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."
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)
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?
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.
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.
Re:is Jupiter's orbit stable... (Score:2, Interesting)
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
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.
Re:Why focus on just this one factor? (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.
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
_Implications_ of Hot Jupiter means Earth is rare (Score:3, Interesting)
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...
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.
Re:Well, that does it... (Score:3, Interesting)
Further, its not like Intelligent Design, because planetary formation models are a testable and falsifiable hypothesis.
Re:Rare? (Score:2, Interesting)
Re:is Jupiter's orbit stable... (Score:3, Interesting)
Jupiter is also on the small side for the biggest planet in a system, so it would seem.
There's also been speculation that Jupiter's stable orbit has helped out life by clearing out a lot of rocky debris from the inner solar system.
If we had major impacts once every million years or so, complicated life would have a much tougher time developing.
Re:gas giants? (Score:2, Interesting)
If gas and dust get blown away, what's to say that rocky planets weren't originally gas giants?
That would be the Nebular Hypothesis [wikipedia.org] model of solar system formation. It's more the case that the gas giants were originally rocky/icy planets. A planet has to grow out of rock/metal/ice to about 10-20 Earth masses before it can even hold on to appreciable amounts of gas. Temperatures in the inner solar system are too high for ice to condense, so there's less material available to build planets, and the inner planets can't get that big.
The "Hot Jupiters" (which would be a good name for a rock band) probably formed further out and migrated inward in a swath of destruction that ejected any inner planets from the system. The question is why didn't our own Jupiter Classic(TM) do this to us?
Mod Parent Insightful! (Score:3, Interesting)
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 towards the sun. If any of them wandered closer to the sun, I'll bet some of those moons will have a high probability of life.
Furthermore, the smaller rocky planets in the center certainly have a chance of becoming the moon of a gas giant as it passes by. Granted, any existing complex life on those planets might be wiped out by the change, but that doesn't mean new complex life wouldn't arise afterwards once the gas giant settles into a stable orbit.
The conclusion that our type of system is rare is probably valid based on the new models. But the conclusion that intelligent life is equally as rare is probably invalid.
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.
Re:Mod Parent Insightful! (Score:3, Interesting)
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?
I call bullshit (Score:2, Interesting)
Re:wake me up (Score:2, Interesting)
What nobody mentions is that G. 581 is a FLARE STAR, prone to blowing up regularly, thus laying waste to whatever bugs or Linux hackers may be on said close-revolving planet.
People should read Ward & Brownlee's "Rare Earth" [amazon.com]. And don't launch into spittle-flecked diatribes on intelligent design, because Ward & Brownlee don't believe in it, and STILL think Earth is extremely rare, if not unique in the universe.
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:Calculating a planetary system. (Score:2, Interesting)
Rather pessimistic of you, considering how little we know, and how much is just speculation... A lot of what you write doesn't make sense considered what we know.
We don't know if life could develop around other elements than carbon chains, but there certainly are several possibilities, they just require unlikely environments. But we don't know that such environments don't exist. As an example, we don't really know much about high-pressure chemistry that might be going on at the solid surface or in the oceans of different gas giants, so it's kind of arrogant to rule out any life developing there.
And details like rotation... At the bottom of an ocean, the wind doesn't matter much. With active enough geology, there could easily be enough surface features to create a lot of protective places on land, too. Or "plants" could just grow strong enough to stand the winds, and then provide shelter for less robust life forms. The possible possibilities are endless, so ruling stuff out based on detail like doesn't make sense to me.
About color of parent star, certainly photosynthesis on Earth developed to match the colour of our sun. In another planet, the chemical process, the molecules and the structures involved, would of course be optimized for it's parent star. I mean, that's what life does for living, optimization, and you'll have hard time proving non-existence of any plausible photosynthesis mechanism for pretty much any star.
Now it may turn out that any other kind of life, except our carbon-DNA-kind just isn't practical in our Universe, either there just aren't suitable environments, or the chemistry just doesn't work. But based on what possibilities on exotic life we have imagined, and adding the unknown possibilities we haven't imagined, some of them probably work.