If you said "Nine, idiot. Everyone knows that." then you'd be wrong.
As of today, Pluto is no longer officially considered a planet.
There are only eight planets in the Solar System.
?? This must be what it feels like to change the number of stars on the flag. Somewhere there's a centenarian sitting around saying "I'll be damned if I'll ever use that new fangled 'Oklahoma' flag ... everyone knows there should only be 45 stars on Old Glory, idiot."
Then again, that same crotchy old jerk probably refused to accept Pluto as a planet originally anyway. So ...
I lost the point of what I was trying to say. Anyway, Pluto = space rock, not planet.