Astronomers have always felt uncertain about Pluto, the outermost planet in the solar system. It is suspiciously small, with less than half of the earth's diameter, and its orbit is peculiar. Instead of revolving in a near-circle around the sun as the other planets do, Pluto follows an eccentric ellipse, cutting across the orbit of Neptune, its sunward neighbor (which is 39 times the size of the earth). These deviations suggest that Pluto may not be a real planet.
Last week Astronomer Gerard Peter Kuiper (rhymes with piper) of the University of Chicago made another move toward demoting Pluto. Recent observations have...
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