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TimberWolf
2004-Sep-01, 04:34 PM
Hello,

With all the planet hunting going on in the last few years, I've heard that there are many Jupiter-size gas giants orbiting very close to their parent stars. Yet, most models of planetary formation that I know of state that at such proximities, the solar winds would blow away the lighter volatiles that make up a typical gas giant's atmosphere. Has there been any work on how such gas planets could form?

Cordially,

TimberWolf

Irishman
2004-Sep-03, 03:18 PM
The theory I've heard is that they formed farther out and then migrated inward. How? I don't know.

Brady Yoon
2004-Sep-07, 05:53 AM
The theory I've heard is that they formed farther out and then migrated inward. How? I don't know.

Could the planets become slowed down due to the friction in the solar system?

eburacum45
2004-Sep-07, 11:31 AM
Yes; the theory was previously that the giant planets formrd in a thick stellar nebula and then migrated in by friction, before stellar radfiation pressure cleared most of the nebula.

However I fail to see how this model can explain the two inner system giant planets in the 55 Cancri system...

My image of 55 Cancri e; a Hot Neptune? (http://www.forteantimes.com/forum/attachment.php?s=dcadc6c58d9babba4bbf0fb736e112af& postid=435736) as seen by Celestia...

TimberWolf
2004-Sep-08, 03:42 AM
Hello,

Hmmm. If these hot giants formed in the outer reaches of the nebular disk and subsequently fell towards the parent star, how did the giant stop itself from crashing into the parent star?

Cordially,

TimberWolf

eburacum45
2004-Sep-08, 12:03 PM
[homer simpson] I don't know[/homer simpson]

but I might be able to guess; the central star is a difficult place to get to, energy-wise; think how difficult it is to get to Mercury;
Messenger is taking six years and a very circuitous route.

So the friction effect, if it is responsible, may simply not be strong enough to slow the planet right down and make it fall into the star.

Ut
2004-Sep-08, 01:56 PM
It's also possible that there's simply less material close to the star, and the presence of a super gas giant is able to clear the area out completely. Remember, the planets aren't so much rubbing against the debris as they are absorbing it or flinging it away. The transfer of momentum slows it down. Once they've absorbed or removed all the surrounding material, they'll stop migrating.

gritmonger
2004-Sep-08, 02:28 PM
Hello,

Hmmm. If these hot giants formed in the outer reaches of the nebular disk and subsequently fell towards the parent star, how did the giant stop itself from crashing into the parent star?

Cordially,

TimberWolf

Moving an orbit is rarely an exercise in stopping and starting- it's momentum added or subtracted, which causes the orbit to change by a little. Subtracting some momentum by swapping it with another smaller planet that was flung into a further orbit, or worse yet out of the system entirely, would move the planet closer to the parent star. A few times with medium-sized planets, or once with a large planet would be enough.

Brady Yoon
2004-Sep-08, 11:14 PM
Hello,

Hmmm. If these hot giants formed in the outer reaches of the nebular disk and subsequently fell towards the parent star, how did the giant stop itself from crashing into the parent star?

Cordially,

TimberWolf


This is pure speculation on my part... Maybe most planets are destroyed as they fall into their star, and the ones that survive are there because the radiation pressure and stellar winds can clear away the solar system matter. :oops: