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How special is the Solar System? (Forwarded)
The next nearest star 4.3 light years away, Alpha Centuri A is a million
miles across or 1,227 times the size of our sun. It could have a very large solar system. Assuming the galaxy is 100,000 light years across go in to it from here about 25,000 light years (halfway to the center) and the stars are much closer together making solar system planets also close together.There must be billions of planets in this galaxy alone. No matter how they are formed there has to be millions of similar types and many binary star systems and mulit-star systems. I think the count is roughly 100 billion stars in this galaxy. Now think of 125 billion galaxies estimated by Hubble and you see very many stars and planets. "Andrew Yee" wrote in message ... Royal Astronomical Society Press Notice Issued by Dr Jacqueline Mitton, RAS Press Officer jmitton -at- dial.pipex.com tel: +44 (0)1223-564914 CONTACTS Dr Martin Beer University of Leicester, UK Tel: +44 (0)116 2231802 Email: Prof. Andrew King University of Leicester, UK Tel: +44 (0)116 2522072 Email: Dr. Mario Livio Space Telescope Science Institute, USA Tel: +1 410 338 4439 Email: Dr. Jim Pringle University of Cambridge, UK Tel: +44 (0)1223 337513 Email: ************************************************** ************ Date: 3rd August 2004 PN04-30 HOW SPECIAL IS THE SOLAR SYSTEM? On the evidence to date, our solar system could be fundamentally different from the majority of planetary systems around stars because it formed in a different way. If that is the case, Earth-like planets will be very rare. After examining the properties of the 100 or so known extrasolar planetary systems and assessing two ways in which planets could form, Dr Martin Beer and Professor Andrew King of the University of Leicester, Dr Mario Livio of the Space Telescope Science Institute and Dr Jim Pringle of the University of Cambridge flag up the distinct possibility that our solar system is special in a paper to be published in the Monthly Notices of the Royal Astronomical Society. In our solar system, the orbits of all the major planets are quite close to being circular (apart from Pluto's, which is a special case), and the four giant planets are a considerable distance from the Sun. The extrasolar planets detected so far -- all giants similar in nature to Jupiter are by comparison much closer to their parent stars, and their orbits are almost all highly elliptical and so very elongated. "There are two main explanations for these observations," says Martin Beer. "The most intriguing is that planets can be formed by more than one mechanism and the assumption astronomers have made until now -- that all planets formed in basically the same way -- is a mistake." In the picture of planet formation developed to explain the solar system, giant planets like Jupiter form around rocky cores (like the Earth), which use their gravity to pull in large quantities of gas from their surroundings in the cool outer reaches of a vast disc of material. The rocky cores closer to the parent star cannot acquire gas because it is too hot there and so remain Earth-like. The most popular alternative theory is that giant planets can form directly through gravitational collapse. In this scenario, rocky cores -- potential Earth-like planets -- do not form at all. If this theory applies to all the extrasolar planet systems detected so far, then none of them can be expected to contain an Earth-like planet that is habitable by life of the kind we are familiar with. However, the team are cautious about jumping to a definite conclusion too soon and warn about the second possible explanation for the apparent disparity between the solar system and the known extrasolar systems. Techniques currently in use are not yet capable of detecting a solar-system look-alike around a distant star, so a selection effect might be distorting the statistics -- like a fisherman deciding that all fish are larger than 5 inches because that is the size of the holes in his net. It will be another 5 years or so before astronomers have the observing power to resolve the question of which explanation is correct. Meanwhile, the current data leave open the possibility that the solar system is indeed different from other planetary systems. NOTES 1. Currently around 100 extrasolar planets are known which have been detected through the wobble of their host stars caused by the motion of the planets themselves. 2. The paper has recently been accepted by the Monthly Notices of the Royal Astronomical Society but no publication date has yet been set. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.732 / Virus Database: 486 - Release Date: 7/29/2004 |
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How special is the Solar System? (Forwarded)
Rodney Kelp wrote: [Forwarded press release] HOW SPECIAL IS THE SOLAR SYSTEM? On the evidence to date, our solar system could be fundamentally different from the majority of planetary systems around stars because it formed in a different way. If that is the case, Earth-like planets will be very rare. If I was an astronomer, I'd be very wary of making this kind of statement. They've almost always proved wrong in past. Given that we can't detect Earth size planets yet, nor are very good at finding multi-year orbit big planets, this is just pure speculation. And this type of speculation, that the Earth, Sun, or solar system is in some way special, has a very bad track record. The principle of mediocrity applies here (assume we are average unless there is some strong evidence against it), and there is no evidence against it yet. Lou Scheffer |
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How special is the Solar System? (Forwarded)
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How special is the Solar System? (Forwarded)
"Alain Fournier" wrote in message ... wrote: Rodney Kelp wrote: Yes there is evidence against it. The evidence isn't very strong but we are now getting some serious data on the matter. Well the evidence is somewhat strong that our solar system is fundamentally different from the majority of planetary systems around stars. It is much weaker about Earth-like planets being very rare. Most planets found to date are Jupiter sized or bigger in an elliptical orbit with periapsis less than 1 AU. If Jupiter had an elliptical orbit with periapsis less than 1 AU, then Earths orbit wouldn't be stable and Earth wouldn't be. I suspect we've too few samples to draw any real conclusions. I remember talking to an astronomer about extra-solar planets in the early 90's and he was not then prepared to say they existed at all because the data was too flimsy. Given the size and scope, Earths might be rare but I do find it hard to believe they are unique. Dave |
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How special is the Solar System? (Forwarded)
Dave O'Neill dave @ nospam atomicrazor . com wrote:
"Alain Fournier" wrote in message ... wrote: Rodney Kelp wrote: Yes there is evidence against it. The evidence isn't very strong but we are now getting some serious data on the matter. Well the evidence is somewhat strong that our solar system is fundamentally different from the majority of planetary systems around stars. It is much weaker about Earth-like planets being very rare. Most planets found to date are Jupiter sized or bigger in an elliptical orbit with periapsis less than 1 AU. If Jupiter had an elliptical orbit with periapsis less than 1 AU, then Earths orbit wouldn't be stable and Earth wouldn't be. I suspect we've too few samples to draw any real conclusions. I remember talking to an astronomer about extra-solar planets in the early 90's and he was not then prepared to say they existed at all because the data was too flimsy. Umm... Earth style planets are coupe of orders o magnitude what we can detect. Presently it would probably have to massively collide with something for us to detect. This is about to change in not too distant fture so peple saying such things now is particularily odd. Given the size and scope, Earths might be rare but I do find it hard to believe they are unique. It depdends on what you mean by "Earths" - given that this system has 2 2/3-s, I don't really see why they should be rare. Dave -- Sander +++ Out of cheese error +++ |
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How special is the Solar System? (Forwarded)
"Alain Fournier" wrote in message ... Yes there is evidence against it. The evidence isn't very strong but we are now getting some serious data on the matter. Well the evidence is somewhat strong that our solar system is fundamentally different from the majority of planetary systems around stars. It is much weaker about Earth-like planets being very rare. Most planets found to date are Jupiter sized or bigger in an elliptical orbit with periapsis less than 1 AU. If Jupiter had an elliptical orbit with periapsis less than 1 AU, then Earths orbit wouldn't be stable and Earth wouldn't be. Keep in mind that most of the techniques used are more LIKELY to find that sort of system than ours. Mostly they focus on the wobble of a star, a star with a Jupiter class planet close in will have a more easily detectable wobble than one further out, for two reasons: 1) Mass closer causes a larger effect. 2) Shorter orbit causes wobbles more often. Alain Fournier |
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How special is the Solar System? (Forwarded)
Greg D. Moore \(Strider\) ) wrote:
: "Alain Fournier" wrote in message : ... : : Yes there is evidence against it. The evidence isn't very strong : but we are now getting some serious data on the matter. Well : the evidence is somewhat strong that our solar system is : fundamentally different from the majority of planetary systems : around stars. It is much weaker about Earth-like planets being : very rare. Most planets found to date are Jupiter sized or bigger : in an elliptical orbit with periapsis less than 1 AU. If Jupiter : had an elliptical orbit with periapsis less than 1 AU, then : Earths orbit wouldn't be stable and Earth wouldn't be. : : Keep in mind that most of the techniques used are more LIKELY to find that : sort of system than ours. : Mostly they focus on the wobble of a star, a star with a Jupiter class : planet close in will have a more easily detectable wobble than one further : out, for two reasons: : 1) Mass closer causes a larger effect. : 2) Shorter orbit causes wobbles more often. Synodic periods of large planets (i.e. Jupiter ans Saturn)? That period is 20 years even though Jupiter's period is 12 years and Saturn's is 29. Who is to say that these extrasolar planets don't have a similar makeup like Jupiter and Saturn? Eric : Alain Fournier : |
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How special is the Solar System? (Forwarded)
Alain Fournier wrote:
Yes there is evidence against it. The evidence isn't very strong but we are now getting some serious data on the matter. Well the evidence is somewhat strong that our solar system is fundamentally different from the majority of planetary systems around stars. It is much weaker about Earth-like planets being very rare. Most planets found to date are Jupiter sized or bigger in an elliptical orbit with periapsis less than 1 AU. If Jupiter had an elliptical orbit with periapsis less than 1 AU, then Earths orbit wouldn't be stable and Earth wouldn't be. No - its just that that type of objects and star systems are what we can detect best so of course they are most numerous. Oh, and even with a hot super-Jupiter you could get terrestrial planets in habitable zone given favourable presence of smaller gas giants. Alain Fournier -- Sander +++ Out of cheese error +++ |
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How special is the Solar System? (Forwarded)
Sander Vesik wrote: Alain Fournier wrote: Yes there is evidence against it. The evidence isn't very strong but we are now getting some serious data on the matter. Well the evidence is somewhat strong that our solar system is fundamentally different from the majority of planetary systems around stars. It is much weaker about Earth-like planets being very rare. Most planets found to date are Jupiter sized or bigger in an elliptical orbit with periapsis less than 1 AU. If Jupiter had an elliptical orbit with periapsis less than 1 AU, then Earths orbit wouldn't be stable and Earth wouldn't be. No - its just that that type of objects and star systems are what we can detect best so of course they are most numerous. Oh, and even with a hot super-Jupiter you could get terrestrial planets in habitable zone given favourable presence of smaller gas giants. We can detect large planets close to the star. But why are they in elliptical orbits. We can detect circular orbits as well as elliptical orbits. I agree that there could still be lots of Earth like planets. But it does seem likely that our solar system is atypical, if only because our planets close to the sun are in circular orbits. It still is early to declare what is a typical solar system but we are now getting some data. And that data is not pointing towards our solar system being typical. Alain Fournier |
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How special is the Solar System? (Forwarded)
Alain Fournier wrote:
Sander Vesik wrote: Alain Fournier wrote: Yes there is evidence against it. The evidence isn't very strong but we are now getting some serious data on the matter. Well the evidence is somewhat strong that our solar system is fundamentally different from the majority of planetary systems around stars. It is much weaker about Earth-like planets being very rare. Most planets found to date are Jupiter sized or bigger in an elliptical orbit with periapsis less than 1 AU. If Jupiter had an elliptical orbit with periapsis less than 1 AU, then Earths orbit wouldn't be stable and Earth wouldn't be. No - its just that that type of objects and star systems are what we can detect best so of course they are most numerous. Oh, and even with a hot super-Jupiter you could get terrestrial planets in habitable zone given favourable presence of smaller gas giants. We can detect large planets close to the star. But why are they in elliptical orbits. We can detect circular orbits as well as elliptical orbits. I agree that there could still be lots of Earth like planets. But it does seem likely that our solar system is atypical, if only because our planets close to the sun are in circular orbits. It still is early to declare what is a typical solar system but we are now getting some data. And that data is not pointing towards our solar system being typical. A lot of these would have been migrations and not as they formed. Alain Fournier -- Sander +++ Out of cheese error +++ |
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