Astronomy
The Kuiper Belt: Icy Bodies Beyond Neptune
Quick fact
The Kuiper Belt contains at least as much mass as Earth and may hold hundreds of thousands of objects larger than 100 kilometers across.
Why this is interesting
Beyond the familiar planets lies a vast ring of icy worlds—so large that Pluto is just one of its many residents. Why did we demote Pluto, and what else hides in this distant frontier?