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Fraser
2005-Sep-12, 05:39 PM
SUMMARY: The time frame for the formation of new planets appears to be getting shorter than previously believed. Astronomers have discovered gaps in protoplanetary disks that suggest there are gas giants forming there. One star, GM Aurigae, is a younger version of our own Sun and the gap in its disk is at about the same location as our own gas giant planets. Since GM Aurigae is only 1 million years old, these results challenge the traditional theories that planets slowly formed over many millions of years.

View full article (http://www.universetoday.com/am/publish/baby_picture_of_early_universe.html)
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Greg
2005-Sep-12, 09:39 PM
This is a powerful finding supporting the gravatational instability model of planet formation. I have always had some doubt in the back of my mind about dating the disc vs the star. What if the planet building process pre-dated the beginning of stellar fusion? Maybe these planets have been forming for a longer period of time then calculated. Perhaps this possibility might help salvage the formation of gas giants by accretion.
I still favor a hybrid model of planet formation. I believe gas giants form by gravatational instability and may even be able to form secondarily by accretion. I also believe that terrestrial planets form by accretion. If true then this implies that there is something different about the dynamics and/or composition of the disc where gas giants form to allow for this separate process of planet formation to occur quickly.