
Our Solar System Is Even Stranger Than We Thought - extraterra
https://blogs.scientificamerican.com/observations/our-solar-system-is-even-stranger-than-we-thought/
======
vanderZwan
> _To test whether the peas-in-a-pod pattern was real, I concocted (on my
> laptop) imaginary planetary systems in which the sizes of planets orbiting a
> given star were random. Could some sort of bias in Kepler’s method of
> finding planets—which favors the detection of large planets close to their
> stars—contrive to make the planets in each of my imaginary systems appear to
> fit the pattern?_

> _The answer was no: in more 1000 trials with randomly assigned planet sizes
> put through a virtual Kepler’s detection scheme, a pattern of similarly-
> sized planets in the same systems never emerged. This computational
> experiment did not reproduce what we observe in the Kepler planetary
> systems. Thus, the regular sizes of planets is a real astrophysical
> pattern._

This is actually a really cool use of computer simulations that I haven't
noticed before (but I'm sure has been done in the past): simulating expected
output for a known bias.

I wonder if it would be feasible to do the reverse too for a kind of parameter
fitting to fix our model:

1\. Create a reasonable approximate model for both Kepler's expected detection
bias and for planet size distribution.

2\. Constrain parameter space for these models as much as possible, to
minimize the search space.

3\. Using these models, generate a set different planetary sets for different
parameters.

4\. Find the outputs with the closest match in statistical "shape" of the
actually measured data.

5\. generate new input parameters based on these output that lead to set
outputs to refine shape until certain level of matching has been found

If done naively this would probably take a lot of computation and result in
large a solution space: the more parameters, the higher the conditionality of
this space. So the models should be approximations with as few parameters to
produce reasonable results, and with constraints on said parameter values
based on known physics. This would narrow down both the parameter space to
search the possibly valid outputs of this space.

Based on these parameters differ from the output we had expected before, we
might then get a direction of where to look for the physics that _does_
explain the distribution.

~~~
21
This kind of stuff is regularly done at LHC - they simulate the detectors and
the collisions, and then compare real data against that, to both confirm that
the detectors are working properly, and for searching of new physics.

~~~
jlj
Also in the LIGO project, it's a branch of astrophysics called numeric
relativity. The gravity wave signatures predicted by the simulations was what
helped confirm the LIGO detections of black hole and neutron star mergers.

[https://en.m.wikipedia.org/wiki/Numerical_relativity](https://en.m.wikipedia.org/wiki/Numerical_relativity)

------
irrational
So, the Kepler method of detecting planets only works if the orbital plane
(maybe not the right term) of the star we are looking at is such that the
planets are between us and the star, right? So if we are looking down at the
"top" of the star then no planets will obscure the star, right? Also the
planets need to be passing in front of the star at precisely the right time
that the planet and star and our telescope are all lined up more or less.
Someone looking at our solar system would need to wait quite awhile to see
Pluto pass by. If all of that is correct, how are we able to see any
exoplanets? My layman's guess would be that it would be incredibly unlikely
that everything would line up so that we could see anything. What am I missing
in this picture?

~~~
gmiller123456
There are several methods of detecting exoplanets[1], the method you're
referring to is the easiest and is called "transiting". Since it's the
easiest, most exoplanets have been discovered with this technique. As you've
guessed, it is highly unlikely for the stars and planets to align this way,
and the general hypothesis as to why we've discovered so many is that there's
a lot of planets out there[2].

[1]
[https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanet...](https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets)

[2]
[https://www.nasa.gov/home/hqnews/2013/feb/HQ_13-057_Kepler_T...](https://www.nasa.gov/home/hqnews/2013/feb/HQ_13-057_Kepler_Tiny_Planet.html)

------
thrower123
I don't stay up on the latest developments in this field day to day, but my
understanding is that most of the extrasolar systems that we can observe are a
little on the wonky side to begin with, otherwise we wouldn't be able to
detect that there are planets in them at all. Super-Jupiters orbiting close
enough to make their stars wobble, binary star systems, all kinds of stuff.
I'm not sure I'd hazard a guess at any kind of definite conclusion at the
makeup of the universe and our overall specialness in it, with tools of
observation as crude and limited as we've still got; there's a long way to go
just to survey what is out there.

~~~
dwaltrip
I believe the article attempts to account for your concern.

~~~
orbitingpluto
Humanity has only been searching for exoplanets for a very short time. That's
why there are relatively few candidates farther than 1 AU out. It's somewhat
like arguing that all lattes are comprised of milk only because we've only
taken the first sip.

~~~
spectre256
I'm not sure why you were downvoted, that's a beautiful analogy.

------
Symmetry
That's pretty comforting. As the solar system we live in seems more unusual it
seems more credible that planets with advanced life might be rare. In which
case the emptiness of the galaxy seems more explicable.

~~~
jerf
Putting the Great Filter not merely behind us, but _way_ behind us, would be a
pretty cool scientific result.

~~~
kijin
There may be more than one Great Filter. We could have passed one of them, but
we might not survive the next one.

~~~
jerf
The point of the Great Filter argument is that something seems to be
preventing widespread intelligent life. If the Filter is behind us, then while
that is not _proof_ that there are no impassible obstacles in front of is, we
have _no particular reason_ to believe that there are impassible obstacles in
front of us. That is in stark contrast to what has been the scientific dogma
for the past several decades, which is that there is nothing special about us
whatsoever, which _does_ give us reason to believe there are impassible
obstacles in front of us. To be able to put the filter way behind us is still
a real change.

~~~
dwaltrip
It depends on how fully the initial Great Filter explains the lack of observed
exolife. It may not be a binary thing.

------
jvanderbot
So to test for unknown bias and sensor anomalies, they put raw modelled data
through the statistical machinery looking for homogenized outputs.

This strikes me as wrong. If you want to know if your filter is bad, you plug
in ground truth and add known noise models. If you want to know if your noise
models are wrong, you cant do the same thing, you need to point your sensor at
a known object (e.g. calibrate).

They seemed to have done a cursory analysis of the former type, which is not
the same as saying "our pea-pod hyoothesis is correct".

~~~
dnbgfher
I don't believe this was an attempt to find bias or noise from the physical
sensors, but rather was looking at the method itself.

The method has some known biases that they were ensuring wouldn't explain the
given pattern in the data. Depending on the depth of the simulation, it may
have also been able to account for some unknown biases in the method.

Now even under your interpretation, I'm curious about which known object you'd
suggest they use.

------
karol
As a side note, the drawing attached to this article is of Edward Tufte's
quality, so much information condensed into a simple-looking drawing and it's
so easy to get the idea from a single glance.

~~~
lolc
I'm actually pretty confused by that chart because the bigger planets of SOL
are off the side.

~~~
DavidSJ
The planets detected by Kepler will tend to be unusually close to their star
due to its detection method. I believe that’s why Sol looks like an outlier in
that regard — it’s really that the other systems are the outliers.

~~~
lolc
Could be. Detecting smaller planets further out is less and less likely.

------
ryanackley
My first thought is this should call into question the method(s) we are using
to measure and observe planets in other solar systems.

Think on this, the one solar system we can empirically confirm with multiple
observation techniques, i.e. we've sent satellites to other planets in, is way
different than solar systems we are observing by measuring light differences
from light years away.

~~~
0-_-0
Yes but the solar system is a biased sample: life evolved in it. Maybe it was
helped by Jupiter shielding us from asteroids that could wipe out life on the
planet? If it's statistically more likely that intelligent life evolves in a
system with large planets then we would expect to see a difference between our
solar system and others that we observe.

~~~
kamaal
All asteroid crashes aren't equal. Earth got most of its water from an
asteroid crash.

Basically a huge of range of things have to work on large timescales for
intelligent life to evolve on a planet.

Which is why intelligent life apart from us could just be absent or very very
rare and far away.

~~~
0-_-0
My point is that a large planet in the system reduces the probability of large
asteroid impacts later in a star system's history. I didn't mean that it
immediately removes all asteroids from a star system after forming.

~~~
hypothete
The "Jupiter as a shield" hypothesis has been questioned recently:
[https://phys.org/news/2016-02-jupiter-role-planetary-
shield-...](https://phys.org/news/2016-02-jupiter-role-planetary-shield-
earth.html)

~~~
0-_-0
That's fair enough, the point I tried to make is: Statistically, we would
expect our solar system to be average among solar systems that can support
intelligent life, not among all solar systems (following the Anthropic
Principle). Therefore, the difference we see between our solar system and the
average star system might imply something about what kind of conditions make
intelligent life more probable in a star system.

If we see that in all star systems we know that evolved intelligent life (even
if there's only 1 we know of) there is a large Jupiter-like planet, and that's
very atypical among star systems, that suggests that Jupiter might have
increased the probability that intelligent life evolved here.

------
majia
> The answer was no: in more 1000 trials with randomly assigned planet sizes
> put through a virtual Kepler’s detection scheme, a pattern of similarly-
> sized planets in the same systems never emerged. This computational
> experiment did not reproduce what we observe in the Kepler planetary
> systems. Thus, the regular sizes of planets is a real astrophysical pattern.

Any explanation to this? I'd assume small planets are just harder to detect.
Large planets could be gas giants that react differently to our observation
technique. Also they tend to form further away from the star, leading to a
longer orbital period and fewer observations. Could these contribute to an
observation bias and does the simulation include these factors?

~~~
shusson
Yeah I don't like the finality of the statement the `answer was no`. Couldn't
the simulation (virtual Kepler’s detection scheme) simply be incorrect?

~~~
unparagoned
Anything is possible. You can never prove anything. In science/real life true
means very likely and false means very unlikely. So yes the simulation could
be wrong, but I guess with everything we know and the error bars the answer
was clearly no.

------
netcan
Fascinating stuff. ..and all deduced from the slightest dimming of starlight
hundreds of light years away. Badass.

------
perseusprime11
The thought of we may be the only species in the Universe scares me. And, we
don't have a great insurance policy.

~~~
nikbackm
Why?

All of us living now will be long dead before our species die out, so what
difference does it really make?

~~~
mrkstu
Because if we're the only one's actually capable of appreciating the beauty of
the universe, if we are in actuality the only mindful expression of the
universe, we are more incomparably valuable than any other element existing as
part of that universe, and an irretrievable loss once gone.

~~~
thfuran
Why is perceiving beauty so valuable? It does exactly nothing except for the
one perceiving.

~~~
TuringTest
That's why it's valuable. _To us._

~~~
Atlantium
When this species becomes capable of observing our feelings objectively and
not simply saying "I feel it, it's mine so it must be truth" people like you
are going to feel something very different.

~~~
TuringTest
Truth != value. Of course my feelings are valuable to me; I don't need them to
be true (and I don't even think being true or false _applies_ to judgement
values).

 _" I once heard a wise man say that if anyone were to know the whole answer,
he would cease to exist."_

[https://books.google.es/books?id=KuFwDwAAQBAJ&lpg=PT181&ots=...](https://books.google.es/books?id=KuFwDwAAQBAJ&lpg=PT181&ots=z2ut_ZFt-o&dq=%22I%20once%20heard%20a%20wise%20man%20say%20that%20if%20anyone%20were%20to%20know%20the%20whole%20answer%2C%20he%20would%20cease%20to%20exist.%22&pg=PT181#v=onepage&q=%22I%20once%20heard%20a%20wise%20man%20say%20that%20if%20anyone%20were%20to%20know%20the%20whole%20answer,%20he%20would%20cease%20to%20exist.%22&f=false)

------
xen2xen1
Random question.. If they are looking for transits, doesn't that presuppose
the data will find close in planets? I believe that's not the only method, but
wouldn't that push more close planets than distant ones? Would it find
transits of things like Neptune or Uranus that take hundreds of years?

------
dugluak
apologies if this is a stupid question, but I always wondered can there be
multiple objects/planets in an orbit?

~~~
hoorayimhelping
Not a stupid question at all. The answer is: yes.
[https://en.wikipedia.org/wiki/Trojan_(celestial_body)](https://en.wikipedia.org/wiki/Trojan_\(celestial_body\))

Theories for the formation of our moon suggest a Mars-sized Trojan collided
with earth before it was earth:
[https://en.wikipedia.org/wiki/Theia_(planet)](https://en.wikipedia.org/wiki/Theia_\(planet\))

------
lolc
Can anybody explain why the chart stops at 3 AU? All our bigger planets are
off the chart.

~~~
itronitron
Seems likely that the planets with larger orbits have not yet been detected
since they will take longer to reach a point in orbit when they are transiting
their respective stars. It seems premature for the paper to reach it's
conclusion when Kepler has been in operation for less than ten years, but
hey... publish or perish.

------
ncmncm
This result says that random sizes and orbits are not consistent with
observations. But there is a huge gap between "random" and "uniform", even
ignoring all the possible different distributions.

We know that our solar system is not random -- e.g., we have the "platonic
solids" spacing, for our inner planets. So, our solar system is also not
described by the disallowed model.

It's great that some subset of random distributions are ruled out for systems
that happen to have planets packed close to their star, but that says nothing
at all about how we compare to the the overwhelming majority of other systems
systematically excluded from the sample.

As with most results that hit the popular press, any actual significance is
garbled to the point of meaninglessness.

But a good graphic can be worth a lot if you ignore the headline.

------
yaya69
[https://en.wikipedia.org/wiki/Axis_of_evil_(cosmology)](https://en.wikipedia.org/wiki/Axis_of_evil_\(cosmology\))

------
qubax
Stranger? We already knew our solar system was strange. At least compared to
the other solar systems we observed ( admittedly a tiny fraction - a couple
hundred out of 200 billion solar systems ).

We already knew gas giants ( a major cause of our peculiarity ) are rare. And
we knew that most solar systems had uniform sized planets ( within a
particular range ) orbiting very close to their suns.

The article doesn't offer anything new that would make us think the solar
system is stranger. It just reaffirms everything we knew and why we thought it
was strange to begin with.

------
sidcool
I am fascinated about how less we know overall about the earth, and the solar
system. I would not be surprised if we found life in the solar system. May not
be advanced, but multi cellular life. I mean life as it was on earth some
10,000 years ago, with early humans and all.

Edit: Sorry I shared my fictitious fascination. It would probably make a good
movie, humans finding pre-historic humans on Titan or Europa.

~~~
contravariant
I would be surprised if even our concept of cells translates that easily.

Unless of course both forms of life share the same origin, but that just
raises more questions.

~~~
TangoTrotFox
This is the thing I also always wonder about. Consider that about 60% of a
banana's DNA is shared with us. And for cats it's 90%. That's just really
stupefying to think about. But the more important point here is that I think
it is literally impossible for us to even imagine what life that had no
genetic similarity to us would even begin to be like. We just have no basis
for comparison whatsoever since we are all so closely related.

Though yeah, genetic similarity implying exogenesis would also be an equally
interesting result. Would that similarity be organic/natural in nature, or
might we just be some species' lab experiment? Perhaps they seeded us with
their same genetic origins to discover more about their own evolution and
development. This is an experiment I'm certain we'll eventually carry out
ourselves. So many interesting possibilities.

~~~
saalweachter
So there's two high-confidence bets we can make about alien life:

(1) They will probably share huge swaths of the basic chemistry and machinery:
proteins, sugars, starches, fats, and even more surprising things like cell
walls and digestive acid and (something like) DNA. The building blocks of life
are basic chemistry, and are some combination of "the simplest possible
molecule that can do a thing" and "things that arise naturally from inorganic
processes".

(2) There will almost certainly be 0% overlap in terrestrial and alien DNA,
even assuming aliens use DNA and use the same four amino acids to encode their
DNA and even assuming they have identical proteins and cellular structures.
This is because the encoding from DNA to proteins is more-or-less arbitrary,
and determined by both the exact cellular machinery used to turn DNA into
proteins and by our genetic history. Even in our own cellular machinery,
different DNA sequences can code for the same protein, so you can encode any
individual protein in a bajillion different ways. The _only_ real reason for
to different organisms to share any common DNA sequences is because they both
derive from a common ancestor. If our DNA and alien DNA overlap in _any_
meaningful way, even with the tiniest of percent, it's basically conclusive
proof of exogenesis of some sort.

So basically, it is very likely we'll be able to eat aliens (probably no more
or less likely than how likely it is you can eat any particular plant or
animal on Earth, to be honest), and almost impossible that we could ever
hybridize alien and terrestrial plants and animals.

~~~
openasocket
I think it goes further than that, that alien and native lifeforms will
probably be toxic to one another. All life on this planet evolved in tandem,
and have some of the same basic compounds for life, so there are few toxic
interactions between life forms, excluding those evolved for defense (and even
then there are exceptions, plenty of plants contain. And even then there are
plenty of exceptions. But lifeforms from a completely different evolutionary
line may use completely different proteins for basic functions. Even using the
same proteins but of the opposite chirality could result in toxic reactions.

I think that even if we found alien life that evolved and developed on a
planet much like ours, and used the same amino acids, metabolic processes, and
cellular structures, the odds are high that contact with them would result in
toxic interactions.

~~~
saalweachter
You've got to weigh "we didn't evolve to specifically eat it" against "it
didn't specifically evolve to prevent us from eating it". I'm not sure we'll
get an answer to which is a bigger factor unless we find some xenobiology and
take a bite.

A lot of digestion is pretty elementary, and built upon our stomachs' acid
bath -- proteins go in and are unwound and broken down. Most foods that cause
problems later down the line contain a protein that both (a) is resistant to
the stomach acid, and doesn't break down before hitting the intestines and (b)
causes a problem when it hits the intestines.

Barring that - or incorporating elemental poisons like arsenic at levels we
can't cope with - I'd personally bet that if you charred a random alien
critter over a fire and wolfed it down, it's not crazy that your stomach acids
would break down anything that survived the fire and would otherwise harm you,
and you'd be able to extract a reasonable mix of sugars, fats and proteins
from what you'd ate.

It's not impossible that an entire planet would have some proteins common to
all of their lifeforms that both (a) didn't break down easily when cooked or
digested and (b) were incredibly lethal to terrestrial life, but there's no ab
initio reason to think they would or wouldn't, one way or the other.

~~~
openasocket
The stomach isn't a perfect barrier, there's always something that gets
through. If it didn't we wouldn't be able to take drugs orally. Our bodies
have an entire subsystem devoted to processing compounds that made it through
the main digestive system into the blood stream. The liver is dedicated to
metabolizing these substances, in a process literally called "xenobiotic
metabolism".

Sure, the odds of a particular compound found in some alien lifeform having a
toxic interaction with our bodies is small, but I consider the odds of one of
the hundreds of thousands of different types of compounds in that lifeform
having a toxic interaction is on the higher side.

Oh, and to be clear, by toxic interaction I don't necessarily mean a poison,
per se. It could also have a carcinogenic effect, or if the compound is common
enough in the creature and undigestable through the stomach and intestines it
could overload the liver, etc.

~~~
saalweachter
Yeah, not a perfect barrier, but if it's good enough that I'm not poisoned, do
I care? I eat lots of delicious food that doesn't digest optimally.

As for carcinogenic effects, well, depends on what the timelines and cancer-
rates you're talking about look like. We eat lots of things on Earth that are
mildly carcinogenic over a lifetime, and the fact they are doesn't really stop
us.

------
ncmncm
Not convincing.

We know Kepler results are heavily biased for (1) systems edge-on to us (2)
with big planets (3) very close to their star.

The only conclusion to draw is that planets that are all clustered close to
their star tend to similar sizes. Then only Mercury is unusual. Even there,
it's not unique.

Stars with planets distributed more widely, like ours, have been
systematically filtered out of the results. We have no idea how common they
are. It might be that they are rare, and that would make us unusual. In that
case, distribution would be interesting and relative sizes would be
unremarkable.

If in fact they are common, there is no reason to expect sizes in those cases
to be uniform.

A system that condensed from a cloud with less intrinsic rotation seems more
likely to have its planets clustered close. Less intrinsic rotation could also
result in more uniformity.

~~~
vanderZwan
> _We know Kepler results are heavily biased for (1) systems edge-on to us (2)
> with big planets (3) very close to their star._

This article was written by an astronomer working with Kepler, and I wonder
why you apparently seem to believe that they are so naive that they forget
about the bias in their own research tools.

Furthermore, the article explicitly mentions this issue, and provides an
explanation for why they believe it does not apply, making me wonder if you
read it at all:

> _I concocted (on my laptop) imaginary planetary systems in which the sizes
> of planets orbiting a given star were random. Could some sort of bias in
> Kepler’s method of finding planets—which favors the detection of large
> planets close to their stars—contrive to make the planets in each of my
> imaginary systems appear to fit the pattern? The answer was no: in more 1000
> trials with randomly assigned planet sizes put through a virtual Kepler’s
> detection scheme, a pattern of similarly-sized planets in the same systems
> never emerged._

Unless you have a reason to dispute this method of verification of course, but
then you should share that.

I personally see no problem: the claim is implicitly that since the measured
data does not match the predictions of the model, the model is wrong. The
model + known bias of Kepler is used in simulation to generate expected
statistical output of measured data sets. The generated data does not match
the measured data. Hence, either the model of Kepler's bias is wrong, or the
model of what planetary systems to expect.

Since we based the planetary system model on our own solar system, if that
model is wrong then that makes our own solar system special.

~~~
Lort
>This article was written by an astronomer working with Kepler, and I wonder
why you apparently seem to believe that they are so naive that they forget
about the bias in their own research tools.

Exactly. I actually did some research on Weiss.

So she studied astronomy at Harvard where she got her BS, then went on to
Cambridge for her masters, and then a PhD from Berkeley. Now she works with
NASA.

Odd that all these people who clearly didn't even read the article seem to
find supposedly obvious bias and flaws in the research of someone who is
clearly among the top young researchers/experts in this field.

