How special is the solar system?

[admiral_ju00]

That is the title of this paper.

 

What do you guys in particular Martin and Jana think about this?

 

http://xxx.arxiv.org/PS_cache/astro-ph/pdf/0407/0407476.pdf

[Martin]

That is the title of this paper.

 

What do you guys in particular Martin and Jana think about this?

 

http://xxx.arxiv.org/PS_cache/astro-ph/pdf/0407/0407476.pdf

 

I like it a lot when people find recent arxiv.org papers to discuss and this one is recent----July 2004----and this is a really really interesting question

 

 

and there is a bunch of data always coming in on this all the time (the extrasolar planet search) that is relevant to answering, obviously because the more planet-systems we know the better we can say how special sol-systme is

 

and there is also relevent theory----if we have good models of how stars and their planet systems form we can run simulations from the model and see how often systems like ours come up

 

so all that is good

 

but that said, I dont happen to have any expertise about it!!!!

hopefully someone else can comment on this paper who has more

background-----if there is totally lacking anybody I will eventually take a stab

 

 

http://arxiv.org/astro-ph/0407476

 

"How special is the Solar System?"

Authors: M.E. Beer (1), A.R. King (1), M. Livio (2), J.E. Pringle (3) ((1) Leicester, (2) STScI, (3) Cambridge)

Comments: 6 pages, 3 figures

 

"Most mechanisms proposed for the formation of planets are modified versions of the mechanism proposed for the solar system. Here we argue that, in terms of those planetary systems which have been observed, the case for the solar system being a typical planetary system has yet to be established. We consider the possibility that most observed planetary systems have been formed in some quite different way. If so, it may be that none of the observed planetary systems is likely to harbour an earth-like planet."

[Martin]

sorry to be stuffy about this but i always give the authors a once-over to see the credentials

Pringle at Cambridge has published 40 papers

Martin Beer at Leicester is the young one of the bunch with only half a dozen.

The other two. Andrew King and M.Livio have each published over 70

and they are at Univ. Leicester and at SpaceTelescopeScience Inst.--Maryland and have collaborated before on earlier papers about planet-formation

 

so these people seem like mainstream upper-middle-level experts on extrasolar planet formation---this is cool, cant ask for better as far as authorship.

[Martin]

OK, not every paper you come across in arxiv that has a nice title is revolutionary or even interesting!

 

But by good fortune this paper has a revolutionary idea and is actually interesting----but it will take 5 or 10 years to confirm and sort it out.

 

the idea is that the sol system may have formed in a comparatively metal-poor region and be unusual in having its gas giants 5-10 AU out

 

for these people "metal" means element heavier than carbon, like.

 

other planet systems formed in a comparatively rich region and

if you have a lot of metal then you quickly condense a lot of rock

(silicon, oxygen, calcium, aluminum, iron are metals and make rocks)

 

then the rocky bits form nucleus and you quickly condense your gas giants while there is still a lot of gas in the system and this slows the planets down and they spiral in close

 

so all those other system have Jupiters like around 1 AU (damn close)

 

but if you are initially metal POOR then rocks form slowly and they nucleate slowly and the gas giants like Jup and Sat form in a cleaner envirnonment where the gas that could slow them down has already mostly been expelled.

 

so the gas giants DONT spiral in and you have a nice system like ours with the giants out at 5 and 10 AU

 

so far very few of those have been found so Sol system is an "outlier"

it is a statistical exception in the tail of some distribution---it lies outside

the main bunch.

 

Now the caveat. It takes more years of watching to observe a gas giant at 10 AU because you have to watch the wobble for a long time because it takes a long time to go round the star.

 

Well, this is a very interesting question. There may be several different scenarios for forming a planetary system, depending on things like metal rich metal poor and maybe other things we didnt think of yet. andthat could affect the statistics of what kinds of planets there are in the world.

 

Admiral asked for comment on this paper. this is my comment (based on

no expertise in the subject matter)

[admiral_ju00]

Interesting. Thanks Martin.