S
siriusmre
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How many times have I (and a few others here) asserted that the core accretion model of solar system formation is in trouble? Now, it seems to be dead.<br /><br />Despite this recent puzzling finding, I'm sure that there will be some who will write this off as being just another "adjustment" in the standard model as a result of new data. Others, like me, point to this as clear evidence that the core accretion model has finally been falsified.<br /><br />From the recent SPACE.com feature article:<br /><font color="yellow"><b>For scientists who spend time thinking about how planets form, life would be simpler if gas giants like Jupiter and Saturn didn’t exist.</b><br /><br />According to the standard model of planet formation, called "core accretion," planets form over millions of years as enormous blocks of rock and ice smash together to form planetary embryos, called "protoplanets," and eventually full-fledged planets.<br /><br />Most scientists agree that core accretion is how terrestrial planets such as Earth and Mars were created, <b>but the model can’t convincingly explain how gas giant planets like Jupiter and Saturn came to be.</b><br /><br />One major problem is that developing gas giants through core accretion takes too long. <b>According to the best current models, the process requires several million years—longer than the typical observed lifetime of the stellar gas disks from which planets are born.</b><br /><br />The other main difficulty is the so-called "migration" problem. Protoplanets are not sitting stationary in the gas disks as they bulk up. <b>Due to gravitational interactions with the disks, the protoplanets swirl rapidly inwards toward their central stars in what scientists call "Type 1" migration.</b> Models predict that this death spiral can take as little as 100,000 years.<br /><br /><b>This so-called "migration" problem is the toughest challenge facing theorists trying to explain gas giant formation through core accretion</b>, said Alan Boss, a planet forma</font> <div class="Discussion_UserSignature"> </div>