Reply #62: The definition does seem rather arbitrary [View All]

[Spearman87]

But kicking Pluto out of the solar system proper has a certain logic. It’s always been a strange outlier. If it were discovered today, now that we know so much more about the Kiper Belt and all the other distant objects out there, I think it would be classified as just a large Kiper Belt Object with little fanfare. Now we have a solar system proper with symmetry to it--four inner rocky planets and four outer gas giants, all revolving in a thin plane, and probably all formed by similar processes during same era. The history of Kiper Belt objects is more vauge. Some may have been “captured” by the sun rather than formed during the early life of the sun. And many will probably be discovered with erratic, irregular orbits, far outside of the plane of the regular solar system, like Pluto.