MONTEREY, Calif., Sept. 8 (UPI) -- NASA astronomers used the Hubble Space Telescope to discover three of the smallest objects ever detected -- they're orbiting beyond Neptune and Pluto.
Each lump of ice and rock is roughly the size of Philadelphia and NASA estimates they may have been there since the formation of the solar system 4.5 billion years ago.
The objects reside in a ring-shaped region called the Kuiper Belt, which houses a swarm of icy rocks that are leftover building blocks, or "planetesimals," from the solar system's creation, according to the astronomers led by Gary Bernstein of the University of Pennsylvania.
Bernstein told Monday's meeting of NASA's Division of Planetary Sciences in Monterey, Calif., the study's big surprise was that so few Kuiper Belt members were discovered.
With the Hubble Space Telescope's exquisite resolution, Bernstein and his colleagues had expected to find at least 60 Kuiper Belt members as small as 10 miles in diameter -- but they only discovered three.
