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Swift
2004-Feb-11, 02:09 PM
I've been wondering about something for a while.

Many (most?) of the planets that have been discovered around other stars are gas giants in very close orbits around their parent stars. I understand that given the technique being used to discover them that this would be the easiest type to discover and that small, earth-like planets in earth-like orbits are probably below the current detection limit. So we might not be seeing the "true" census of planets around other stars.

Still, as I understand the present theories of planet formation (and maybe this is my lack of understanding) the gas giants should be forming far out in their solar systems, not in orbits closer than Mercury. So what gives, is there a working theory? Could it be that they formed further out and were perturbed to closer orbits? Could they form close in and if so could they then be pushed out to more Jupiter like orbits?

Just curious..

Amadeus
2004-Feb-11, 02:58 PM
Maybe it's just that Gas giants in close orbit are easyer to spot. Larger orbits would have a longer rotation and therefore the wobble will take longer?

AstroSmurf
2004-Feb-11, 03:13 PM
I have been told (i.e, this is hearsay) that Jupiter is actually rather unusual, and that we're fortunate it stopped moving inwards when it did. Under normal conditions, it would have travelled inwards fairly early during planetary formation to (I guess) somewhere between the orbits of Venus and Mercury, swallowing most of the the inner planets in the process.

And I have no clue whether this is true or not, so feel free to correct me.

ZaphodBeeblebrox
2004-Feb-11, 04:36 PM
Current Thought, is that Gas Giants form Early and Often, in the Parent Star's Outer Envelope.

They then begin to Spiral Inward, due to friction with the Birth Cloud.

When the Star reaches it's First Fusion Stage, the Fusing of Hydrogen into Deuterium in a Star the Mass of our Sun, The Star will shed this Envelope, as light pressure builds on its New Surface.

Any Remaining Gas Giants, then jostle for position amoung themselves, and the Half Formed Cores, that will later become the Terrestrial Worlds.

More information on this, can be found in the following thread:

http://www.badastronomy.com/phpBB/viewtopic.php?t=10934