of rock and ice.  As these chunks smashed into each other, some of them stuck together.  Gravity drew more chunks to them.  They eventually became Pluto.

Why was it so hard to find Pluto?

    Pluto is very small and far away.  It would appear much dimmer than Neptune.  Pluto could have been any one of hundreds of thousands of dim stars in the sky.  To search for Pluto, astronomers took photographs of certain sections of the sky over several days.  Then they compared the photos to see if any dots of light had moved.  This was slow and difficult work.  Sometimes they'd find an object had moved, but that it had moved too far.  If an object moved very far between successive pictures, it meant the