DAD22, which children's encyclopedia do you have? We have a Children's Dictionary and DD loves it. I think the encyclopedia may be a big hit too!
Sorry I didn't see this earlier.
We have the DK First Encyclopedia, as well as the DK First Nature Encyclopedia. Both of those are well loved. We have a children's Atlas too, but that isn't as well loved.
I think the DK First Encyclopedia just went through an update. Mine still lists Pluto as a planet, and discusses the Concord as though it is still in use.
My daughter's interest in space has expanded to the planets too, now. I'm planning her first trip to the Air and Space Museum for this weekend. I just hope that she can enjoy it with so many other children there... she's very shy.
Edit:
I think I'm wrong about the update. Everything I see lists the publishing date as 2002.