds much closer and you only see new people when someone passes or turns, you see everyone in the other lane on the other hand'

  • wake me up (Score:4, Insightful)

    by ionix5891 ( 1228718 ) on Wednesday August 13, 2008 @11:02AM (#24583625)

    when they have capability of detecting Earth > Venus > Mars size planets

    they don't have much data do they to base their theory on?

    • Re: (Score:3, Informative)

      by RogerWilco ( 99615 )

      The point is not about being able to detect rocky planets. It is that according to the old models a gas giant close to a star could not exist. We now found 250 of these impossible planets, so after adjusting the theory so these are possible, we find that rocky inner planets are all of a sudden a lot less likely.

  • gas giants? (Score:4, Interesting)

    by greenguy ( 162630 ) <estebandido&gmail,com> on Wednesday August 13, 2008 @11:02AM (#24583627) Homepage Journal

    If gas and dust get blown away, what's to say that rocky planets weren't originally gas giants? It could be that the gases were (mostly) stripped away, leaving the core. Perhaps our rocky planets formed further out, migrated in, but found steady orbits as they lost mass.

  • giants (Score:4, Interesting)

    by Anonymous Coward on Wednesday August 13, 2008 @11:03AM (#24583635)
    I thought it was commonly understood that for a solar system like ours to exist, that there needs to be a gas giant to act as a "protector" for the habitable planet(s). That is, the larger planet acts as a gravity well to lure some of the larger objects that could collide into the habitable planet. From the summary, it merely seems to be saying that the gas giant forms closer to the star than originally thought, but that it migrates outwards later in its life and helps to clear a zone for the habitable planet to exist.
    • Re: (Score:3, Informative)

      by Tubal-Cain ( 1289912 )

      Other way around. They are saying that gas giants form far away and move inward.

    • Re: (Score:3, Informative)

      by sm62704 ( 957197 )

      I saw AFA on this a couple of days ago. They're not referring to observed star systems; we can't yet detect earth sized (or earth massed) planets yet.

      They ran a computer simulation of star formation and the simulations had gas giants migrating inward, which ate rocky planets like ours. It is yet to be determined how accurate the simulations are.

  • But... ?? (Score:3, Funny)

    by mmu_man ( 107529 ) on Wednesday August 13, 2008 @11:04AM (#24583643)

    I know there are many solar systems with inhabitable planets in the galaxy and others, I know it!
    I've seen the documentary on TV!
    What was it called... hmm Stargate, yes, that's it!
    And the Ancients seeded life over all of them, they said so in Stargate Atlantis!
    I suppose they didn't watch TV enough to have missed such a proof.

    • I saw that documentary too. IIRC, there were a finite number of inhabitable worlds, maybe a few thousand (not sure they actually ever told us). This could still mean that the habitable planets are rare, just that all of them are colonized by humans.
  • Sweeping out Earths (Score:4, Interesting)

    by xZgf6xHx2uhoAj9D ( 1160707 ) on Wednesday August 13, 2008 @11:04AM (#24583651)

    I can't follow 100% the article, so hopefully someone can clarify this point of curiosity for me.

    Is one of the implications that solar systems could at one point be similar to ours? Gas giants far away with smaller planets towards the sun? And then the gas giants slowly creep towards the sun, wiping out the smaller planets that get in the way?

    • by Rob Kaper ( 5960 ) on Wednesday August 13, 2008 @11:12AM (#24583773) Homepage

      Is one of the implications that solar systems could at one point be similar to ours? Gas giants far away with smaller planets towards the sun? And then the gas giants slowly creep towards the sun, wiping out the smaller planets that get in the way?

      That's a possibility, although I would turn around your phrasing: our solar system could at one point be like the ones we're detecting far away, with Jupiter sweeping away Earth and our small neighbourhood friends.

  • by laggist ( 784355 ) on Wednesday August 13, 2008 @11:06AM (#24583691)
    ... or should I start welcoming our Jovian overlords?
    • Re: (Score:2, Interesting)

      by mmu_man ( 107529 )

      I was just wondering that.
      We know the moon is getting further 3,8 cm per year, but we don't yet have any other such measurement for our neighbours.
      Though it's harder putting a reflector on the surface of jupiter :)
      How about Mars btw ?
      In any case, it shouldn't happen for the next million year unless Bender's friends do fart too much all in one direction ;)

    • If you're wondering if Earth is going flying into space during the lifespan of our species... probably not. But over the lifespan of the Sun... there's a good chance that one or more of the inner planets is in trouble before the Sun goes nova.
      • Re: (Score:3, Informative)

        by MBGMorden ( 803437 )

        here's a good chance that one or more of the inner planets is in trouble before the Sun goes nova.

        A nova is caused when a white dwarf star accrets a significant amount of mass from a neighboring body. Our Sun will end up as a white dwarf, but without a companion of any significant size, it is high unlikely that it will ever go nova.

        It's also not massive enough to go supernova. So basically, the Sun is simply not likely to ever explode in any way. Eventually it'll swell into a red giant and after that it'll mostly start to slowly dissolve it's outer layers. It'll go out with more of a fizzle than a b

  • by SengirV ( 203400 ) on Wednesday August 13, 2008 @11:08AM (#24583717)

    "... Everything looks like a nail" situation to me. We've only really had the ability to discover LARGE planets around solar systems. Also, the shorter the orbit period, the easier it is to detect.

    So logically, the planets we've found to date look NOTHING like those of our solar system. Jupiter's orbital period is 4332.71 days!!! And we are comparing that to the VAST majority of discovered planets(hot Jupiters) with orbital periods of less than 10 days?

    Seems like this article belongs in the "Are US Voters Informed Enough About Science?" thread if you ask me.

    • Re: (Score:2, Insightful)

      by Yvanhoe ( 564877 )
      Do you honestly believe they didn't take that factor into account ?
      Astronomers would be the firsts to enjoy a theory that says that We Are Not Likely To Be Alone. Be sure that if this discovery is peer-reviewed, all these arguments have already been opposed.
    • As it would to me.

      The problem with these sort of assessments, particularly when it comes to understanding the universe around us at that scale, is that we are constantly working with what little "facts" that we have.

      I am not saying that we should not be constantly guessing how the universe interacts around us, only that we take it with a grain of salt and think critically.

      Essentially the less we know the more wild our guesses. The more assumptions that have to be made the the less likely whatever we come up

    • Re: (Score:3, Insightful)

      by Jerf ( 17166 )

      This is a big deal, because back when we only knew about our solar system, we formed theories to explain it. These theories imply that we wouldn't find many cases of large gas giants near suns. The current observations falsify these theories. We don't have to have a total picture of every planet in the vicinity to know that; detecting too many large planets is sufficient.

      Your issue of our ability to detect only these types of planets is totally irrelevant to the main point about our theories making now-fals

      • by SengirV ( 203400 ) on Wednesday August 13, 2008 @12:18PM (#24584977)

        Yes, our theories were WAY off. No one predicted that these hot Jupiters were out there. Now they make up almost all of the planets we've detected to date. The point I was trying to make is that we can't detect solar systems like ours yet. Unless MAYBE it was in the alpha centaurus system and then MAYBE if it's Jupiter equivalent were to pass in front of one of the stars.

        Please, tell me how many exosolar planets we've found with orbital periods greater than 365 days? How about 4000+ days like Jupiter?

        Talking about how rare we are, without even another example, because we lack the ability, is just another theory that will fall - kinda like the planet formation theories that lacked the ability to predict "hot Jupiters". Now they have gone to the other extreme and theorized that EVERY solar system starts out with hot Jupiters. You know, because that is all we can presently detect.

        How is that irrelevant? It's EXACTLY the "To a hammer, all looks like a nail" analogy I started with. Since that is all we have the ability to find at present, now all solar systems must start out that way?!?!?!?

        This is the same mistake all the theorists made to start with, since all we had was our own solar system to base this upon. Now they have gone exactly the opposite way in their theories which is repeating the same mistake they initially made.

        Yes, you adapt your theories based upon more and more observational data. But when you KNOW your observational data is limited to one subset of possible outcomes(which makes our own solar system damn near impossible to form) and you claim "victory", that's just very illogical to me.

    • Re: (Score:2, Informative)

      by sm62704 ( 957197 )

      Seems like this article belongs in the "Are US Voters Informed Enough About Science?" thread if you ask me.

      If you're an American then you made your own point. TFA isn't talking about observation, but theory and computer simulation.

  • Let's wait for another millennium before we jump to the answer.
  • Hmmm (Score:5, Interesting)

    by tgd ( 2822 ) on Wednesday August 13, 2008 @11:15AM (#24583817)

    Even if solar systems configured like ours are rare, it doesn't suggest that is a problem for either the development of life or intelligence as we'd recognize it (and really is no problem for any other forms of "life").

    A gas giant in the "habitable" zone may have multiple moons that end up habitable. If Jupiter was in Earth's orbit its entirely possible 2-3 or more of its moons would be habitable in some form.

    That both increases the odds by having more places habitable, but increases the possibility of panspermia, so you could actually have greater diversity in that situation.

    • This is one of two truly insightful comments in the entire thread. The other post is about how gas giants that wander towards the star might have their gasses blown away by the star over time, and leave only the core.

      Just because the configuration of a star system isn't exactly like ours, doesn't mean it can't support life. Our gas giants have a multitude of moons, many of whom are very close to Earth in composition. And it's not like gas giants suddenly up and leave their moons behind when they head toward

      • Re: (Score:3, Interesting)

        by MBGMorden ( 803437 )

        but that doesn't mean new complex life wouldn't arise afterwards once the gas giant settles into a stable orbit.

        That comment got me thinking - generally once something starts in a certain direction it will not change unless something affects it. Any gas giant that formed further out and drifted in obviously was not in a stable orbit to begin with - so what would ever stabilize it? It seems like EVENTUALLY these drifting planets would in all likelihood drift into their parent stars. Maybe we're really detecting these planets in their "final days" (on a cosmic timescale) before they go crashing in?

  • What should I be most afraid of, earth swallowed by a dying sun or swallowed by a wandering jupiter?

  • by speedtux ( 1307149 ) on Wednesday August 13, 2008 @11:16AM (#24583853)

    Actual data is highly biased towards gas giants in close orbits because that's what's easy to detect.

    Simulations like these don't have sufficient real-world data to make any reasonable statements about what kinds of solar systems are likely.

    Also, "rare" is a relative term; if 1% of all planetary systems contain a habitable planet, there would be a lot of them and they'd be rather closely spaced.

    • Also, "rare" is a relative term; if 1% of all planetary systems contain a habitable planet, there would be a lot of them and they'd be rather closely spaced.

      Very true. Also, keep in mind that the chance of it being "habitable" is actually higher than most people might think. For example, our solar system has at least three strong possibilities for places that harbor or at one point harbored life: Earth, Mars, and Europa.

      Of course, the real issue here is that even the distance to our nearest neighbo
  • The reason we see so many hot Jupiters is because, having large masses and being close to their parents, they are by far the easiest planets to detect.

    We won't be able to draw any real conclusions about other solar systems for quite some time yet.

  • by IronClad ( 114176 ) on Wednesday August 13, 2008 @11:25AM (#24584031) Homepage

    Are you suggesting that Jupiters migrate?


  • Isn't this conclusion mainly inferred from our means of detection?

    We most easily detect planetary systems with a big wobble due to a gas giant near the star, so those are the ones we see, and from that we conclude that most planetary systems have a gas giant near the star. Whoa.

  • by webrunner ( 108849 ) on Wednesday August 13, 2008 @11:41AM (#24584321) Homepage Journal

    Really, in terms of the universe, EVERYTHING is rare. Galaxies are rare. Stars are rare. Matter is rare. About the only thing that isn't rare is space itself. Draw a line segment across the universe, make it trillions of miles long. How many atoms did you actually touch with that line?

  • I'll have you know that I have a nice summer home on the Red Spot of Jupiter and have lived there happily for quite some time so anytime you feel like dying please do drop by.

  • by Geoffrey.landis ( 926948 ) on Wednesday August 13, 2008 @11:56AM (#24584601) Homepage
    The data set seems a little biased.

    The interesting data is not how many hot Jupiters are found, but how many stars do not have hot Jupiters.

    Here's a list of extrasolar planets [] (last updated in January); and another list []. Note the large number of stars that have planets found with mass less than Mj. The converse of that is that those stars do not have planets of mass greater than Mj. The problem, of course, is that negative results are much less published than positive results. However, here is a list of three published papers that listed stars with no planets found [] (that is, no planets large enough to detect-- which is to say, no hot Jupiters. This list is somewhat out of date, as of 2006.)

    So the story is a little incomplete. Some solar systems have hot Jupiters, which in their migration inward disrupt smaller, earthlink planets... but by no means all.

  • by AbsoluteXyro ( 1048620 ) on Wednesday August 13, 2008 @11:59AM (#24584663)
    Best estimates put us at 30 billion planetary systems in the Milky Way galaxy alone. If only 0.0001% of those planetary systems holds an Earth-like planet capable of sustaining life, that's 3 million Earths, just in the Milky Way. Now consider that figure holds for all galaxies. A conservative estimate from Nasa's scientists puts the universe at 125 billion galaxies. That's 3 trillion 750 billion planetary systems. If only 0.0001% of those systems are host to life-sustaining Earth-like worlds, that's 375 billion Earths in the universe. Perhaps that is rare, considering how stupidly big our universe is... but that is still a hell of a lot of Earths.
  • how many stars are in the Milky Way? 200 billion? So, if only one in a million produces an Earth like planet, then there are 200,000 Earth like planets in the Milky Way.

    Not that it matters since there is no way for us to get to, or communicate with, even the nearest stars.... right now.

  • by dtolman ( 688781 ) <> on Wednesday August 13, 2008 @12:04PM (#24584759) Homepage

    These ideas aren't _directly_ coming from the admittedly biased detection of large gas giants with close in orbits. Everyone knows that the detection scheme we use is biased to find them, and it would be impossible to find many systems like ours using it. But that doesn't really matter at all. The very fact that Hot Jupiters exist at all, have big implications to how systems form.

    Finding these big planets close in meant that old planetary formation theories had to be revised. New theories, based off how these planets could form at all, state that planets don't form in place - they form farther out and migrate in. It also means the Solar System is lucky Jupiter stopped where it did - if it migrated further inwards all the planets in the inner solar system would've been flung into space...

  • Make Up Your Minds (Score:3, Insightful)

    by immcintosh ( 1089551 ) <slashdot.ianmcintosh@org> on Wednesday August 13, 2008 @12:07PM (#24584811) Homepage
    It seems like every other day there's a new article/paper/prognostication conclusively demonstrating the rarity/abundance of Earth-like planets/systems. Honestly, at this point I'm just going to hold my judgment until I can get out there and see for myself.
  • by Maury Markowitz ( 452832 ) on Wednesday August 13, 2008 @12:44PM (#24585495) Homepage

    Do you know why they though solar systems like ours would be common? Computer simulations of solar system formation. In fact, the "standard model" was even published in Creative Computing, back in the day...

    What were these models based on? The only example of a solar system we knew; our own. "Of course" there will be rocky planets near the sun and gas giants further out, it only makes sense.

    So then we get better telescopes that can detect Jupiter-sized planets, and they show us lots of systems with gas giants in close. The model, based on a single example, is wrong. So we re-jigger the model to match the new observations, and conclude THAT one must be right.

    $50 says once the interferometric planet finders come online this model goes into the trash heap as well. The universe clearly doesn't give a crap about our models, and builds whatever it wants.


  • by Angst Badger ( 8636 ) on Wednesday August 13, 2008 @01:09PM (#24585971)

    Hmm. Every time our knowledge of the universe expands, there is always a group of scientists who rush to say that the new evidence indicates that we are, in one way or another, the center of the universe. And when that conclusion is invalidated by still more new evidence, they go hunting for another reason to reinstate their conclusion. The "Rare Earth" faction is just the latest iteration of the same deep-seated emotional bias that gave us geocentrism.

    We have exactly one stellar system that we have studied in detail and exactly one example of a living ecosystem, and all our knowledge of other stellar systems comes from techniques that exclusively detect stellar systems with a massive planet in a tight orbit around its star. It seems to me that our sample size is too small to reach any conclusions at all, and until we have better tools for observing other stellar systems in high detail, discussions about what constitutes a "normal" stellar system barely rise above the level of pure speculation.

  • The logic (Score:3, Insightful)

    by krazytekn0 ( 1069802 ) on Wednesday August 13, 2008 @01:20PM (#24586173) Homepage Journal
    Doesn't seem to work out for me. Their logic is that star systems have a timeline related to gas giants, so star systems like ours are rare? I guess the problem here is the totally subjective word "rare" But I don't see how star systems nearly the same age as ours (far gas giants) can't be just as common as star systems that are older (near gas giants) So rare? probably, but same way you could say "people who live with their parents are rare, because when people get older they generally move out of their parents house" (and we're talking all people, not just adults)
  • by iamghetto ( 450099 ) on Wednesday August 13, 2008 @01:46PM (#24586699) Homepage

    But space, the planets and galaxy are too numerous to imagine. Basically infinite.

    Rare x Infinite = Infinite

    They might be thousands of lights years apart, but there are still billions of them.

  • All supposition (Score:4, Interesting)

    by jgoemat ( 565882 ) on Wednesday August 13, 2008 @04:34PM (#24589517)

    It wasn't 20 years ago when we hadn't detected another planet yet and we didn't know if planets formed around other stars. Now we know they are common, but the ones we detect are large and close to the sun. There's a reason for this: the method we use to detect extrasolar planets works by detecting the gravitational tug between the planet and star by the changing of the star's luminosity over time. If there's a 72 hour cycle where the star dims and brightens, then we know there is a planet in a 3-day orbit around the star. We know how far from the star it is by using the orbital period and the mass of the star. We know the mass by how much the star's luminosity is affected.

    There is noise in the observations caused by regular luminosity changes in the star, like from sunspots. The larger and closer the planet to the star, the bigger the change in luminosity and the easier it is to separate that signal from the noise. Also the closer planets give more data to work with. If the star has a 72 hour orbit, you will be able to see a complete cycle every three days. If the planet is like Jupiter, it could be 5 AU from the sun and have an orbital period of 12 years.

    Their entire reasoning appears to be based on the assumption that a body the size of these 'hot Jupiters' couldn't form that close to the star because the solar wind would drive the gas away. If that were truly the case, then a star couldn't form at all because the solar wind would drive all of its gases away. If the main gas for the planet accumulates prior to solar ignition then there isn't a problem. This new survey only looked for super-Jupiters that are 5 or more times the size of Jupiter, and that are twice as far away from their star as Jupiter is from Sol. The thing is that if a planet gets to be about 13 times the size of Jupiter then it starts to fuse deuterium and becomes a star. We have found many binary stars that would meet the criteria sought, but that don't count because the mass of the "planet" was too big and it became a star.

    These are great questions to ask, but I don't know why the media portrays it as such a surprise that things can be like our solar system. Is anyone really surprised that we found water on Mars? Earth has plentiful water, comets are mostly water, Cassini observed [] water geysers on Saturn's moon Enceladus. Water is simply the combination of the first and third most plentiful elements in our universe, and the second most plentiful element doesn't chemically bond. Water should be the most abundant molecule in the universe after H2.

    This article [] is a good example. It seems to claim that a solar system would need a planet like Jupiter for there to be life. In one paragraph they say that Jupiter prevents the inner planets from being bombarded by too many space rocks, and in the very next paragraph it says Jupiter perturbs the orbit of space rocks to make them hit Earth, seeding it with water and organic molecules. We don't know enough about formation of planetary systems to say that one would need a Jupiter-like planet for life to form. It sounds like the people that claimed 20 years ago that planetary systems would be very rare before we found our first extrasolar planet (we've found hundreds now).

    I'd like to see the whole paper and look at their models. I'd like to know what would cause a planet that formed over millions of years in the outer solar system to move in closer to the star. When it forms, it has an orbital velocity relative to the center of gravity of the system. In order to migrate closer to the star, some other massive object would have to slow it down, wouldn't it?

  • by PinchDuck ( 199974 ) on Wednesday August 13, 2008 @08:00PM (#24592377)

    which is then savagely generalized to come up with the unwarranted conclusion that systems like ours are rare. They've got 250 systems observed, wrote a model to match that observation, then decided that the computer model is now the new thinking behind planet formation. It's only a computer model, and we have billions of more datapoints to collect. It ain't time to generalize yet.

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