New Study Shows Solar System is Unique Monday, September 01, 2008 - Shalhevet Bar-Asher Home >> News >> Space
Research conducted by a team of North American scientists recently claimed that our solar system is special, contrary to the accepted theory that it is an average planetary system. Using computer simulations to follow the development of planets, it was shown that very specific conditions are needed for a proto-stellar disk to evolve into a solar system-like planetary system. The simulations show that in most cases either no planets are created, or planets are formed and then migrate towards the disk center and acquire highly elliptical orbits.
a montage of planetary images taken
by spacecraft managed by the
Jet Propulsion Laboratory in Pasadena,
CA. Included are (from top to bottom)
images of Mercury, Venus, Earth
(and Moon), Mars, Jupiter,
Saturn, Uranus and Neptune.
(Credit: NASA/JPL)
A planetary system consists of various non stellar objects orbiting a star, such as our sun. Over the past several years more and more planetary systems have been discovered, with varying masses, orbits and other system characteristics. Computer simulations attempting to track the development of a planetary system have been restricted due to computational limitations and the complexity of the problem. The new simulation is the first that is able to track planetary systems, beginning with the disk of gas and dust left behind after the formation of the central star and ending with the planetary system.
The research was aimed at finding the connection between the properties of the proto-stellar disk and those of its progeny, the planets. A set of 100 simulations, based on data from over 250 planetary systems and spanning 500 million years, was carried out, covering a range of parameters. The two main parameters were the initial disk mass and its viscosity, which determines the rate of gas accretion onto the central star.
The simulations show that the proto-stellar disk pushes the planets towards the star. As the planets approach each other, their interaction often results in an elongation of their orbits. Occasionally the outcome of these interactions is the flinging of a planet to a different location in the system, or even into deep space. Eventually the gas in the disk is all consumed and the planetary system emerges.
Due to the complexity of the developing system, which includes the disk-planet and planet-planet interactions described, the simulations resulted in random systems. Nevertheless, two dominant cases were detected.
In a disk with low mass and high viscosity, the gas in the disk is removed before a planet can form, resulting in a system that has only rocky, icy bodies. At the other end, in a disk with high mass and low viscosity, planets are formed but are pulled towards the center of the system and acquire highly elliptical orbits around the star.
In the intermediate case, planets form but undergo only modest migration towards the star and their orbits don't become as elliptical. This seems to be the case of the solar system. The simulation showed that this case is realized in a small number of systems, meaning the solar system does not resemble most planetary systems.
One of the scientists who conducted this research, Frederic A. Rasio from Northwestern University in Illinois, said: “We now better understand the process of planet formation and can explain the properties of the strange exoplanets we’ve observed. 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.”
Shows Solar System is Unique (09/02/08 - 8:56 - by Edwin Reeves)
The title of this article is so bizarre as to call into question the editor's understanding of the scientific method. This study shows nothing about exosolar planetary systems. It suggest, using simulations based on inferred indirect data, that the solar system in not the norm. Have the standards of proof really sunk so low?
yeah? really? (09/02/08 - 9:45 - by anti-thisarticle)
data based on 250 planetary systems? yeah, right. theyre seriously gonna go and say that the systems they observe here are going to be under the same conditions somewhere else in the universe or in another universe altogether. nice one "north american scientists" now we look that much stupider
initial conditions (09/02/08 - 9:53 - by Roland)
The problem with these simulations is that we know small differences in initial conditions can have large effects, and we are not sure about those initial conditions. Also, tidal forces can move bodies out, and circularize orbits, as with earth/moon. Is that factored in these simulations?
Unique ?!? (09/02/08 - 10:59 - by Russ)
Unfortunate use of that word, given the content of the article. "Special" would surely be better.
Sheesh. (09/02/08 - 20:44 - by nighthawk808)
In November 1903, a mathematical proof was given for why heavier-than-air craft are impossible. Need I remind anyone what the Wright Brothers did the very next month?
In the 1940's, dozens of scientists "proved" that it was impossible for anyone to go faster than the speed of sound. In 1947, Chuck Yeager did just that.
Around 5 billion years ago, the Solar System was formed. Yet these guys have just "proved" that it can't happen. At least the two examples I gave above had the excuse of never having had the phenomenon they "disproved" happen before then. Rasio et al. can't claim the same ignorance.
I look forward to their follow-up which proves that electricity cannot be harnessed to perform computations.
You're actually wrong. :\ (09/02/08 - 23:28 - by Uhh)
I can say that because it's not a matter of opinion. It's fact.
You said they proved it *can't happen* when they actually said "it's unlikely but it happens sometimes"
:\
reply to Uhh's comment (09/03/08 - 9:36 - by Shalhevet Bar-Asher)
I actually never used the words "can't happen", on the contrary it says "The simulation showed that this case is realized in a small number of systems".
Rasio et al should be ashamed. (09/03/08 - 9:46 - by Chad)
This is the science equivalent of looking at a glass of water and predicting oceanic currents.
First off, every planetary system is going to be unique (just like people). Second, we don\'t have anywhere NEAR enough data to make good simulations. Heck, 20 years ago they were confident planets would be unlikely outside Sol - and now we find them everywhere.
This ultimately reeks of modelers avoiding science and stoking their egos.
Biased (09/03/08 - 14:49 - by Krommeman)
Data of exotic planetary systems give exotic results. We have just begun discovering planetary systems. The ones we have detected have been detected because of their bizarre properties.
It's in Science, guys (09/04/08 - 10:19 - by Rich Deem)
You may not like the implications of the study, but it follows the trend of the last few years showing that our solar systems is not just run of the mill. The article is published in Science, the premiere, peer-reviewed scientific journal (see http://www.sciencemag.org/cgi/content/abstract/321/5890/814). Get over it!
