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Jonathan Silverlight wrote:
In message , Ron Baalke writes The Keck Interferometer observations revealed a gap of 18 million miles between DG Tau and its orbiting dust disc. Akeson notes that of the extra-solar planets - planets orbiting other stars - discovered so far, roughly one in four lies within 10 million miles of the parent star. Since planets are believed to form within a dust disc, either DG Tau's disc has a larger-than-usual gap, or the close-in planets form farther from the star and migrate inward. I don't begin to follow that. Are they saying that three in four lie more than 10 million miles from their star, like the planets in our solar system? Then they are in the majority, and DG Tau is normal. It appears that they have taken into account the fact that the extrasolar planets discovered so far are all giants, and all the giant planets in our Solar System are much, much farther than 10 million miles from the Sun. With a gap of 18 million miles, the closest that a giant planet could form might be something like 25 million miles from its star. I'm slowly beginning to accept the possibilty that planets migrate inward, and comets are flung outward. I have always believed that the planets formed about where they are now, and the comets formed in the Oort Cloud. I'm not yet convinced that that is not so, but I'm headed in that direction. -- Jeff, in Minneapolis Oh, by the way: Your mother saw a hamster. .. |
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