Is our solar system typical?

[Corsair 115]

... the Sun is bigger and brighter than at least 96% of the stars in the Galaxy; it is most certainly not a "typical star". (Typical star is an M-class dwarf.)

My understanding it's also unusual in that it contains a higher proportion of 'metals' (elements heavier than helium) than comparable stars found in our local neighbourhood.

 

[Senex]

We are all remnants of a supernova.

Typical or not -- it doesn't suck to be alive.

It's amazing and statistically improbable.

 

[MG1962]

My understanding it's also unusual in that it contains a higher proportion of 'metals' (elements heavier than helium) than comparable stars found in our local neighbourhood.

The thing to remember, the stars we are currently traveling with are not the stars the sun started life with back in the day. In terms of the metal our star contains, it is not that unusual for the time frame the Sun formed, stars with a lot of metal are known as population I stars.

 

[MG1962]

Let me phrase it a bit more strongly: The whole notion of Copernican Principle -- we live on a typical planet of a typical star in a typical galaxy, and the way things are here is the way things are (mostly) out there, -- is completely unsubstatiated wishful thinking. In fact, the middle part of the above statement is blatantly untrue despite having been repeated in countless textbooks -- the Sun is bigger and brighter than at least 96% of the stars in the Galaxy; it is most certainly not a "typical star". (Typical star is an M-class dwarf.)

But you leave out the bit about formation rates. The galaxy is populated with smaller dwarf class stars simply because of their longevity.

 

[Mark6]

So what?

 

[Puppycow]

Let me phrase it a bit more strongly: The whole notion of Copernican Principle -- we live on a typical planet of a typical star in a typical galaxy, and the way things are here is the way things are (mostly) out there, -- is completely unsubstatiated wishful thinking. In fact, the middle part of the above statement is blatantly untrue despite having been repeated in countless textbooks -- the Sun is bigger and brighter than at least 96% of the stars in the Galaxy; it is most certainly not a "typical star". (Typical star is an M-class dwarf.)

Either life/multicellular life/intelligence require highly unusual conditions, or they do not. If the latter is the case, we will see many solar systems similar to ours, and Copernican Principle will be vindicated. If the former is the case, we will not see many systems similar to ours -- the fact that we are here only proves life-bearing conditions are possible, not that they are common.

In the Middle East occures a bizarre terrain called sabka. It is essentially a tar pit, covered by compressed sand. The sand crust is strong enough for people and camels to walk on, but collapses under trucks or tanks, miring them in tar like sabertooth tigers in La Brea tar pit. Sabka occures nowhere else on Earth. Some insect living on/in sabka could apply Copernican Principle to say "We are not special. Everywhere should be like it is here". And would be utterly wrong.

Does it mean laws of physics -- or even laws of geology, -- are different in Middle East than elsewhere on Earth? Of course not -- it just means that for sabka to exist, a set of rather unlikely conditions (each of them individually entirely within the realm of these laws) must come together. OTOH, sand in various forms exists just about everywhere. Wether our planetary system is akin to sand or akin to sabka is yet to be determined. And so far (weak) evidence points to sabka.

Interesting post. Thanks.

 

[Craig B]

That means that there are at least two possible evolutions of solar systems. I wonder if there are any differences in the stars themselves between the two systems?

It has been argued that while a gas giant in the outer part of a solar system protects the inner planets from colliding comets - we have seen Jupiter performing this service - a star-hugging "hot Jupiter" would be useless, or worse. So perhaps life, or at any rate complex life, appears only in one of these kinds of systems.

 

[Craig B]

Let me phrase it a bit more strongly: The whole notion of Copernican Principle -- we live on a typical planet of a typical star in a typical galaxy, and the way things are here is the way things are (mostly) out there, -- is completely unsubstatiated wishful thinking. In fact, the middle part of the above statement is blatantly untrue despite having been repeated in countless textbooks -- the Sun is bigger and brighter than at least 96% of the stars in the Galaxy; it is most certainly not a "typical star". (Typical star is an M-class dwarf.)

The school of thought in opposition to which the Copernican Principle was formulated asserted not merely that the earth was not an average place, but that it was a singular and transcendentally special place, with a divinely-ordained central position in space and time. In relation to that the CP is powerfully substantiated. The sun is not an average star in mass, but it belongs to a reasonably normal category of stars.

This is not to say that there are lots of things like us out there - nobody has the slightest idea if there are or not - merely that there may be other things comparable with us somewhere else, and that we are not central, or favoured, however rare we may be.

 

[Corsair 115]

It has been argued that while a gas giant in the outer part of a solar system protects the inner planets from colliding comets - we have seen Jupiter performing this service - a star-hugging "hot Jupiter" would be useless, or worse..

There is also the problem that, under the current understanding of planetary formation, a Jupiter-like gas giant can't form close to its star. So the theory is that such gas giants formed further out and then gravitation interactions with other planets, especially other gas giants, eventually resulted in the planet ending up close to the star.

 

[Craig B]

There is also the problem that, under the current understanding of planetary formation, a Jupiter-like gas giant can't form close to its star. So the theory is that such gas giants formed further out and then gravitation interactions with other planets, especially other gas giants, eventually resulted in the planet ending up close to the star.

Which would presumably destroy any rocky inner planets, or eject them from that stellar system!

 

[Mark6]

The school of thought in opposition to which the Copernican Principle was formulated asserted not merely that the earth was not an average place, but that it was a singular and transcendentally special place, with a divinely-ordained central position in space and time. In relation to that the CP is powerfully substantiated. The sun is not an average star in mass, but it belongs to a reasonably normal category of stars.

True, and in a way Copernican Principle was a natural reaction -- especially back when there was no way to tell if it went overboard. However nowadays a) there is evidence it went overboard, and b) there is an example of very similar thinking which turned out to be quite wrong. I am talking about theory of "gradualism" in paleontology. Gradualism was a reaction to/denial of Cuvier's "catastrophism": Cuvier did not know about evolution, thought all species existed unchanged since Creation, and that every extinct species died out when some catastrophe (volcano, flood, whatever) encompassed that species' entire range.

When paleontogists realized that species do change with time, they rejected Cuvier completely. Through first half of 20th century it was a matter of faith that ALL extinctions occur gradually, over geological time. And when Alvarez realized that asteroid impact did in the dinosaurs, paleontologists resisted the idea very strongly. You could say he went against their religion -- the anti-Cuvier religion. Guess what -- Cuvier was not 100% wrong. Catastrophes can cause extinctions. Assumption of gradualism went overboard.

 

[Mark6]

Which would presumably destroy any rocky inner planets, or eject them from that stellar system!

Unless they formed after the gas giants migrated.

 

[Craig B]

True, and in a way Copernican Principle was a natural reaction -- especially back when there was no way to tell if it went overboard. However nowadays a) there is evidence it went overboard, and b) there is an example of very similar thinking which turned out to be quite wrong. I am talking about theory of "gradualism" in paleontology. Gradualism was a reaction to/denial of Cuvier's "catastrophism": Cuvier did not know about evolution, thought all species existed unchanged since Creation, and that every extinct species died out when some catastrophe (volcano, flood, whatever) encompassed that species' entire range.

When paleontogists realized that species do change with time, they rejected Cuvier completely. Through first half of 20th century it was a matter of faith that ALL extinctions occur gradually, over geological time. And when Alvarez realized that asteroid impact did in the dinosaurs, paleontologists resisted the idea very strongly. You could say he went against their religion -- the anti-Cuvier religion. Guess what -- Cuvier was not 100% wrong. Catastrophes can cause extinctions. Assumption of gradualism went overboard.

I was thinking of exactly that as an analogy of your CP example! Gradualists did overdo their opposition to the idea of catastrophes as the cause of extinctions or other significant events. And they did so, not because such individual catastrophes contradict gradualist evolution - for most certainly they don't - but because they were over sensitive to any idea that savoured of the "catastrophic principle" to which they rightly counterposed evolution. But essentially the gradualists were right and the catastrophists wrong.

Example. Traditional Christianity holds that languages were created all at once at the Tower of Babel, catastrophically. Modern scholars believe that languages evolve over time. But of course a language can disappear very quickly indeed if its speakers are annihilated by war or epidemic, or overwhelmed by bearers of another culture. This catastrophic possibility is in no way to be taken as evidence for the truth of the Babel story, or other similar myths.

 

[Trakar]

Unless they formed after the gas giants migrated.

The only problem with this is that it really alters the dynamics of planetary formation; I'm not sure you could get (structurally or compositionally) a Solar type inner planetary system if you have an early formed gas giant that migrates through the inner system.