arther even than Neptune, the eighth planet, we find frozen
bodies smaller than the Earth's Moon—the more than 100,000
objects forming the Kuiper belt, the frozen boundary of our solar system.
Recently astronomers of the International Astronomical Union decided to reclassify Pluto as
a dwarf planet because of its size and eccentric orbit. Periodic comets (comets that appear
at regular intervals) originate in the Kuiper belt. Nonperiodic comets, on the other hand,
come from the Oort cloud, a gigantic sphere surrounding the entire solar system.