Missing member of planetary development discovered in the Kuiper belt

Beyond the orbit of Neptune, at approximately 30 to 50 astronomical units (AU, distance from the Earth to the Sun) from our central star, there are numerous small, medium, and large objects. They form the Kuiper belt – the waste dump for our Solar System, because the matter in this region couldn’t coalesce to form a proper planet. If current theory for planetary development is correct, the belt must contain bodies of all possible sizes.

The problem: first you have to find them. Larger object...