Extra Solar Planets, a few questions.

[Apollo7]

Ok, maybe you guys can fill me in a bit here. I've been looking at the Extra Solar Planet Encyclopedia and I've been curious as to the configurations of these systems.

Really my main question is as follows:

Since the current crop of extrasolar planets tends to reflect planeary configurations that vary wildly from the configuration of our own solar system, what theories exist at present to account for the presence of epistellar giants and eccentric jovians. And, do those theories account for the fact that our own solar system has no Jovians inside of 5AU from the sun?

Also:

I've noticed that a number of jovians found outside of the Sol system traverse trajectories around their stars quite close to other Jovians, consider the Gliese 876 system, where two Jovian worlds are seperated by less than 1/3rd of an AU, do prevailing theories say that these jovians would have had to have formed much farther from the star than migrated inward?

I appreciate any feedback as always, Cheers.

[tony873004]

I don't know what the theories are, but I have my own guesses. I think that our solar system is very lucky to still have its original configuration. I think the extra-solar systems discovered to date probably formed looking a lot more "normal" (us being normal) and then evolved into their current states. Our galaxy contains hundreds of billions of stars, and probably as many brown dwarfs. As our solar system spends its billions of years orbiting the galaxy, from time to time, it may pass extremely close to another star. Passing less than 1/2 light day from another star would seriously and permanently disrupt the orbits of the planets. We'd end up with planets in eccentric orbits, random inclinations, and orbits that passed closer to each other than they could have during the formation stage. 2 Jupiters would not have been able to form in our solar system only 1/3 AU away. I think our solar system may have been lucky enough to avoid any close stellar passages, but such luck might not be the norm. Especially for stars that formed in clusters and spend the beginning of their lives in very close proximity to other stars before escaping to orbit the galaxy solo. These weird solar systems are easier to detect than a solar system like ours, so for the time being it's going to seem like weird is the norm. Next decade with NASAs new orbiting telescopes, we may have a much better answer as to what normal is.

[Apollo7]

Hmm interesting reply.

How to comment is another matter.

I do not know, at all, weather our solar system is normal or not. I'm hoping as you are that the next-gen crop of telescopes and interferometers (sp) will shed light on that very subject. At this point, -available- data would suggest our solar system is in the minority, however as you said current methods lend a greater chance of detection to unusual or highly massive solar systems and its likely we will find other starsystems like our own in the next, say, 20 years.

You say our solar system still is in the "original" configuration, well that is certainly -possible- but if indeed gas-giant migration can, and does happen in other places, it makes one wonder why it wouldn't happen here. Or if the gas giants condense out of the nebula like stars, what process causes them to form close together, or with eccentric orbits, or within 4 AU of their parent star. And whatever theory we come up with it has to account for why our system looks the way it does.

Here's another point: Consider the interesting duplicity in sizes and mass found in objects in our own solar system. Though with exceptions plainly visible, a good number of planets and moons in our solar system seem to "pair off". Consider: Earth and Venus, Uranus and Neptune, Io and Eruopa, Ganymede and Calisto, Ariel and Umbriel, Oberon and Titania. In each case you have two planets or moons with similar sizes and characteristics. This being said, it seems that such pairings are not present, or not immedately evident in the current crop of extra-solar planets, one might wonder why?

I guess for now speculation is all anyone can do, though I am trying to find just what the "experts" are saying, if anything on these matters. Cheers.