

Our Solar System Isn't Normal - sajid
http://www.npr.org/blogs/krulwich/2013/05/06/181613582/our-very-normal-solar-system-isn-t-normal-anymore

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tocomment
I would argue the exo-planets we have found so far are a very biased sample.
We don't have great technologies for detecting solar systems like ours. And at
least the first few years of planet hunting we'll tend to find a lot of large
giants orbiting close to their stars since they're the easiest to find.

~~~
3JPLW
I was very surprised that the article made no mention of such a bias. It was
my first thought, too. I'm not terribly up-to-date on how Kepler has been
detecting planets, but isn't it due to the 'wobble' of the stars? Surely
they'll find planets that orbit faster (and wobble their stars faster) first.
It'll take many many years of very consistent observations (or one very lucky
day) to see a wobble (or occlusion) from a planet like our Jupiter.

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schiffern
Kepler uses occlusion, not wobbling.

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teamonkey
Yes, and it's designed to detect Earth-sized planets as well as larger gas
giants.

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Tuna-Fish
But detection probability is directly correlated to planet size and shortness
of the local year.

Eventually, Kepler and Kepler-like probes will be able to locate all earth-
like planets with orbits that cross the path between the star and us. However,
this technique will find the larger planets with shorter orbits first.

~~~
teamonkey
Yes indeed, but the point is that according to current theories Kepler should
already be finding more Earth-sized planets than it has and few inner gas
giants. The observable evidence does not match the predicted model.

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qdog
I think everyone here concentrating on sampling bias is missing the point.

The evidence in solar systems so far does NOT fit the theory involving a frost
line, and giants like Jupiter are unexpectedly observed tightly orbiting suns.
Whether our solar system is normal is conjecture, but our model for how solar
systems are(were?) formed is obviously flawed. Pretty interesting find, imho.

~~~
chc
I don't see how the fact that gas planets are capable of migrating inward
shows that our model for planetary formation is deeply flawed. I didn't think
the current model said that it was impossible for planets to migrate inward.

The point about sampling bias is that our current techniques are bad at
spotting systems like ours. If this is true (I think it is, but I'm not
qualified to say), we wouldn't expect the evidence to fit our theory even if
our theory were true because we are nearly incapable of finding evidence that
does fit our theory no matter how much of it there is out there.

~~~
qdog
Perhaps I mangled that a bit, instead of frost line I should have just said
the seemingly most popular theory of how the solar system formed. From the
article the bit that caught my eye:

Mike Brown, an astronomer at Caltech, wrote me that while everybody is busy
hunting for an Earth-like planet, they missed this story. "Before we ever
discovered any [planets outside the solar system] we thought we understood the
formation of planetary systems pretty deeply." We had our frost line. We knew
how solar systems formed. "It was a really beautiful theory," he says. "And,
clearly, thoroughly wrong."

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Filligree
It's true that this could still turn out to be mostly observational bias, but
I feel like everyone is missing the monkey wandering across the corridor.

The anthropic principle, that is. Isn't it possible that, while gas planets
clustered closely around the star is the normal shape of solar systems, such a
configuration is not amenable to complex life?

~~~
IsaacL
It would also be a good candidate for the Great Filter - the hidden factor
that has stopped the development of all the other intelligent civilisations
that would otherwise be out there. That would mean this is good news - we'd
rather the Great Filter lies in our past (because that means we've already
survived it) than in our future.

~~~
gwern
I don't think it's a good candidate; certainly it pushes some amount of the
Filter into our past, but even if only 1 in 700 solar systems is Sol-like,
there are so many we'd still expect to see tons of aliens. For a single-step
Filter or for solar systems to even be a majority of the filter, you need a
step so unlikely that it can push the presence of interstellar life down from,
like, trillions of star systems to ~1.

~~~
IsaacL
Thanks for the reply, and yes, that makes sense. What would you predict as the
most likely other steps in the filter?

Looking at our own planet, I would guess that it's a combination of a) it
being simply infeasible to send large animals to distant stars (we haven't yet
colonised the moon or even made a serious attempt to colonise low earth orbit,
and we might not do so before we run out of cheap energy) and b) technological
singularities.

~~~
gwern
> What would you predict as the most likely other steps in the filter?

I don't know. Robin Hanson blogs a lot about it, but none of the steps seem
terribly plausible although my favorite currently is big brains being feasible
- in a number of ways, heads seem to be rare, big brains even rarer, and the
costs of big brain _almost_ too expensive to bear because neurons seem to be
unable to get more efficient; one paper I liked on the topic was
[http://www.pnas.org/content/early/2012/06/19/1201895109.full...](http://www.pnas.org/content/early/2012/06/19/1201895109.full.pdf)
but you can find a lot of relevant material in
<http://www.gwern.net/Drug%20heuristics>

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ra
Kepler has been revolutionary in discovering these 700 odd planetary systems,
but we can't even begin to imagine what surprises await for when we point the
James Webb Space Telescope at them.

One of JWSTs mission objectives is to study the planetary systems discovered
by Kepler, and the origins of life.

[http://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Miss...](http://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Mission)

~~~
tocomment
What specifically will the telescope tell us about this exo-planets? It surely
can't image them directly, right?

~~~
ra
Not quite, but JWST will be out at the L2 point, beyond the moon in
essentially what amounts to an earth-matching solar orbit.

It's large aperture infrared sensors will have an unobstructed view of the
universe (unlike Hubble which is in low earth orbit, and so only gets 90
minute windows of observation).

Basically, using IR spectroscopy we will be able to analyse the atmospheric
composition as well as the thermal emissions of exoplanets.

Finally, JWST won't be limited to a small, fixed field of view like Kepler.

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unreal37
I had no idea that:

"Or maybe it got ejected — astronomers are finding emigrant planets, lonely
orbs that wander the universe with no star, just drifting. Maybe one of those
used to live here."

There are planets not orbiting stars? I searched Google for "emigrant planets"
and the npr article is the number 1 result for that. I think he invented the
term. What are these called if I wanted to find more information about them?

~~~
johngalt
They are more commonly called rouge planets.

<http://en.wikipedia.org/wiki/Rogue_planet>

~~~
MartinCron
I always thought Mars was the rouge planet.

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Shivetya
Being a long time fan of 4x games, well of space games in general, this
article makes me smile. I remember reading game forums where one subject that
always arose was galaxy and system formations. So many of our concepts are
strictly based on the very little observable data we have. Its great to live
in a time when many assumptions are proven to be just that.

Now the question that remains is, which configurations are more favorable to
life, not just as we know it.

~~~
yolesaber
A bit off-topic, but can you recommend any recent space 4x games to check out?
The last one I played was Galactic Civilizations II and I enjoyed it
immensely.

~~~
ekimekim
There's a new-ish one called Endless Space, which I would describe as Gal Civ
inspired.

It's a little weird in that all players take turns simultaneously (you still
have movement restrictions, etc, but it adds a real-time component because you
want to wait to react to your opponent's movements, but also there's a time
limit). The impression I got was that it was a way to speed up gameplay (less
sitting around while others make their moves).

But it's a cool little game, _lots_ of race customisation (with a few truly
unique race benefits), interesting four-category tech tree (and equivalently,
four ways to win), custom ship classes built out of components (like Gal Civ).

The combat is a little weird, they have some card-game-like thingy that can
significantly influence battle outcomes.

EDIT: Not a turn-based game but there's also this:
<http://triton.ironhelmet.com/>

Neptune's Pride is an always-on real time game played over several weeks in
matches of up to 12 players. The mechanics are refreshingly simple, and
there's a focus on diplomacy and betrayal in order to come out top.

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gweinberg
I think the author has the "frost zone" theory backwards. It's not that it's
too cold for rocky planets to form outside the frost zone (after all, there
are some planet-sized moons out there) but rather that inside the frost zone
it is too hot for planets to hold on to hydrogen, so you don't get gas giants.

I would think that a gassy planet close to a star would have to have a really
big solid or liquid core of heavy elements.

~~~
teamonkey
The frost line is the point at which ice crystals can form of the major
planetary gasses. The theory was that outside the frost line these crystals
would add to the density of particulates in the region, therefore larger
planets would form outside the frost line and they would have a greater
proportion of gasses than the inner planets.

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namuol
Couldn't the techniques we are using be biasing the results? Maybe solar
systems like ours are simply harder to detect.

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NicolasBeuzeboc
I agree, I'm speculating that by looking at a star wobble or it's brightness
decrease that method of detection would bring up all these systems with close
orbiting planets that would be bigger than "normal".

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Gravityloss
And how many of those close-to-the-sun planets exclude the existence of earth-
like planets a bit further out?

Maybe if they're Jupiter-sized, then they would make some orbits further out
unstable, but if they're smaller...

The system can be different than ours but still just as habitable, or even
more so.

~~~
vec
Probably not, assuming our current theories about how these systems form are
correct. Our best guess is that hot jupiters form about where our jupiter or
saturn is and their initial orbit decays inward. If so, that would tend to
destroy the orbit of anything vaguely earth-sized on the way in.

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peter303
All the conventional planet hunting methods are biased towards fast, large,
close-in planets. If we could run Kepler for 20 years we might see systems
more like ours.

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bitwize
That is AWESOME. The fact that there is so much diversity of planets and solar
systems out there flabbergasts me. I don't even care about what kind or
whether there's life out there -- just thinking about how there are so many
different worlds with prevailing conditions that I never even dreamed of gives
me the chills.

Space... space... so much space... gotta see it all...

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jammi
Regarding no gassy planets near our sun: The rocky ones, including earth, [are
supposedly the cores of old gassy
ones]([http://www.astrobio.net/exclusive/4220/rocky-planets-
could-h...](http://www.astrobio.net/exclusive/4220/rocky-planets-could-have-
been-born-as-gas-giants)).

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pm
Does anyone know how far away we are from being able to confirm the presence
of planets as we might on a photograph? Or the obstacles we face getting to a
high enough resolution?

~~~
grkvlt
Minus five years? See this HST image from 2008:
[http://hubblesite.org/newscenter/archive/releases/2008/39/im...](http://hubblesite.org/newscenter/archive/releases/2008/39/image/e/format/xlarge_web/)

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Allower
When I read "nature prefers" and the author admits the data's sample size is
less than a drop in an ocean (we found < 1000 solar systems), I just have to
stop reading.

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jksmith
What is normal in the context of the universe? What is context in the context
of the universe?

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mrab
If space is infinite, it is entirely possible that we are ridiculously close
to the norm.

~~~
mrab
Or that there isn't a norm at all!

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tenpoundhammer
This is a grand example of our infinite hubris.

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calinet6
"We have to figure out why our solar system turned out different from all the
others."

Not entirely—we have to understand statistics and the anthropic principle,
which states "observations of the physical Universe must be compatible with
the conscious life that observes it." (Wikipedia:
<http://en.wikipedia.org/wiki/Anthropic_principle>). In other words, our
situation appears "perfect" because it was one of the many random combinations
available which produced _an observer_ able to look at it. In other words, the
fact that our solar system is so stable might just be a random anomaly, but
the fact that it was so stable resulted in our existence, and therefore our
contemplation of the fact.

As an analogy, winning the lottery is extremely rare—if you go and interview
the person who won the lottery, they must think themselves very lucky. But on
the grand scale, the probability of someone winning the lottery in the entire
pool is exactly one. We know that a winner necessarily exists—just as we know
that we, as winners of the cosmic lottery, necessarily exist. But that just
tells us that someone won the lottery—something we already knew.

It may be that the lottery is rigged, and that there are some characteristics
of our particular solar system which are amenable to life, and those things
are definitely valuable to study and find out, so that we might be able to
recognize other solar systems capable of supporting life in some way.

But by no means is our solar system special in any light: it's only special in
that its particular conditions produced lifeforms able to observe it.

"We are a way for the cosmos to understand itself." - Carl Sagan

Another random question: are the planetary systems we've discovered similar to
_each other?_ If ours is significantly deviant from a significant clustering
that would be pretty interesting. And of course, that's surely what the
original findings were probably about.

~~~
kpierre
> But by no means is our solar system special in any light: it's only special
> in that its particular conditions produced lifeforms able to observe it.

sorry, but i don't understand what's the logic here? it's not special, but
it's only very special in sustaining/producing life? isn't that more than
enough to call it special? :-)

~~~
pekk
Not in the requisite sense. Suppose that our existence depended on a purely
random roll of a six-sided die coming up as 1. If the roll had come up
anything else, we would not be here to reflect on it. But if it did come up as
1, that does not mean a mystical force guaranteed that it came up as 1.

Our existence (whether likely or not) does not constitute evidence that our
existence was guaranteed or predetermined. Low-probability events happen
sometimes, their actually having happened once does not make them high-
probability.

~~~
kpierre
it seems like you, and the top comment are interpreting this news story as
some attack on atheism? i don't see how that's even related. is that your
preemptive strike against non-atheistic interpretation?

~~~
calinet6
Absolutely not. My intention was to broaden the point by introducing the mind-
blowing anthropic principle and a new perspective on the conditions leading to
life, nothing more.

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CyberDroiD
Goof balls can't even see most of the solar systems, and they are saying what
is and what is not normal?

Hubris alert!

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transfire
Oh Heaven for Betsy. Every time some nitwit looks at new data with results
they did not expect, suddenly every thing we have ever known is wrong. Give me
a break.

Here's a "lightbulb" for you: A large gas giant near a star is created in the
same fashion as a binary star system (a formation that is quite common) with
the simple difference that the planet did not get enough material to actually
become a star.

