The Kuiper Belt

• A disk of icy/rocky objects which extends past the orbit of Pluto: roughly 50-100 AU.

• Probably about 70,000 Kuiper Belt Objects (KBOs) over 100km across.

• Maybe Pluto and UB313 are just the largest KBOs??

• When objects are perturbed (e.g. by Neptune) can head into inner solar system. There, increased sunlight causes ice to melt and turn into gas - the comet's tail.