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Solar Systems Like Ours Are Likely To Be Rare
Posted by
CmdrTaco
on Wed Aug 13, 2008 09:52 AM
from the i-prefer-my-solar-system-medium-rare dept.
from the i-prefer-my-solar-system-medium-rare dept.
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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Well, that does it... (Score:5, Funny)
Re:Well, that does it... (Score:5, Funny)
On the other hand, the rest of us wish you'd learn to spell "probability".
Parent
Re:Well, that does it... (Score:5, Funny)
Maybe he should use a spell chequer!!
Parent
Re:Well, that does it... (Score:5, Insightful)
Whatever... this is naval gazing and conjecture, no more credible than Intelligent Design. These guys have a few data points, they create a highly convoluted system that seems to account for their data points, then the moment they get more data, they start over. Again and again.
A good critical thinker should know when to say "We don't have a fucking clue" if they want to be taken seriously. But then, it's all about money, isn't it?
Parent
Re:Well, that does it... (Score:5, Informative)
Whatever... this is naval gazing and conjecture, no more credible than Intelligent Design. These guys have a few data points, they create a highly convoluted system that seems to account for their data points, then the moment they get more data, they start over. Again and again.
Data points which are skewed by the fact that planets with a large mass (relative to the star) orbiting close to the star are easier to detect by techniques based on star wobble and transit light level and so are going to be massively over represented in the list of known planetary systems.
Parent
Re:Well, that does it... (Score:4, Funny)
# Watching the ships roll in
And I watch 'em roll away again
Sitting on the dock of the bay /#
Watching the tide roll away..
Parent
Re:Well, that does it... (Score:4, Interesting)
If you don't know the exact probability of something happening, you can attach a probability to the probability.
From science, suppose your hypothesis is that something is binomially distributed with p=0.5 (eg number of heads from fair coin flip). Suppose after 100 trials you find a number of heads that lead you to reject the hypothesis with p0.05. In that case, you would say:
I reject the null hypothesis with p0.05
In other words:
It is very unlikely that the null hypothesis is true
in other words:
It is very unlikely that the probability of getting a head is 0.5
In other words: if you have uncertain data about a probability, it is perfectly natural to state that some event has probability X with probability Y
Parent
Re:Well, that does it... (Score:5, Interesting)
I'm no expert, but as I recall the major problem with probes into the gas giants is that the immense pressure inside of them would crush anything we're capable of making, and electromagnetic interference from the constant storms would make it impossible to transmit any data out.
Plus, every time anyone mentions sending probes into Uranus over at NASA, nobody can stop giggling long enough to seriously work on the problem.
Parent
Re:Well, that does it... (Score:5, Informative)
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.
Your geek credits have been officially revoked.
Galileo had a probe that was dropped into the atmosphere of Jupiter and it transmitted data for 58 minutes [nasa.gov] before it stopped. Hell, we even crashed the Galileo spacecraft into Jupiter to prevent contaminating Europa or Callisto with organisms from Earth.
Parent
Re:Well, that does it... (Score:5, Informative)
We have.
in 1995 by the Galileo a probe was dropped into Jupiter.
http://apod.nasa.gov/apod/ap951207.html [nasa.gov]
But if you think it will just sink in until it 'hits' then check your physics on large gas giants again.
Parent
Rare? (Score:5, Insightful)
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)
Parent
Re:Rare? (Score:5, Informative)
Parent
Re:Rare? (Score:5, Insightful)
Parent
Re:Rare? (Score:4, Insightful)
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'
Parent
Re:Rare? (Score:5, Insightful)
They're not actually determining that solar systems like ours are rare from the observations. The observations were incompatible with our current thinking on solar system formation. Solar system formation was reexamined, and a more-accuracy theory of solar system formation suggests that systems like ours are unlikely.
Parent
Re:Rare? (Score:5, Funny)
Extensive computer simulation from basic principles. Not, "well, this theory more closely matches what we've recently observed, so it's more accurate".
Believe it or not, logical weaknesses that can be caught by the Slashdot crowd are almost always noticed by scientists. It's just that Slashdot doesn't read the articles.
Parent
Re:Rare? (Score:4, Insightful)
No, our old assumption was that people could not grow beyond 1m/3feet even as adults. We then started looking for them, and found lots of adults over this size. The scientists have adjusted their theory so that it can explain the existence of people over 1m/3feet is size.
The side effect of their model is that it also predicts that adult people under 1m are probably quite rare.
Parent
Re:Rare? (Score:5, Informative)
Parent
Re:Rare? (Score:5, Interesting)
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.
Parent
wake me up (Score:4, Insightful)
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:wake me up (Score:5, Informative)
That's Gliese 581c, which is merely five times the mass of the Earth --- and they only detected it because it orbits at one fourteenth of Earth's orbit. In other words, it's a heavy planet very, very close to its sun. The only reason it was described as 'Earth-like' is that Gliese 581 itself is a red dwarf, which means it's much cooler than Sol, which puts 581c in the star's life zone.
So, while it's theoretically possible that 581c could support life, it's still not really Earth-like. We're still a long way off from being able to detect Earth-sized planets at Earth-orbit distances from Sol-like stars.
Parent
gas giants? (Score:4, Interesting)
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)
Re: (Score:3, Informative)
Other way around. They are saying that gas giants form far away and move inward.
Re: (Score:3, Informative)
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)
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.
Sweeping out Earths (Score:4, Interesting)
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?
Re:Sweeping out Earths (Score:4, Informative)
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.
Parent
is Jupiter's orbit stable... (Score:3, Funny)
This appears to be a "When you are a hammer ..." (Score:5, Interesting)
"... 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:3, Insightful)
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
Re:This appears to be a "When you are a hammer ... (Score:5, Insightful)
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.
Parent
Hmmm (Score:5, Interesting)
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.
there's nothing there (Score:4, Insightful)
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.
The planets may seek warmer climes in winter.. (Score:5, Funny)
Are you suggesting that Jupiters migrate?
--
Incoming!
The universe is big. (Score:3, Insightful)
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?
It's not all hot Jupiters out there (Score:5, Informative)
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 [exoplanets.org] (last updated in January); and another list [exoplanet.eu]. 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 [exoplanet.eu] (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.
Depends on your Definition of Rare (Score:4, Insightful)
Other observational evidence (Score:4, Insightful)
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.
All supposition (Score:4, Interesting)
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 [msn.com] 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 [space.com] 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?
Re:first post (Score:5, Funny)
Nothing says "sanity" like a preemptive defense.
Parent
Calculating a planetary system. (Score:5, Interesting)
Personally I think it's hard to decide if our planetary system is rare or not just by computer simulations. There are too many factors involved to make it easy to calculate how a planetary system evolves.
There have been many guesses over the last century about how the planets did form. But from the data we now have from a few other planetary systems we can at least say that a few of them have large planets (gas or not remains to be seen).
And what would say that a planet has to be the size of earth to provide for life? A gas giant may be good for life too, but maybe not the life we know here.
Parent
Re:first post (Score:4, Funny)
The Electric Universe theory contradicts Time Cube theory, and thus cannot be valid, as Time Cube theory encompasses everything.
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Re:first post (Score:5, Informative)
Outsider theories always have the burden of proof on their own shoulders. To paraphrase someone famous, "there are many questions fools can ask that wise men struggle to answer." There's no where this applies more than in science. Creation Science can throw out some sticky questions and make some points that are hard to disprove.
But Science is about proving things, not suggesting every possible idea and disproving them one by one. For a well established idea that has made a lot of successful predictions, even a known incomplete idea like the standard cosmological model, to be tossed aside, there needs to be an overwhelming amount of evidence, not just some compelling questions.
If an alternative model of the universe explains the preponderance of evidence we already have (such as the background radiation, the count of galaxies, the scarcity of structures above a certain scale, the calculated mass of galaxies, the total amount of gamma radiation etc.) as well as a current theory, as well as making successful new predictions that existing models failed to make, then over a process of several years, people in the field would become convinced, and as the literature is peer reviewed, the dogma would shift. But established scientific ideas are SUPPOSED to be dogma. It isn't politics. Equal time isn't given to competing ideas, that's not the way it works. There are too many bad scientists and professional crackpots, the system would collapse without a hierarchy of opinion.
And all science works this way and always has. Even the sciences that cure disease and deliver technological miracles. Since those things keep happening, I'm confident as a semi lay person that science, while certainly getting many small details wrong and making mistakes and sometimes taking too long to come to the right conclusions, is still heading in a monotonically positive direction.
Parent
Re:first post (Score:5, Insightful)
But Science is about proving things, not suggesting every possible idea and disproving them one by one.
Where on Earth did you get that idea? One of the first things you learn about science is that it doesn't prove anything, only disprove. The scientific method is a three step process:
You observe phenomenon, create a theory that explains it and makes some predictions and then test these predictions. If the observations don't match the predictions you either discard or refine the theory. If they do, then you keep it around until you find some new observations that don't match up with the predictions.
The reason creationism is not science is that it makes no testable predictions. Whether it is true or not can not be tested and so is an irrelevant question to science.
Parent
Re:first post (Score:5, Insightful)
You and colmore are both right. Colmore beautifuly summarized how science actually operates. Your observations reflect understandings gleaned from the philosophy of science, in particular Karl Popper's falsifiability criteria. Popper developed this idea to show how one can delineate science from pseudo-science. It is a valuable philosophical insight and is useful as a criteria of demarcation between science and unscientific ideas. But, it is not a good foundation for understanding the actual methodologies used by science. Actual science proceeds based on some assumptions such as the uniformity of natural causes that cannot be proven, but which underlay belief in the validity of probabilistic induction and the idea that science illuminates "truth" in some sense and gives us greater knowledge of reality.
Parent
Re:first post (Score:5, Insightful)
As a working scientist: no he (colmore) didn't. Although his intentions were good.
In science you make some assumptions when creating your theory, but if you find evidence that indicates those assumptions are likely false then it's time to make a new theory. That INCLUDES such assumptions as the universe being consistent.
An excellent example of just that idea is quantum mechanics. The universe, it seems, isn't consistent in quite the way that classical physics thought it was: a cause doesn't always produce the same effect. When we discovered this, we designed quantum mechanics to take this aspect into account.
Both you and colmore use the word "prove." Science is not about proving things, and of course you cannot prove assumptions, or anything else, for that matter. In science there is no proof, because there is always the possibility that you will find a counterexample.
Parent
Re:first post (Score:5, Informative)
The most important thing that you need to understand is that the large number of "hot jupiters" that have been found have essentially disproven existing theories of solar system formation. This is not a case where a new theory is proposed to replace an existing theory that already explains most of the evidence ala Einsteinian physics replacing Newtonian physics. This is a case where we have essentially no theory at all that explains the observed evidence.
Parent
Re: (Score:3, Interesting)
From Douglas Adams [biota.org]:
I mean this is a great world, it's fantastic. But our early man has a moment to reflect and he thinks to himself, 'well, this is an interesting world that I find myself in' and then he asks himself a very treacherous question, a question which is totally meaningless and fallacious, but only comes about because of the nature of the sort of person he is, the sort of person he has evolved into and the sort of person who has thrived because he thinks this particular way. Man the maker looks at his world and says 'So who made this then?' Who made this? - you can see why it's a treacherous question. Early man thinks, 'Well, because there's only one sort of being I know about who makes things, whoever made all this must therefore be a much bigger, much more powerful and necessarily invisible, one of me and because I tend to be the strong one who does all the stuff, he's probably male'. And so we have the idea of a god. Then, because when we make things we do it with the intention of doing something with them, early man asks himself , 'If he made it, what did he make it for?' Now the real trap springs, because early man is thinking, 'This world fits me very well. Here are all these things that support me and feed me and look after me; yes, this world fits me nicely' and he reaches the inescapable conclusion that whoever made it, made it for him.
This is rather as if you imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in - an interesting hole I find myself in - fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for.