Reflecting on the Kuiper belt

Over the past 2 years, scientists have discovered that 7 of the roughly 500 known objects in the Kuiper belt–the reservoir of comets and other frozen objects just beyond Neptune’s orbit–have moons (SN: 5/4/02, p. 285: Elliptical duet rides the Kuiper belt). Several of the moons appear nearly as large as the bodies they circle.

According to a common theory, each moon was created when an interloping body smashed into a large Kuiper belt object.