QUESTION:
What year was the bright spot on Pluto discovered?

ANSWER from Marc Buie on May 26, 1996:
This is a pretty hard question to answer.  It's easy to say when we first saw
Pluto in pictures taken in 1930.  The bright spot on Pluto is more complicated.
Back in 1954, Pluto was first seen to change in brightness.  This change
is caused by Pluto's rotation.  When Pluto's is at it's brightest we know
that that part of Pluto's surface must be brighter than all the rest.  So
at that time we knew that there was a bright spot on Pluto's surface.  We
didn't really see it until the new Hubble Space Telescope pictures were
taken of Pluto, but we've known it was there all along.