ScienceDaily (Aug. 8, 2008) — Prevailing theoretical models attempting to explain the formation of the solar system have assumed it to be average in every way. Now a new study by Northwestern University astronomers, using recent data from the 300 exoplanets discovered orbiting other stars, turns that view on its head.
mgb_phys
Aug13-08, 05:22 PM
On the other hand there is a serious selection effect looking for exoplanets - you only detect the big ones. It's like claiming our galaxy is rare because it's not a quasar.
berkeman
Aug13-08, 05:25 PM
Interesting article. Thanks wolram. I wonder if this will change the calculations for the probability of life elsewhere in the Universe:
Those simulations described in the article would seem to change at least one part of the calculations...
Garth
Aug13-08, 05:48 PM
On the other hand there is a serious selection effect looking for exoplanets - you only detect the big ones. It's like claiming our galaxy is rare because it's not a quasar.
Agreed, the selection effect also picks out planets that are near to their stars, hence the plethora of 'hot jupiters'.
Garth
berkeman
Aug13-08, 05:51 PM
Agreed, the selection effect also picks out planets that are near to their stars, hence the plethora of 'hot jupiters'.
Yeah, but as I read the article, they are saying that their simulations result in fewer solar systems like ours compared to previous expectations. And by the way, that seems to match the exoplanet observations so far. The fact that hot jupiter systems are easier to detect doesn't seem to alter the significance of the simulation results.
Garth
Aug13-08, 06:12 PM
Agreed, but the observations of the known exoplanet systems were used in the simulations.
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, as the planets approach each other, they frequently lock into dynamical resonances that drive the orbits of all participants to be increasingly elongated. Such a gravitational embrace often results in 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."
The question about the simulations with the many non-sedate systems is what happens next?
I have done such simulations with the Jupiter/Saturn Trojan system a long time ago and one factor is the stability of a dramatic system or how it might become stable.
After 5 Gyrs or so the planets on 'exciting orbits' are merged, consumed or ejected from the system leaving just the sedate ones in their (thankfully) boring orbits.
It will be interesting to see what happens when we are able to detect Earth sized planets and the like. Perhaps a few solar system types will be found, and they will turn out to be the older systems (and also homes to ET?....)
We live in exciting times.
Garth
berkeman
Aug13-08, 07:34 PM
Agreed, but the observations of the known exoplanet systems were used in the simulations.
Ah, I missed that part. Thanks Garth. That's kind of worrisome after all, that they are using skewed data to help guide their simulations...
Kurdt
Aug13-08, 08:02 PM
The exoplanet discoveries so far have made us rethink our solar system formation models but as has been mentioned before, there are 'selection effects'. We can only detect massive planets relatively close to their parent stars. Exoplanets are hot property at the minute and there are lots of technologies that will be coming online in the next few years that will allow us to see smaller planets and some that might allow us to analyse the spectra of exoplanet atmospheres (such as DARWIN).
Personally I think its far too early to say we're unique or exceptional in terms of our solar system structure.