We have a tenth planet...
space
Astronomers have discovered a tenth planet, Lila (see note on name below)... modulo the debate about what is considered a planet; for which I point you to Gibor Basri's great essay: Defining "Planet".
UPDATE [2005-07-30 07:54:47]: This NYT story, "Planet or Not, Pluto Now Has Far-Out Rival", says that the astronomers are informally calling this planet, Xena! (Although Lila is the name they formally submitted to the IAU)
UPDATE [2005-07-31 09:40:31]: The Caltech website has been updated to include a note that the name Lila is not necessarily the name that they submitted to the IAU.