Our Solar System: An Island of Calm in a Violent Universe (and it's special, too)
Written by Nancy Atkinson
We humans like to think we're special, but astronomically speaking we've been shot down quite severely and humbly put in our place. We're not at the center of our solar system, nowhere near the center of our galaxy and certainly not at the center of the universe. But now comes great news for the human psyche from scientists trying to explain solar system formation. As far as solar systems go, we have thought ours was just average and that all solar systems were like ours. But in looking at the 300 plus extrasolar planets that have been discovered and the systems they are in, none so far are anything like our home solar system. In fact, say scientists at Northwestern University, we may be special after all. In a study using computer simulations (this is the week for computer simulations, see here and here), researchers ran more than a hundred simulations, and the results show that the average planetary system's origin was full of violence and drama but that the formation of something like our solar system required conditions to be "just right" and quite special indeed.
The study illustrates that if early conditions had been just slightly different, very unpleasant things could have happened — like planets being thrown into the sun or jettisoned into deep space. This was the first simulation to model the formation of planetary systems from beginning to end, starting with the generic disk of gas and dust that is left behind after the formation of the central star and ending with a full planetary system.
Before the first exoplanets were discovered in the early 1990's we only had our own solar system from which to create a model, and astronomers had no reason to think our solar system unusual.
"But we now know that these other planetary systems don't look like the solar system at all," said Frederic A. Rasio, a theoretical astrophysicist and professor of physics and astronomy at Northwestern.
"The shapes of the exoplanets' orbits are elongated, not nice and circular. Planets are not where we expect them to be. Many giant planets similar to Jupiter, known as 'hot Jupiters,' are so close to the star they have orbits of mere days. Clearly we needed to start fresh in explaining planetary formation and this greater variety of planets we now see."
The simulations suggest that an average planetary system's origin is extremely dramatic. The gas disk that gives birth to the planets also pushes them mercilessly toward the central star, where they crowd together or are engulfed. Among the growing planets, there is cut-throat competition for gas, a chaotic process that produces a rich variety of planet masses.
Also planets orbiting close to each other can create a slingshot encounter that flings the planets elsewhere in the system; occasionally, one is ejected into deep space. Despite its best efforts to kill its offspring, the gas disk eventually is consumed and dissipates, and a young planetary system emerges.
"Such a turbulent history would seem to leave little room for the sedate solar system, and our simulations show exactly that," said Rasio. "Conditions must be just right for the solar system to emerge."
Too massive a gas disk, for example, and planet formation is an anarchic mess, producing "hot Jupiters" and noncircular orbits galore. Too low-mass a disk, and nothing bigger than Neptune — an "ice giant" with only a small amount of gas — will grow.
"We now better understand the process of planet formation and can explain the properties of the strange exoplanets we've observed," said Rasio. "We also know that the solar system is special and understand at some level what makes it special."
"The solar system had to be born under just the right conditions to become this quiet place we see. The vast majority of other planetary systems didn't have these special properties at birth and became something very different."
So, go ahead. Feel special.
Original News Source: Northwestern University
Filed under: Astronomy
August 7th, 2008 at 4:46 pm
"But we now know that these other planetary systems don't look like the solar system at all," said Frederic A. Rasio, a theoretical astrophysicist and professor of physics and astronomy at Northwestern.
"The shapes of the exoplanets' orbits are elongated, not nice and circular. Planets are not where we expect them to be. Many giant planets similar to Jupiter, known as 'hot Jupiters,' are so close to the star they have orbits of mere days. Clearly we needed to start fresh in explaining planetary formation and this greater variety of planets we now see."
Isn't the preponderance of hot Jupiters observed entirely explicable by the bias inherent in the Doppler wobble technique used to detect the vast majority of exoplanets? Obviously close-orbiting massive planets have the greatest effect on the velocity of the primary star, so that's what we see most of. I hope theoretical modellers aren't jumping to unwarranted conclusions about the likely true population of size/mass planetary distributions.
August 7th, 2008 at 5:17 pm
Agreed. I think the article reads as though it were "natural" for other solar systems to form they way we've observed. It's not.
It's natural that we've discovered so many hot Jupiters because our observational methods are currently too primitive to see the other solar systems that are very similar to ours.
In fact there is one solar system which was discovered with gas giants in roughly the same place as Jupiter and Saturn.
But of course we can't detect terrestrials very easily yet, so we don't know about anything closer in to that star. But it could have 4 terrestrials and be basically exactly the same as our solar system for all we know.
August 7th, 2008 at 8:20 pm
Right now there's too much observational bias to make an informed decision.
Not enough data.
Still, it its interesting.
August 7th, 2008 at 9:43 pm
I hope that once we've found better techniques to search for extrasolar planets we find that we're not all that special. The less common a solar system like ours is, the less common life like ours will be. A diverse galaxy full of varied life forms makes for a much more interesting interstellar war, which I believe is what all of us nerds are really looking forward to. =D
August 8th, 2008 at 12:39 am
Special or not, maybe it's time we started looking after the place.
Hopefully, if observational techniques improve, we may be able to detect smaller exoplanets, including terrestrial ones.
August 8th, 2008 at 12:47 am
All the boys are right. It is still too early in the game to say that "We're special".
Once we really get the technology to study other solar systems, we'll probably find lots of them that are like ours.
August 8th, 2008 at 2:23 am
I don´t agree at all with this perspective that presumes that our solar system is something very special, because we know 300 diferent stars and their process of creation was to violent and so on. We know a few 300 stars with planets in this unmesurable cosmos. How can we assume that the other billion of billion of billion of star that exist are like the 300 stars with planets that humans know? It is not a relevant number, in my point of view. We need a more profund knowledge of universe to presume this kind of things. There nothing special in our solar system, at least at this moment, because we don´t have a reasonable number of other solar systems to compare with our own.
August 8th, 2008 at 6:14 am
It's exactly the same reasoning that presumes global wa…er…ah…, that is, I mean…climate change must be caused by human activity, based on an extremely primitive computer model that has the biases of the code writer built in, deliberately or not, and that in retrospect, fits a few, but not even most, of the data points of past observations.
The universe, like climate on earth, is so big and complex as to be far beyond our understanding at this stage of our intellectual development. It is the height of hubris to be speculating that we "know" anything for certain at this point. Everyday it seems, something we discover astounds, amazes and mystifies us.
I'm glad that most astronomers and other hard scientists still keep an open mind regarding the accuracy of these so-called "simulations", unlike many of those who create the models in the multi-billion dollar climate change industry.
August 8th, 2008 at 7:20 am
"Yes, this a classic case of limited conclusions born from limited data"
but still there's no reason to get hostile guys there doing the best they can with what they have. If you feel so strongly about it come up with a better technique.
August 8th, 2008 at 7:58 am
Just curious. How do we know we are "certainly not at the center of the Universe."? Thank you.
August 8th, 2008 at 8:12 am
Its funny, a long time ago many people believed our planet and its solar system is special. Now, many people don't think it is special.
To me, the idea that our planet is not special, just average in someway, is as much of a preconcieved notion as the assumption of "specialness". Maybe the ideas have different starting points, but they seem to me to be based on what we want to be than what is.
I think the interesting point of this article is that astronomers are looking at various solar systems and finding that they are not what was expected. And this is causing them to re-evalute their theories on solar system formation. Now, they are not so certain our solar systems development is normal. Thats cool. That's science.
So let me be presumptive and state that this planet is special. Its the only one we know for sure exists that has the right conditions for our form of life. One day should we find another solar system like ours, then it can be special too. I think its too early to say we are not special. You can expect to find other systems like ours, but until they are found - we're it.
August 8th, 2008 at 9:15 pm
Is that Pluto I see sitting out there at the end? I still like thinking of it as a planet. Glad somebody else does, too.
August 9th, 2008 at 12:24 am
This is all based on our perception of the here and now. We don't know how many "planets" there were and what our solar originally looked like. We only look for life in the parameters we define, then call our environment special because we evolved from it at a certain point in time. We may indeed be alone in the universe unless we can redefine what can be considered as life, and if so what can be gained from it's discovery.
August 9th, 2008 at 11:22 am
Absolute codswallop, this article is misleading nonsense.
August 9th, 2008 at 3:52 pm
Without going into any "creation theory" or "evolution theory" (and evolution IS still just a theory) it would not surprise me that in the timeline that intelligent man has existed and will continue to exist, we never, ever, discover life outside of our own little planet! We may find organic microbes living in extreme conditions elsewhere in our solar system, but is that really life? How about beings with the ability to think and reason? Think of the incredible coincidences that have had to all come together to produce life (and intelligence) as we know it. A few hundred thousand miles from a different orbit or no moon or smaller or bigger sun, earth's rotation and gravity, atmospheric composition, etc. Traditional thought is the "BIG BANG THEORY." OK, let’s say we have all the parts for a fine watch, all in pieces. How many times would we have to blow these pieces up until they come together, on their own, to form, what might even closely resemble a watch? How about a billion billion times? Or NEVER? Is this the same as saying that our little earth came together the same way? We also forget to include time as a function of existence. Who’s to say that a million earths have existed since time began? We could be truly unique in this universe at this time or ever. However, if we aren't alone, are the distances so vast that we will never know if life and intelligence exists beyond what we will ever be able to discover? If we are alone, I'm OK with it, if we aren't alone, I'm OK with that too, because it will NEVER concern us due to the unimaginably vast distances that separate potential solar systems like ours. Live Long and Prosper (and be lonely?)
August 10th, 2008 at 9:57 pm
We live on a planet in a galaxy in a Universe that is friendly to our DNA type of existence. Of course there is life out there. It's mandatory.
Intelligent life may be few and far between, but people of this century will likely never know or be able to respond to the noise of other technological civilizations. Civilizations such as ours may not last long enough to exchange information over the vast amounts of time required.
August 10th, 2008 at 11:55 pm
A little whimsy to help the day go by
"Just remember that you're standing on a planet that's evolving and revolving at nine hundred miles an hour, that's orbiting at nineteen miles a second, so it's reckoned, a sun that is the source of all our power.
The sun and you and me and all the stars that we can see are moving at a million miles a day, in an outer spiral arm, at forty thousand miles an hour, of the galaxy we call the "Milky Way".
Our galaxy itself contains a hundred billion stars. It's a hundred thousand light years side to side. It bulges in the middle, sixteen thousand light years thick, but out by us, it's just three thousand light years wide.
We're thirty thousand light years from galactic central point We go 'round every two hundred million years, and our galaxy is only one of millions of billions in this amazing and expanding universe.
The universe itself keeps on expanding and expanding in all of the directions it can whizz as fast as it can go, at the speed of light, you know, twelve million miles a minute, and that's the fastest speed there is.
So remember, when you're feeling very small and insecure, how amazingly unlikely is your birth, And pray that there's intelligent life somewhere up in space,
'Cause there's bugger all down here on Earth."
August 11th, 2008 at 10:36 am
Whoever said ours is not a special place in the universe is wrong. Just as each one of us out of the 6 billion people on this planet has a unique face and identity so must be true for our solar system and earth too.
But what of it…I'm not glad if our place, this earth, is unique or not, I'm just glad and pray for it to continue to exist… for one thing i know too well that nothing is permanent…unique or not.
What was once unique is now no more…seems more like the universal law that governs everything around us.
August 12th, 2008 at 7:11 am
While I would agree that this Planet Earth is a sacred and beautifully 'unique' place, I would suggest your title should really have had a question mark after it.
that are flying about and causing they're share of turbulence and ongoing damage.
Perhaps the Galaxy or the Universe is in many ways extremely turbulent, but our Solar System and even the near Earth area is anything but 'calm'…ever. Our Solar System has been pretty beat up over the ages with a number of bodies here tipped over and some with other obvious signs of severe damage from the 'cycles of bombardment'. Impact wise, the single largest known crater in our Solar System at this time is located right on our own Moon. The Aiken impact on the South back side. Earth which heals fairly nicely overtime still reveals to us about 160 know impact craters.
Better yet, the recent milestone for SOHO comet discoveries revealed in a news piece that 85% of the all known comets come from a single Super Comet that was destroyed in a death spiral into the Sun. Known as the Kreutz Sungrazer Group, one starts to see the level of spin off comets and subsequent 'debris fields'
So, while I enjoyed your article I pleasantly would like to differ with you on the premise of a 'calm island in the storm'.
August 12th, 2008 at 3:42 pm
Boni says.
To Red Dog:
How do we know we are "certainly not at the center of the Universe."?
Ans. Because the Universe has no center .
Nobody is at the center of the Universe the same way nobody on Earth is at the north o f North pole.
Space and Time were created with the Universe no in the Universe,..
If no matter ( or Energy ),.., no space and no time. Not an empty space waiting to be filled , not a time passing, waiting for a clock to be counted. CERO,..NOTHING.
August 12th, 2008 at 4:14 pm
About our Solar System being special because we didn't find one alike in 300 stars close tu us…
The ausence of evidence IS NOt evidence of ausence or…presence.
It means Nothing.
This sound a little "Intelligent Design advocation"
Our galaxy has around 400 Billions stars, and the observable Universe has around 100 Billions galaxies . If only 100 billions stars is the average ( There are some with tens of Trillions like M-87 ),..the Observable universe has 10 ^ 22 ( 1 with 22 ceros ) stars, and that is more stars than grains of sand are in all beaches of the World ( Carl Sagan " Cosmos" Pag. 196.) If we some day can find one like us and with intelligent life, that is the Question,..could be tomorrow, could be in 1 billion years ( if we are here,..say our evolutioned decendant s natural or artificially,..),or never.
By the way; It is time for us. to take Evolution in our hands, like we do already, with animals and plants to adapt an improve it,..
( I know some people is going to get mad at me because this, Welcome.)